50 million year old volcano cluster near Sydney

Australia’s new ocean-going research vessel Investigator has discovered extinct volcanoes likely to be 50 million years old, about 250 km off the coast of Sydney in 4,900 m of water.

While scientists were searching for the nursery grounds for larval lobsters, the ship was also routinely mapping the seafloor when the volcanoes were discovered.

They haven’t been found before now, because the sonar on the previous Marine National Facility (MNF) research vessel, Southern Surveyor, could only map the sea floor to 3,000 m, which left half of Australia’s ocean territory out of reach.

From The Guardian

Scientists searching for lobster larvae on Investigator research vessel instead find cluster of four volcanoes thought to be about 50m years old

Four enormous underwater volcanoes, thought to be about 50m years old, have been discovered off the coast of Sydney by a team of scientists who were looking for lobster larvae.

The volcano cluster was spotted through sonar mapping of the sea floor by Investigator, Australia’s new ocean-going research vessel, about 250km off the coast.

 Position with the GeoGarage platform

The centre of the volcanic cluster is 33 31 S, 153 52 E, which is 248 km from Sydney Heads.

The cluster is 20 km long and six km wide and the seafloor 4890 metres deep, with the highest point in the cluster rising up to 3998 metres.

The four volcanoes are calderas, large bowl-shaped craters caused when a volcano erupts and the land around it collapses.
The largest is 1.5km across the rim and rises 700m from the sea floor.
The 20km-long volcano cluster is nearly 5km underwater.

Professor Iain Suthers, a marine biologist at the University of NSW, said the volcano discovery was made when the team was searching for nursery grounds for larval lobsters.
“My jaw just dropped,” Suthers told Guardian Australia.
“I immediately said, ‘What are they doing there and why didn’t we know about them before?’ It really backs up the statement that we know more about the surface of the moon than our sea floor.
“I’m elated. We went there to look at eddies in the east Australia current and it was completely serendipitous to find this volcano cluster. We can only just imagine what will be around the corner if we continue to scan this area.”

Scientists believe the volcanoes were created by a series of shifts in geological plates that caused Australia to split from New Zealand. Suthers said the area was thought to be “billiard-table flat” but the enhanced mapping capability of the Investigator unveiled the calderas.

The 94-metre Investigator was commissioned by the CSIRO in 2009 via $120m from the federal government.

The vessel, which undertook its first sea tests in March, can map the seafloor at any depth, whereas its ageing predecessor, the Southern Surveyor, was limited to 3,000 metres.

 Mapping the sea floor on RV Investigator

Australia has the third largest ocean territory in the world, but we've only mapped 12 per cent of it. The RV Investigator is using state of the art equipment and design to map the sea floor, to any depth.  

Professor Richard Arculus, an igneous petrologist and volcano expert at the Australian National University, said the Investigator’s mapping ability has unveiled an “enormously exciting” discovery.
“They tell us part of the story of how New Zealand and Australia separated around 40m to 80m years ago, and they’ll now help scientists target future exploration of the sea floor to unlock the secrets of the Earth’s crust,” he said.

The team of 28 scientists, led by Suthers, included researchers from NSW, Latrobe, British Columbia, Sydney, Auckland, Technology Sydney and Southern Cross universities.

The voyage left Brisbane on 3 June and arrived in Sydney on 18 June.

Suthers said it was “inevitable” that other undiscovered volcanoes were in the region, but the Investigator has funding to operate at sea for only 180 days a year.

For the rest of the year it is tied up at a wharf in Hobart.
“We should thank Canberra for the funding we do have but it’s frustrating to build a state-of-the-art vessel only to have it sitting in a wharf for six months of the year,” Suthers said.
“This is a vessel that Australia has been crying out for for decades. It’s an incredibly stable vessel for those of us who are seasick. Usually when you’re hit by four-metre waves you lose a couple of days of research because you’re vomiting.”

A spokeswoman for Ian Macfarlane, the industry and science minister, said the shortfall was because Labor “left absolutely no money in the budget” to operate the Investigator.

Heat is being stored beneath the ocean surface

see picture

From NASA

For much of the past decade, a puzzle has been confounding the climate science community.
Nearly all of the measurable indicators of global climate change—such as sea level, ice cover on land and sea, atmospheric carbon dioxide concentrations—show a world changing on short, medium, and long time scales.
But for the better part of a decade, global surface temperatures appeared to level off.
The overall, long-term trend was upward, but the climb was less steep from 2003–2012.
Some scientists, the media, and climate contrarians began referring to it as “the hiatus.”

If greenhouse gases are still increasing and all other indicators show warming-related change, why wouldn’t surface temperatures keep climbing steadily, year after year?
One of the leading explanations offered by scientists was that extra heat was being stored in the ocean.

Now a new analysis by three ocean scientists at NASA’s Jet Propulsion Laboratory not only confirms that the extra heat has been going into the ocean, but it shows where.
According to research by Veronica Nieves, Josh Willis, and Bill Patzert, the waters of the Western Pacific and the Indian Ocean warmed significantly from 2003 to 2012.
But the warming did not occur at the surface; it showed up below 10 meters (32 feet) in depth, and mostly between 100 to 300 meters (300 to 1,000 feet) below the sea surface.
They published their results on July 9, 2015, in the journal Science.

 Schematic of the trends in temperature and ocean–atmosphere circulation in the Pacific over the past two decades.

Colour shading shows observed temperature trends (°C per decade) during 1992–2011 at the sea surface (Northern Hemisphere only), zonally averaged in the latitude-depth sense and along the equatorial Pacific… 

source : Nature

“Overall, the ocean is still absorbing extra heat,” said Willis, an oceanographer at JPL.
“But the top couple of layers of the ocean exchange heat easily and can keep it away from the surface for ten years or so because of natural cycles.
In the long run, the planet is still warming.”
To understand the slowdown in global surface warming, Nieves and colleagues dove into two decades of ocean temperature records; specifically, they examined data sets compiled from underwater floats and other instruments by the Argo team at the Scripps Institution of Oceanography, by the World Ocean Atlas (WOA), and by Japanese scientist Masao Ishii and colleagues.
The JPL team found that for most of the decade from 2003–2012, waters near the surface (0–10 meters) of the Pacific Ocean cooled across much of the basin.
However, the water in lower layers—10–100 meters, 100–200 meters, and 200–300 meters—warmed.

The animated map at the top of this page shows the trends in water temperatures in various depth layers of the ocean as measured between 2003 and 2012.
Areas in red depict warming trends in degrees Celsius per year, while blues depict cooling trends.
Warming is most acute between 100–200 meters in the western Pacific and the eastern Indian Ocean. Some areas of the Pacific appear to cool—particularly near the surface and in the eastern half, which correlates well with the cool phase of the Pacific Decadal Oscillation (PDO), which has been underway for much of the past 15 to 20 years.

