Saturday, April 7, 2018

The secrets of the sea revealed

From GoogleMapsMania by Keir Clarke

Robert Dudley was the 17th century author of Dell’Arcano del Mare.
This huge maritime encyclopedia covers all aspects of maritime life including shipbuilding, astronomy and navigation.
It also contains 130 beautiful maritime charts covering all parts of the world.

One of the 130 maps in his Secrets of the Sea is the Carta Particolare della Terra Nuoua con la Gran Baia et el Fiume Grande Della Canida, a sea chart of the Newfoundland era.

Norfish has created an interesting story map which explores some of the more interesting details in Robert Dudley's sea chart of Newfoundland.
As you progress through the story map Norfish examines the map's projection, calligraphy, place-name labels, prevailing winds and fathom soundings.

You can also explore the map for yourself.
Robert Dudley's sea charts are completely unique, enjoying a distinctive technical style with beautiful calligraphy and elaborate compass roses and cartouches.

Links :

Friday, April 6, 2018

France & misc. (SHOM) update in the GeoGarage platform

183 nautical raster charts updated

Why shipping needs to shape up for the climate

Greener ships for a sustainable future (IMO)
Shipping contributed about 3.1% of total annual carbon dioxide, or CO2, emissions in the period from 2007 to 2012, according to an International Maritime Organization study

From Greenpeace by Veronica Frank

It’s essential for transporting goods across the world, but the shipping industry has so far escaped strict regulations to clean up its climate-polluting emissions due to aggressive industry lobbying and a lack of public scrutiny.
You can now help change this.

After years of inaction, the International Maritime Organization (IMO), the UN body responsible for global shipping regulations, will meet in London on April 9 – 13 to finally agree on a plan to tackle the carbon emissions from ships.

While there are many things we can do to lower our own emissions – from cycling to saying no to single-use plastic or eating less meat – some things are further out of our