Note that the Atlantic Ocean does not show significant trends at any depth, with warming temperatures in one place counter-balanced by cooling in others.
The Atlantic basin is also relatively small compared to the Pacific and does not have as much impact on global temperatures.
The JPL team also noted that the temperature signal was neutral or inconclusive at depths below 300 meters, where measurements are relatively sparse.

The figure below depicts the trends in a different way.
It represents a cross-section of the top 300 meters of the global ocean and how temperatures changed from 1993 to 2012.
Note how there are cooler waters near the surface in several years in the 2000s, but that waters at depth grow much warmer.
Note, too, how the overall trend in 20 years goes from a cooling ocean to a significantly warmer ocean.

Nieves, Willis, and Patzert were provoked to launch the study because they wanted a more detailed, nuanced picture of ocean temperatures than is possible with most models.
On a broad scale, models can replicate broad and long-term trends in the sea; but on smaller scales of space and time, a lot of the models cannot match real-world conditions.
The new findings should help improve models of ocean heat storage and climate impacts on regional scales.

The Pacific Ocean covers nearly one-third of Earth’s surface, so it has an outsized impact on the global thermostat.
“As the top 100 meters of the Pacific goes, so goes the surface temperatures of the planet,” said Patzert, a climatologist at JPL.
With the surface layer of the ocean being cooler for much of the study period, those waters had a moderating effect on air masses and weather systems on the continents.
However, ocean and air temperatures have started to rise swiftly in the past two to three years, which suggests that the cool phase of the PDO and the warming hiatus is over.

“Natural, decadal variability has been with us for centuries, and it continues to have big regional impacts on society,” said Nieves, a JPL scientist with a joint appointment at the University of California, Los Angeles.
“We can expect to have more hiatuses in the future, but unless future hiatuses are stronger than usual, they will be less visible due to fast rising greenhouse gases. Right now, the combined effect of the human-caused warming and the Pacific changing to a warm phase can play together and produce warming acceleration.”

Trailer : The finest hours

Disney has released the trailer for a new movie based on the true story of heroic US Coast Guard rescue of 32 mariners aboard the SS Pendleton.

In the winter of 1952, a four-man crew from the USCG braved 60-foot waves and 70-knot winds to save men trapped in stern section of the oil tanker after one of the worst Nor’Easter gales on record tore the vessel in two.
Using only a 36-foot wooden motorized boat the men carried out one of the most daring rescue missions in Coast Guard history.

"Coast Guard photo of bow section of tanker PENDLETON grounded near Pollock Rib Liteship, six miles off Chatham, Mass on the morning of Feb. 19, 1952."
Official USCG Photo;  by Richard C. Kelsey, Chatham, Mass.

The incident occurred on February 18 while the tanker was underway off of Cape Cod.
In the early morning hours fierce snow fall and hues waves snapped the vessel in two.
The captain and seven crewmen sank in the bow section of the ship.
Reports after the accident said the tanker had been constructed with “dirty steel”, which was not able to withstand gales force winds.

The Finest Hours recounts this amazing story from the perspectives of the US Coast Guard men that carrying out the operation as well as the desperate mariners stranded aboard the mangled tanker.  

Ice & sky : investigating the depth of time

Ice & sky website

Claude Lorius (born 1932) is a French glaciologist.

He began studying Antarctic ice in 1957, and, in 1965,
was the first scientist to be concerned about global warming.

He was instrumental in the discovery and interpretation of the palaeo-atmosphere information within ice cores.

Links :

• YouTube: Claude Lorius: how we discovered we could read the history of the climate in the ice
• YouTube : La glace et le ciel (Trailer in French) / Vimeo

Philippines uses 18th-century English aristocrat's map to claim disputed islands

Panacot, circled, in the Murillo map (Library of Congress)
http://www.imoa.ph/imoawebexhibit/

From The Telegraph by Julian Ryall

Philippines government to take 1734 document to UN tribunal to support its demand that China leaves the Scarborough Shoal

A 281-year-old map from the collection of an English duke is to be put forward by the government of the Philippines to support its claim to islands in the South China Sea that are presently being fortified by China.
The Philippines government has said it will submit the map, drawn up in Manila in 1734 by Pedro Murillo Velarde, a Jesuit priest, to the United Nations Tribunal on the Law of the Sea in The Hague as soon as this week, according to the Vera Files website.
The map shows islands that are now known as Scarborough Shoals, marked as Panacot, as part of Philippines territory.

They are shown around 120 miles off the west coast of the main Philippine island of Luzon.

The map shows islands that are now known as Scarborough Shoals, marked as Panacot, as part of Philippines territory.

They are shown around 120 miles off the west coast of the main Philippine island of Luzon.

The map shows islands that are now known as Scarborough Shoals, marked as Panacot, as part of Philippines territory (Library of Congress)

The Philippine government is calling on the UN to recognise its claim to sovereignty over the islands and to call on Beijing to withdraw.
The map was sold at Sotheby's auction house in London in November at the request of the Duke of Northumberland.
The duke sold the map, along with around 80 other family heirlooms, after serious flooding affected his properties in April 2012. Media reports suggested that the duke faced a repair bill for £12 million after the waters subsided.
The map was put up for auction on November 4, with the Sotheby's catalogue describing the 44-inch by 47-inch engraved map as being "the first scientific map of the Philippines" of its time.
With light browning along the creases, the map is flanked by a series of 12 engravings depicting people in native costumes, a map of the island that is today known as Guam and smaller maps of cities and harbours in the Pacific.

A Filipino businessman shows a replica of a 1734 Philippine map

which included islands in the disputed waters.

Sotheby's estimated that the item would sell for between £20,000 and £30,000, but it quickly outstripped those predictions and was eventually sold for £170,500 to a Filipino businessman.

Mel Velarde, president of an information technology company called Now Corporation, said he first became interested in the map because he shared a family name with the priest who had first published it.
He told the Vera Files that his interest increased when he realised that it "proved" the Philippines' claim to the islands.
The bidding quickly reached the £80,000 limit that Mr Velarde had initially set himself.
But after a "vision" of Chinese soldiers occupying the islands, Mr Velarde said it "became a personal crusade" to buy the map because the Philippines' claim needs to be backed up by evidence.
Asked why he had paid so much for the map, Mr Velarde said, "There's a bully in the neighbourhood. He already took over our land."

Mr Velarde has decided to donate the original map to the National Museum but has had a number of copies printed.

He will present one of those copies to Benigno Aquino, the president of the Philippines, on June 12, the anniversary of the nation's independence.
Another copy will be delivered to the UN as Manila seeks arbitration in the territorial dispute.
The Philippines accuses China of seizing the islands in 2012, when ships of the two nations were involved in a stand-off.
When the smaller Philippine force had to withdraw, the Chinese occupied the islands.

 Scarborough Shoals in the GeoGarage platform (NGA nautical chart)

In January 2013, the Philippines requested international arbitration in the case and, the following year, submitted a 4,000-page dossier to support its claim of sovereignty.
Beijing has ignored requests to take part in arbitration procedures.

Links :

• CBSNews : A wealth of stories from the Murillo-Velarde map 
• TheMurilloVelardeMap
• BBC : South China Sea: David v Goliath as dispute goes to court
• IMOA : Historical Truths and Lies Scarborough Shoal in Ancient Maps
• Murillo mapa de las yslas Philipinas (1744)
• TheMapHouse : “A Chart of the China Sea and Philippine Islands with the Archipelagos of Felicia and Soloo”

Tiny plankton snacking on plastic is a big problem for the food chain

'I am Plankton" what do we eat for breakfast? from Five Films

World exclusive - filmed for the first time at Plymouth Marine Laboratory, we dyed microscopic pieces of plastic with fluorescent dye so you can see them being ingested by the plankton - scary stuff.

From CNET by Michelle Starr

The effect of plastic microbeads, as found in toothpaste and exfoliants, on microscopic marine life is unknown -- but we know now that the substance is likely ingested by zooplankton along with their diet of phytoplankton, thanks to a video by a team of filmmakers led by Verity White of Five Films. 

The footage was part of a short film by Norwegian filmmaker Ren Kyst about litter and coastal cleanups that won Atkins CIWEM Environmental Film of the Year from the Chartered Institution of Water and Environmental Management in the UK.

An estimated 8 million metric tons of plastic makes its way into the oceans every year, according to a study conducted by researchers at the UC Santa Barbara National Center for Ecological Analysis and Synthesis, published in the journal Science early this year.
Somewhere between 6,350 and 245,000 metric tons of tha plastic is floating -- which means the rest of it ends up somewhere beneath the surface.

And it's not all plastic bottles, six-pack rings and fishing nets.
A lot of the plastic that ends up in the ocean comes from the plastic microbeads found in body wash and other personal care products.
Other discarded plastics degrade pretty quickly, eroding into very small fragments.
And, while it is estimated that plastics cause the death of over a million seabirds and 100,000 marine mammals every year, the effect it has on life under the ocean is difficult to gauge.

 Zooplankton and flourescent plastic microbeads.
Screenshot by Michelle Starr/CNET

The Plymouth Marine Laboratory in Plymouth, England is studying the impact these microplastics have on marine life, with a particular focus on zooplankton.
It was at the PML that White and her team shot the film.

The action takes place in a single drop of water over the course of about three hours, condensed down into less than a minute of footage, reports New Scientist.
Several copepods -- a type of zooplankton -- were surrounded by microscopic fluorescent polystyrene beads.
Copepods feed by moving their legs to direct food towards their mouths.
While they can reject the wrong type of phytoplankton (algae), the film clearly shows some of the beads get caught up and ingested by the animals.
This can cause problems for the zooplankton, as the plastic can remain in their bodies for up to seven days.
This negatively impacts the rate at which the zooplankton can consume algae, which in turn could impact their ability to survive.
This, according to the film, is a cause for concern not just for the zooplankton, but for other species as well. Zooplankton are at the bottom of the food chain, so if zooplankton populations drop, the animals that eat zooplankton will have a harder time finding food.
Moreover, what zooplankton ingest often ends up ingested by their predators, all the way to the top of the food chain.
The Plymouth Marine Laboratory has released this week a suite of videos and other educational materials on the impact of microplastics on the ocean.

Ocean-going spiders can use their legs to windsurf across water

Body-morphing spiders sail on water

From New Scientist by Andy Coghlan

Sailors and travellers, including Charles Darwin aboard HMS Beagle, have often reported seeing "ballooning" spiders flutter from the air into the sails of their ships, far away from any shore.

Dispersing spiders are known to use strands of silk to remain airborne in gusts of wind, but what happens if they are swept offshore and land in water?
We thought they would drown, but it turns out they are as adept at sailing as they are aeronautics.

"It was like an illusion," says Morito Hayashi of London's Natural History Museum, who first noticed common UK spider species sailing in the lab.
He was studying their flight, trying to figure out how they take off when he spotted the sailing behaviour.
"I was amazed that these common spiders, found in everyone's gardens, had such skilful sailing behaviour that no one had noticed before."

Water tolerance and tiptoeing.

The relationship between tiptoeing, sailing and the ability to float on water.

All tiptoeing individuals were also sailors, except for two individuals, suggesting that the sailing behaviour is almost completely associated with, and possibly a requirement for, the aeronautic behaviour

"One of the most amazing things is that no one had noticed this behaviour before," says his colleague Sara Goodacre of the University of Nottingham, UK.

Some species of spider form diving bells out of silk to enable them to breathe under water, while others are known to catch and eat fish.

But until now, no one realised that common spiders can sail, probably because the species that do it are small, typically just a couple of millimetres long.

"Water was always thought to be the ultimate barrier to dispersion," says Goodacre.

"Now, we know they can survive in water, so with this get-out-of-jail card, they can move far greater distances than we thought."

To find out how they do it, Goodacre, Hayashi and their colleagues observed the sailing skills of 325 spiders of 21 species caught at random on islands in ponds and lakes in various nature reserves around Nottingham in the UK.

Back in the lab, they placed individual spiders on small water trays and then used small air pumps to expose the spiders to breezes of between 3 and 80 centimetres per second.

All the spiders were able to stand on water thanks to their water-repellent legs.

And 201 of them, covering most species, showed off sailing skills.

 Spider behaviour on water surface. Sailing behaviour: linyphiid (a, c) and tetragnathid (b, d) spiders moving on the water surface with their legs (a, b) or abdomen (c, d) used as sails. When the abdomen was used the behaviour was referred to as upside-down sailing. A spider can sail stably even on turbulent sea salt water. Anchoring behaviour: use of silk as anchor to slow down or stop movement on water surface by linyphiids (which dropped the anchoring silk) (e) and the tetragnathid (which dragged the anchoring silk after it caught a floating object) (f). Each scale bar represents 1 mm

source : BMC series blog

Most attempted to catch the wind and cruise forward by making "sails" from parts of their bodies. Some pointed two forelegs up in a V-shape, while others thrust their abdomen skyward – the equivalent of a handstand on the water.

When exposed to a breeze on solid ground, they showed none of the behaviours, which suggests these are used specifically for sailing.

The spiders sailed just as well on salt and fresh water, and were able to manoeuvre even in turbulent water.

Some also created the equivalent of an anchor by throwing out strands of silk for attachment to surfaces, such as the side of the water tray.

They may use these to haul themselves onto objects from water, or onto a suitable landing spot.

Goodacre thinks that size is a limiting factor – only those not too heavy can skim across the water – which means this behaviour is not common.

"I'd say the limit is probably around 5 millimetres long," she says.

Her team now hopes to show that spiders sail in natural conditions, too.

Also, they want to examine what this means for evolution and geographic dispersion, given that spiders may be able to travel much further than thought.

"This may help explain why spiders are among the first species to colonise new habitats like islands," says Stefan Hetz of Humboldt University in Berlin.

"Spiders were thought to colonise exclusively by air; maybe they are good sailors too."

Rainbow of fluorescent corals found—Why do they glow?

Deep beneath the waves of the Red Sea, scientists have discovered corals that fluoresce in a range of colors, likely because it helps their algae friends.

From National Geographic by Carrie Arnold

Deep beneath the surface of the Red Sea, a rainbow of glowing corals have been discovered that's unlike anything scientists have ever seen.
"I was indeed surprised to find such a great color diversity at these greater depths," said Jörg Wiedenmann, a marine biologist at the U.K.'s University of Southampton.
Wiedenmann was especially amazed because the shallow-water corals on the same reef only give off a green color. (See more stunning coral pictures.)

Corals generally get their glow from fluorescent pigments that act as sunblock.
The sun's intense rays, which can sunburn swimmers and divers that flock to these reefs, cause similar damage to coral and zooxanthellae, the symbiotic algae that lives inside coral.
Although bright sunlight at shallow depths can make the pigments hard to see with the naked eye, they can be visible if the coral makes lots of them, says Wiedenmann, who led a new study on the corals published June 24 in PLOS ONE.

Though these pigments are well studied, scientists hadn't looked much at fluorescence in deeper dwelling corals, since they're not as exposed to sunlight.
Which begs the question: Why were the Red Sea corals so colorful?

Rainbow Bright

In 2014, Wiedenmann teamed up with Israel's Interuniversity Institute for Marine Sciences to study mesophotic reefs—or those reefs that are between 100 feet (30 meters) to more than 330 feet (100 meters) deep—near Eilat, Israel (map).
At these depths, very little sunlight reaches corals.
The few lightwaves that do make it this far are almost all in the blue range, the other colors having scattered.
(Also see "As Oceans Heat Up, a Race to Save World's Coral Reefs.")

The fluorescence of this Lobophyllia coral can change from green to red when exposed to blue or ultraviolet light.

Photograph by Professor J Wiedenmann

The researchers found that some of the corals at these depths glowed an intense green or orange. After photographing them in their natural environment, Wiedenmann packed samples of 16 different species of coral into plastic bags and brought them back to his lab in England for further study.

When Wiedenmann illuminated the corals with blue or ultraviolet light—mimicking what's found in the ocean depths—he found that they could also glow red or green.

Interestingly, Wiedenmann also discovered that the corals could produce these pigments in the absence of any light at all.

(Watch: Go beneath the waves and see coral reefs in living color.)

This, combined with the general lack of sunlight at these depths, means that these pigments weren't acting as a sunscreen.

Instead, the researchers believe that the pigments help make more light for their symbiotic algae, which need it for photosynthesis.

Happy algae translates to more oxygen and other benefits for the coral.

Red Sea corals glow in a rainbow of hues, a process that likely boosts the algae living inside them.

"To me, the most interesting part of the study is the range of colors you can find in very closely related species," Dimitri Deheyn, a marine biologist at the Scripps Institution of Oceanography who wasn't involved in the research.
He expected that similar corals would have similar colors, rather than the array that Wiedenmann found.
The corals' rainbow of hues is more than just a feast for our eyes—they may someday play a role in improving human health. Wiedenmann says that these pigments could help scientists do everything from tagging certain types of cells to look at them under the microscope to helping physicians better see cancer cells in the body.

The Atlantic slave trade in two minutes

315 years. 20,528 voyages. Millions of lives.

Watch the interactive map in action

From Slate by Andrew Kahn and Jamelle Bouie

Usually, when we say “American slavery” or the “American slave trade,” we mean the American colonies or, later, the United States.

But as we discussed in Episode 2 of Slate’s History of American Slavery Academy, relative to the entire slave trade, North America was a bit player.
From the trade’s beginning in the 16^th century to its conclusion in the 19^th, slave merchants brought the vast majority of enslaved Africans to two places: the Caribbean and Brazil.
Of the more than 10 million enslaved Africans to eventually reach the Western Hemisphere, just 388,747—less than 4 percent of the total—came to North America.
This was dwarfed by the 1.3 million brought to Spanish Central America, the 4 million brought to British, French, Dutch, and Danish holdings in the Caribbean, and the 4.8 million brought to Brazil.

This interactive, designed and built by Slate’s Andrew Kahn, gives you a sense of the scale of the trans-Atlantic slave trade across time, as well as the flow of transport and eventual destinations.
The dots—which represent individual slave ships—also correspond to the size of each voyage.
The larger the dot, the more enslaved people on board.
And if you pause the map and click on a dot, you’ll learn about the ship’s flag—was it British? Portuguese? French?—its origin point, its destination, and its history in the slave trade.

The interactive animates more than 20,000 voyages cataloged in the Trans-Atlantic Slave Trade Database.
(We excluded voyages for which there is incomplete or vague information in the database.)

The graph at the bottom accumulates statistics based on the raw data used in the interactive and, again, only represents a portion of the actual slave trade—about one-half of the number of enslaved Africans who actually were transported away from the continent.

There are a few trends worth noting.
As the first European states with a major presence in the New World, Portugal and Spain dominate the opening century of the trans-Atlantic slave trade, sending hundreds of thousands of enslaved people to their holdings in Central and South America and the Caribbean.
The Portuguese role doesn’t wane and increases through the 17^th, 18^th, and 19^th centuries, as Portugal brings millions of enslaved Africans to the Americas.

 West and West-Central Africa were the regions that supplied the majority of the slaves taken across the Atlantic Ocean in all periods of the transatlantic slave trade.

The image is of a map produced by Joan Blaeu in 1662.

It shows the Atlantic coast of Africa stretching from Senegambia to Angola in West-Central Africa. This map was an important source of information for many cartographers and writers trying to better understand the continent and even today it offers important information for historians of Africa.

The image is reproduced courtesy of Tracy W. McGregor Library of American History, Special Collections, University of Virginia Library.

In the 1700s, however, Spanish transport diminishes and is replaced (and exceeded) by British, French, Dutch, and—by the end of the century—American activity.
This hundred years—from approximately 1725 to 1825—is also the high-water mark of the slave trade, as Europeans send more than 7.2 million people to forced labor, disease, and death in the New World.
For a time during this period, British transport even exceeds Portugal’s.

In the final decades of the trans-Atlantic slave trade, Portugal reclaims its status as the leading slavers, sending 1.3 million people to the Western Hemisphere, and mostly to Brazil.
Spain also returns as a leading nation in the slave trade, sending 400,000 to the West.
The rest of the European nations, by contrast, have largely ended their roles in the trade.

By the conclusion of the trans-Atlantic slave trade at the end of the 19^th century, Europeans had enslaved and transported more than 12.5 million Africans.
At least 2 million, historians estimate, didn’t survive the journey.

 

Exploring reefs from space

NASA Earth Observatory images by Michael Taylor,

using Landsat 8 data from the U.S. Geological Survey. 

Caption by Audrey Haar and Mike Carlowicz.

Until recently, global maps of coral reefs had not changed much since the days of Charles Darwin.
The British scientist created some of the first maps in the 1840s, including observations from his ocean expeditions.
French scientist Louis Joubin updated those maps in 1912, adding information from letters he received from people living near reefs around the world.

But it was not until the beginning of the 21st century that coral reef mapping caught up with modern technology.
It took the arrival of a high-quality satellite camera—the Enhanced Thematic Mapper Plus on Landsat 7—and a convincing argument.
The Landsat series of satellites was originally created to observe landforms, so imagers on Landsat 1 through 5 were typically turned off while flying over large oceans in order to conserve power or limited data storage.
Ocean researchers eventually made the case to turn the instrument on over coastal waters and, occasionally, the open ocean.

 Vanua Levu in the GeoGarage platform (NGA chart)

From 2000 to 2003, scientists participating in the Millennium Global Coral Reef Mapping project collected and analyzed 1,724 Landsat 7 satellite images in order to create a uniform, global map of coral reefs.
The map has since been distributed openly on the Internet and has been adopted by researchers and coral reef managers around the world.

Now the next generation of Earth-observing satellites is poised to significantly improve and update coral reef mapping.
The sensors aboard Landsat 8 were designed to have higher sensitivity to brightness and color than Landsat 7 (12-bit data versus 8-bit). Most significantly, the satellite can observe Earth in wavelengths that allows scientists to adjust for the distortions caused by the atmosphere near the coast (a new shortwave, ultra-blue band at 0.43-0.45 micrometers supplements the blue band at 0.45-0.51 micrometers).
This extra sensitivity has made it easier to spot coral reefs and to quantify their area and depth.
Scientists now have a tool for monitoring the health of coral reefs even in the most remote regions.

“The Operational Land Imager on Landsat 8 is allowing us to outline the reefs around the world and measure area and estimate depth in ways never possible before,” said Frank Muller-Karger, a professor of oceanography at the University of South Florida and a leader of the Landsat-coral mapping efforts.
Muller-Karger has been funded by NASA’s Applied Sciences to work together with the NOAA Coral Reef Watch program to develop new products for a coral reef alert program.
The large image and close-up above were acquired on May 10, 2015, by the OLI instrument on Landsat 8.
The images show the extensive coral reefs on the north shore of Vanua Levu, Fiji’s second largest island.
In addition to Landsat, Muller-Karger and colleagues can turn to several other satellites to measure conditions around reefs.
Satellite sensors like the Moderate-Resolution Imaging Spectroradiometer (MODIS) instruments aboard NASA’s Terra and Aqua satellites can sense ocean temperatures, a key variable in the healthy development of corals.
Similar readings are being collected by the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument on Suomi NPP and the Advanced Very High Resolution Radiometer (AVHRR) instruments on NOAA’s Geostationary Operational Environmental Satellites.

The next big leap in coral studies may come from hyperspectral imaging.
New instruments tested on satellites, the International Space Station, and research aircraft have shown the potential to observe at more wavelengths and much better spatial resolution.
Such sensors might someday be able to spot minor variations in coral reef color—a sign of coral bleaching due to warming waters and changing ocean chemistry.
“You need Earth-observing cameras with small pixel sizes that allow a closer look at the corals. The scale needed is much less than 100 meters,” said Nima Pahlevan, a scientist at NASA’s Goddard Space Flight Center.
“With VIIRS and MODIS, for example, the best achievable spatial resolution is 250-500 meters We need instruments capable of resolving reefs at scales ranging from 1 to 40 meters.”

Humpbacks feast on a billion sardines!

A truly amazing sight is the arrival of a billion indian oil sardines, amassing to over three miles long they can confuse their predators but one of them is unavoidable...

Taken from Wild Arabia

Links :

• YouTube : A natural wonder: The Sardine Run /  Watch great sardine run / Underwater Fireworks -- Journey to the South Pacific

Oceans face massive and irreversible impacts without carbon cuts – study

The risks currently being experienced across the planet.

Most, if not all, are set to increase.

Regional changes in the physical system and associated risks for natural and human-managed systems.

Source: Science; Gattuso et al. (2015) modified from IPCC WGII AR5 (2014).

From The Guardian I / II

Business-as-usual carbon emissions would cause global warming that brings serious ocean acidification, death of corals and mangroves, scientists say

Time is rapidly running out for the world’s oceans and the creatures that live in them as the Earth’s climate continues to warm, say scientists.
Only “immediate and substantial” reductions in greenhouse gas emissions can hope to prevent “massive” impacts on marine ecosystems, warn the experts.
Researchers compared the fate of the oceans under two scenarios, one a “business-as-usual” approach and the other involving drastic cuts in emissions.
Their analysis showed that business-as-usual would have an enormous and “effectively irreversible” impact on ocean ecosystems and the services they provide, such as fisheries, by 2100.

Even after curbing emissions of carbon dioxide (CO2) enough to prevent temperatures rising by more than 2C compared with pre-industrial levels, many marine ecosystems would still suffer significantly, they said.

The international team led by Dr Jean-Pierre Gattuso, from the Laboratoire d’Océanographie de Villefranche in France, wrote in the journal Science: “Impacts on key marine and coastal organisms, ecosystems, and services from anthropogenic (man-made) CO2 emissions are already detectable, and several will face high risk of impacts well before 2100, even with the stringent CO2 emissions scenario.
“These impacts are occurring across all latitudes and have become a global concern that spans the traditional north/south divide.”
Any new global climate agreement that fails to minimise the impact on oceans will be “incomplete and inadequate”, stressed the scientists.

 Changes in ocean physics and chemistry and impacts on organisms and ecosystem services according to stringent (RCP2.6) and high business-as-usual (RCP8.5) CO2 emissions scenarios.

The findings are intended to inform the forthcoming 2015 United Nations climate change conference in Paris.
By 2050, the loss of critical habitats such as coral reefs and mangroves was expected to contribute to “substantial declines” for tropical fisheries, on which many human communities depended, said the researchers.

This was the case even under the 2C emission cutting scenario.
While Arctic fisheries may benefit from warmer temperatures at first, the scientists pointed out that this region was a “hot spot” of ocean acidification.

It also contained communities that were highly reliant on the sea.

Acidification, warmer oceans, sea level rise threaten the all marine ecosystems...in that video, the Ocean Initiative 2015 Project provides straightforward answers to this issue.

A new paper just published in Science summarizes the projected impacts of climate change on the world’s oceans, and consequently on humans and our economy.

The study concludes that global warming beyond the international limit of 2°C above pre-industrial temperatures would pose serious threats to marine ecosystems and their millions of human dependents.

It builds on the consensus science published by the Intergovernmental Panel on Climate Change last year.

The study concludes,
Ocean changes associated with a 2°C warming of global surface temperature carries high risks of impacts and should not be exceeded.

The oceans have absorbed over 90% of the excess heat and 28% of the carbon pollution generated by human consumption of fossil fuels. 

As the authors of the paper note, in many regions, the ocean plays an important role in the livelihood and food supply of human populations.

The ocean represents more than 90% of the Earth’s habitable space, hosts 25% of eukaryotic species, provides 11% of global animal protein consumed by humans, protects coastlines, and more.

‘Irreversible change’ to sea life from CO2
A major report warns that life in the seas will be irreversibly changed unless CO2 emissions from industrial society are drastically cut.
Twenty-two experts in the journal Science say the oceans are heating, losing oxygen and becoming more acidic - all in response to our carbon dioxide.
The scientists in Germany have been studying an event five million years ago that could throw light on today's challenges.

The study considers human impacts on the world’s oceans under two different scenarios.

The first is a business-as-usual high fossil fuel consumption scenario (called RCP8.5 in the latest IPCC report), and the second is a scenario in which humans take immediate serious steps to curb fossil fuel consumption (called RCP2.6).

Between now and 2100, RCP8.5 involves 6 times more global carbon pollution emitted by humans than RCP2.6.

The societal effort involved in reducing fossil fuel consumption and carbon emissions to meet RCP2.6 is obviously much greater than the effort involved in the do-nothing scenario, but this study finds that the outcomes are also starkly different for the world’s oceans.

In the business-as-usual scenario, by 2100 the oceans would be about 30 cm higher, oxygen content nearly 2% lower, ocean acidity 70% higher, and sea surface temperatures about 2°C hotter than in RCP2.6.

The authors write,

In summary, the carbon that we emit today will change the Earth System irreversibly for many generations to come. The ocean’s content of carbon, acidity, and heat as well as sea level will continue to increase long after atmospheric CO2 is stabilized. These irreversible changes increase with increasing emissions, underscoring the urgency of near-term carbon emission reduction if ocean warming and acidification are to be kept at moderate levels.

"Oceans - The sinks of our World": gives an example of how public engagement can make a significant contribution to scientific investigations of the effects of global warming and ocean acidification on marine life.

The film introduces us to a man who has been recording the temperature of the sea in his region of the Mediterranean Sea for forty years.

Now he is also collecting water samples to support scientific investigations on ocean acidification.

His work is of great importance to scientists who are studying the impacts of increasing emission of CO2, driven by human fossil fuel combustion, on the temperature and chemical make- up of our oceans.

Questions about the impact ocean acidification may have already caused to the health and diversity of marine life need to be answered.

However, questions about how the conditions for marine organisms may change in the future also matter greatly.

After all, experimental research in the laboratory and observations of marine life close to undersea volcanic vents have already shown that that calcifying organisms, such as chorals, are greatly affected by an increase of acidity in the water.

The film invites the viewer to observe scientific investigations in the laboratory but more so to join scientists as they conduct their investigations at under water sites.

(EUSEM)

As an example of one consequence of these changes, many marine species are shifting to different geographic regions as the oceans warm.

These shifts can pose serious challenges for fisheries.
Recent studies strongly reiterate that many species—including various invertebrates, commercially important fish species and marine mammals—are undergoing phenological and geographical shifts of up to 400 km per decade as a result of warming.

These geographical species shifts are projected to occur about 65% faster in the business-as-usual scenario than under RCP2.6.
Coral reefs are particularly sensitive to human-caused ocean changes.

They provide habitat for almost a quarter of the species in the oceans.

Hundreds of millions of people rely on the coastal protection, tourism, and food provided by coral reef ecosystems.

However, the authors of this study note that the dual threats of global warming and ocean acidification pose a serious threat to coral reefs.

Reef-building corals are extremely vulnerable to warming.

Warming causes mass mortality of warm-water corals through bleaching as well as through biotic diseases, resulting in declines in coral abundance and biodiversity.

Coral reefs can recover from bleaching events when thermal stress is minimal and of short duration.

However, ocean warming and acidification are expected to act synergistically to push corals and coral reefs into conditions that are unfavorable for coral reef ecosystems.

There is limited agreement and low confidence on the potential for corals to adapt to rapid warming.

The study also estimates some of the economic impacts of ocean changes in the business-as-usual scenario.

For example, lost coastal habitats and sea level rise could combine to expose 0.2 to 4.6% of the global population to inundation annually at a cost of 0.3 to 9.3% to global GDP.
In terms of tourism dollars, the difference between the two scenarios amounts to about $10 billion per year, hitting Australia and the USA particularly hard.
Loss of coral reefs to tourism under the RCP2.6 and RCP8.5 scenarios could cost between US$1.9 billion and US$12 billion per year, respectively. 

Coral reef losses due to ocean warming and acidification on the Great Barrier Reef place up to $5.7 billion and 69,000 jobs in Australia at risk.

In addition, ocean acidification may cause an annual loss of reef ecosystem services that are valued up to US$1 trillion by 2100.

For about a quarter of countries with reef-related tourism, mainly less developed countries, this kind of tourism accounts for more than 15% of gross domestic product and is more sustainable than extractive livelihoods.

The study also makes a critical and often-overlooked point.

Some people believe geoengineering is a better or more practical solution than curbing our carbon pollution.

Geoengineering proposals often involve slowing global warming by reducing the amount of sunlight absorbed by the Earth, for example by pumping sulfur high into the atmosphere, or putting large mirrors into orbit.

However, these proposals wouldn’t curb human carbon emissions, and hence wouldn’t slow the accumulation of carbon in the oceans, or the resulting ocean acidification.
Ultimately, the authors warn that immediate action to cut carbon pollution is critical if we want to curb the rapid and dangerous impacts already being observed in the world’s oceans.
…immediate and substantial reduction of CO2 emissions is required in order to prevent the massive and effectively irreversible impacts on ocean ecosystems and their services that are projected with emissions scenarios more severe than RCP2.6. Limiting emissions to below this level is necessary to meet UNFCCC’s stated objectives. Policy options that overlook CO2, such as solar radiation management and control of methane emission, will only minimize impacts of ocean warming and not those of ocean acidification.

Links :

• BBC : CO2 emissions threaten ocean crisis

Oceans could be headed for marine industrial revolution

A map of United States marine protected areas.(Photo Credit: NOAA)

 From Sea Technology

History repeats itself, and according to a new report, the same patterns that affected species extinction on land could be happening in the global oceans.
Despite this trend, however, we can help shape the future of ocean life by advocating for more marine protected areas and being an informed consumer.
Sea Technology spoke with Douglas McCauley, a University of California, Santa Barbara scientist who worked on the report, about what terrestrial species extinction means for marine life and the industrialization of the oceans.

Marine defaunation: Animal loss in the global ocean

How many land-based species have gone extinct?
In the last 500 years, there have been about 500 species of terrestrial animals that have gone extinct. There are many more that have gone extinct prior to 500 years, but some of the record keeping gets harder to do when you move back thousands of years.
What we are trying to do is focus on extinctions that are driven by people.
It's easier to concentrate on the past five centuries, where we know much more about what has happened to the environment.
In the ocean, in the same time period, 15 animals have been lost.

Why is the trend of species extinction on land important when looking at marine life?
It is a way for us to get a sense of how history can inform the future.
Things are basically behind in the oceans, in terms of our impact on wildlife communities, relative to our impacts on land.
It seems that we run through a couple of different transitions in the way that we influence wildlife.
When we look back at what happened on land, we can see how these transitions took form and what the consequences were.
We started hunting animals directly.
Then, we switched over to using the resources and space that animals use, hunting their homes and degrading their habitats.
That transition toward moving from hunting directly to hunting the land they use happened about the time, in a serious way, of the Industrial Revolution.
It was during that period where we were degrading habitats more rapidly that we also saw a major elevation in rates of terrestrial animal extinction.
In the oceans, the clock is turned back.
We're still hunting animals directly.
What we report is that there may be early signs of going toward this same shift in the ocean.
If we look at a wide range of data sources from marine industry, it seems there is a lot of new growth in development in the oceans.
We are now beginning to use space in the oceans at unprecedented rates.
That may be pushing us toward a period where we begin to industrialize our use of space in the oceans.

You mention a marine industrial revolution.
Is this shift what that refers to?
Exactly.
The terrestrial Industrial Revolution was about building out our cities and factories and using resources from wild spaces.
That seems to be what we are seeing early signs of in the ocean.
We are building power plants in the oceans.
We're beginning to set ourselves up to start mining in the oceans.
There are more than 1 million square kilometers of seabed that have been set aside for future mining. We're beginning to farm in an almost industrial-strength way.
It seems like some of the signs in these data remind us of the early days of the terrestrial Industrial Revolution.
As an ecologist, that's where we get a bit worried, because we saw this explosion of growth go hand-in-hand with major extinction rates.
We don’t want that to happen in the oceans.
We need to be careful about where we put this industry and what rates we let it develop.

In your research, how do you correlate human actions and species extinction?
The nice thing is, with only 15 animal extinctions in the oceans, there is not a lot of ambiguity.
You take an animal like the Caribbean monk seal, one of the more charismatic marine animals that was driven extinct.
It was just hunting.
We can look at historical records.
We arrive, and we start directly hunting the seals.

Future extinctions get a bit more complicated.
The major shift is that climate change is going to be a challenge in the oceans.
We are making the oceans more acidic and warmer, and that's a new source of stress that these animals have to cope with.
So, if their populations are getting low, they have to work though the process of adaption to a new environment.

So much of the ocean is unexplored. How does that play into your research?
The oceans are incredibly difficult places to study and understand.
This is the reason why a report like this is new.
We have been talking about these extinctions that are taking place on land, and the science is so much easier to document on land.
Doing it in the ocean is a lot harder.
First of all, this report is coming out a little late because of the challenges describing these patterns of change in the ocean.
They can only be incomplete views.
This is the best distillation of information from so many different sources, yet it remains a pretty incomplete view of what's happening out there with marine wildlife.

What can we do to help preserve marine species?
There are some big things and some small things.
Put more parks in the ocean.
Everybody knows that protected areas, parks on land, are the places you go to see wildlife.
Marine wildlife also thrives in parks.
We have far fewer protected areas in the oceans than we have on land.
We simply need more.

We need to address climate change.
It doesn't help us to set aside space for wildlife if we are heating up that space and acidifying it.
You don't think about a connection between what kind of miles-per-hour rating your car gets and oysters or tropical fish, but there is in fact a connection.
Everything that we do in our daily lives to reduce carbon emissions is going to buy marine animals time.

Use less plastic.
There are five trillion pieces of plastic in the oceans.

The last thing I'd say is don't eat endangered wildlife.
Use one of the smartphone applications to sort through your seafood section to figure out which are the rhinos of the sea.

Links :

• NYTimes : Ocean Life Faces Mass Extinction, Broad Study Says

Europe is set to get colder: Melting sea ice could weaken the Gulf Stream and cause temperatures to plummet

 

 The Gulf stream and climate change

The global conveyer belt is part of the large-scale ocean circulation that is driven by differences in the density of the waters.

It plays a key role in keeping the climate at balance and Europe warm.

Global warming may change it forever with unforeseeable consequences. 

From DailyMail by Victoria Woollaston

• Researchers studied winter weather data from between 1958 and 2014
• They found ice in Iceland and Greenland seas has reduced in past 30 years
• As sea ice retreats, air-heat exchanges that regulate climate are affected
• And this could leading to colder temperatures along the Western Europe
• Scientists have not specified how much temperatures could be affected

As climate change warms enormous portions of Earth, melting sea ice may actually cause Europe to become colder, a study has claimed.
Over the past 30 years, ice levels in the Icelandic and Greenland seas - regions key to regulating Earth's climate system -  have significantly reduced.
Scientists believe that in turn this loss of ice will cause the flow of warmer water from the tropics to be affected, weakening the Gulf Stream and leading to cooler temperatures in Western Europe.

 Over the past 30 years, ice in the Iceland and Greenland seas has significantly reduced (1900 to 1909 shown at (a), 1930 to 1939 (b), 1960 to 1969 (c) and 2000 to 2009 (d).) By reducing the size of these regions, the warmer water that travels up from the tropics is affected, leading to colder temperatures along western Europe

 'A warm western Europe requires a cold North Atlantic Ocean, and the warming that the North Atlantic is now experiencing has the potential to result in a cooling over Western Europe,' said lead researcher Professor Kent Moore from University of Toronto Mississauga (UTM)'s Department of Chemical and Physical Sciences.

Experts claim the disappearance of Arctic sea ice will lead to a reduction in cold, dense water - generated through a process known as oceanic convection - which flows south and feeds the Gulf Stream.

If this convection decreases, the Gulf Stream may weaken, thereby reducing the warming of the atmosphere.
The research, published in Nature Climate Change, is the first attempt to examine how changes in the air-sea heat exchange in the region are brought about by global warming.
The research also marks the first time researchers have considered its possible impact on oceanic circulation, including the Atlantic Meridional Overturning Circulation (Amoc).
The Atlantic Meridional Overturning Circulation (Amoc) is a major current in the Atlantic Ocean.
A flow of warm, salty water travels north in the upper layers of the Atlantic, while a colder flow of water moves south in the deep Atlantic.
Given its size and location on the planet, Amoc plays an important role in maintaining and controlling the Earth's climate system.

 The "cloud streets" over the Greenland and Iceland seas shown in this satellite image exist as a result of heat and moisture transfer processes that warm the atmosphere and cool the ocean
(NASA)

This is because it moves a large amount of heat energy from the tropics to the Southern Hemisphere towards the North Atlantic.
This heat is then transferred to the atmosphere and moderates the climate in this region.
As the heat is transferred, the water becomes colder and more dense and this sinks and travels back to the south and eventually rises again in the tropics.
This transfer of heat - known as an air-sea heat exchange - occurs in the Iceland and Greenland seas where the conditions are ideal for this convection to happen.
In particular, they each contain gyres that are shaped in such a way that make it easier for the hot water to rise and the cold water to sink in such a substantial way.
As the sea ice decreases, the distance between these two gyres and edge of the ice becomes wider and reduces the maximum region where the heat exchange can take place.
By studying data from between 1958 and 2014 taken from the European Centre for Medium-Range Weather Forecasts and model simulations, the researchers noticed this region is already 20 per cent smaller than 30 years ago.

As global warming heats the Earth and ocean, the retreat of the sea ice means there won't be as much cold, dense water, generated through oceanic convection (illustrated), created to flow south and feed the Gulf Stream. If convection decreases, the Gulf Stream may weaken and reduce the warming of the atmosphere

And if this decrease continues, they say it will weaken the overturning loop that feeds the North Icelandic Jet, thus reducing the supply of the densest water to the Amoc.
'The heat exchange is weaker - it's like turning the stove down 20 per cent,' continued Professor Moore. 'We believe the weakening will continue and eventually cause changes in the Atlantic Meridional Overturning Circulation and the Gulf Stream, which can impact the climate of Europe.'
The paper's other authors are Kjetil Vǻge from the University of Bergen, Robert Pickart from Woods Hole Oceanographic Institution and Ian Renfrew from the University of East Anglia.

Links :

• WashingtonPost : Melting Arctic sea ice could be disrupting the oceans circulation with potentially major consequences

Why time will stop for a leap second

With the advent of ever-more-accurate clocks,

keeping good time is becoming surprisingly complicated.
2015 June 30,     23h 59m 59s
2015 June 30,     23h 59m 60
2015 July  1,      0h  0m  0s 
(IERS)

From National Geographic by Jane J. Lee

Time will stop on June 30, but don't worry: It will only be for a second.
Researchers will add a sliver of time—a leap second—to the world's clocks.

An atomic clock based on cesium ticks away

at the German National Metrology Institute in northern Germany. 

Photograph by Focke Strangmann, AP

Just as leap years keep our calendars lined up with Earth's revolution around the sun, leap seconds adjust for Earth's rotation.
This kind of fine-tuning wasn't much of an issue before the invention of atomic clocks, whose ticks are defined by the cycling of atoms.
Cesium-based clocks, one kind of atomic clock, measure the passage of time much more precisely than those based on the rotation of our planet, so adding a leap second allows astronomical time to catch up to atomic time.
Most of us won't notice the addition, which happens at 23:59:59 coordinated universal time (UTC), or 7:59 p.m. ET, unless we deal in timescales shorter than a second, or if we use a computer program that crashes because it can't handle the leap second.
It's happened before: The 2012 leap second brought down Reddit, Gawker Media, and Mozilla.

"It's a major interruption mostly because there are a lot of systems that aren't prepared to handle the leap second correctly," says Judah Levine, a physicist at the National Institute of Standards and Technology (NIST) in Boulder, Colorado.
Leap seconds occur irregularly, which makes it hard for programmers to test their fixes, he explains.

Originally developed to study distant astronomical objects called quasars,
the technique called Very Long Baseline Interferometry provides information
about the relative locations of observing stations and about Earth’s rotation and orientation in space.
Credits: NASA Goddard Space Flight Center

Adding Time

Leap seconds don't come on a regular schedule because Earth's rotation varies, says Demetrios Matsakis, chief scientist for time services with the United States Naval Observatory in Washington D.C.
Our planet is slowing down, but it does so in unpredictable ways. So some periods require more leap seconds than others.

The International Earth Rotation and Reference Systems Service continuously monitors our planet and will recommend adding leap seconds to the International Telecommunications Union (ITU).
The ITU makes the ultimate decision on whether to add a leap second or not.
The last leap second was added in 2012, but in the early 1980s, time scientists were adding them every year, Levine explains.
Leap seconds were first introduced in 1972, and at that point, atomic clocks and astronomical clocks were already off by ten seconds, says Andrew Johnston, a geographer at Smithsonian's National Air and Space Museum in Washington D.C.
So researchers added ten seconds all at once in 1972 to the world's astronomical clocks, he explains.

 Earth's rotation is a part of defining time.

Leap seconds are added to our clocks to compensate for the Earth's slowing rotation.

Time to Pause

Levine is responsible for making sure the nation's timekeepers at NIST can handle the leap second. When it comes time to adjust their clock, NIST will transmit 23:59:59 UTC twice, Levine says. "Once when that time arrives, and once again for the leap second." So 6 p.m. mountain time—the NIST offices in Colorado are seven hours behind UTC—on June 30 will be stressful.
"There's a full panic mode just before and after 6 p.m.," he says.
Even if all goes well during the addition, Levine and his team are usually greeted the morning after by a deluge of emails concerning various problems.
Not everyone recognizes the leap second, although Apple does so on its devices.
Google mobile devices sync with Internet time services that are usually tied to atomic clocks.
But "if you have a standard Windows system, [it] just ignores the leap second," Levine says.
Financial markets like the New York Stock Exchange also take the leap second into account.
The exchange will close the market a half hour earlier than normal, at 7:30 p.m. ET on June 30, to help their systems deal with the addition.

Navigation services, like the U.S. Global Positioning System (GPS), never use leap seconds, Levine says.
That's because they need accurate measures of time in their calculations.
If they stopped their internal clocks for the leap second, they would get inaccurate positions.
The end-user isn't aware of this because the GPS system will still send information to the receivers we use—whether it's something we've picked up in an outdoor equipment store or our smartphones—about the leap second.
So we'll see the correct time on our devices.
But "true GPS time is off from civilian time by something like 16 seconds," says Levine.

As GPS time is global time reference based on atomic clocks it has no leap second mechanism and as such the time offset between the GPS and UTC times frames will change with every leap second event that occurs.

Since GPS time began on 1st January 1980 at 00:00:00 UTC, there have been 16 leap seconds applied to UTC to bring the time offset between the UTC and GPS time frames to 16 seconds. The next event in June this year will increase this time offset to 17 seconds.

The leap second correction affects all GNSS receivers, software and correction services which have to compensate for the additional second in their output messages, clock synchronization and position computations.

Dropping the Leap Second

The headaches caused by the leap second have prompted some to recommend doing away with it all together.
The organization responsible for deciding when to add a leap second has deferred making a decision on the issue but will discuss it again later this year, Levine says.
The Smithsonian's Johnston is "agnostic" about the leap second, although he knows plenty of engineers who would love to do away with it.
"But folks I know in the astronomy community would prefer to keep [leap seconds]," he says.
"Things seem to be going the direction of stopping leap seconds," Johnston says.
But people will have to wait and see what the International Telecommunications Union decides.
"My personal preference is that we stop doing this business," says NIST's Levine.
"The price for that would be atomic time would slowly walk away from astronomical time."
But it would only be about a minute or two difference over a hundred years.
Levine doesn't think that would be so bad.
Doing away with the leap second "would make my life easier."

Maritime Time Zones with GeoGarage API

Timezones are already a absolutely horrid mess,

and everybody actually tracking the leap second would in many ways be much much worse.

Links :

LiveScience : Why June 30 will be 1 second longer 

Fugro : GPS leap second 2015

Slate : Just a second

Wired : What's the deal with leap seconds?

Time : Why the upcoming ‘Leap Second’ could be a big headache for the Internet 

Google : "Leap smearing"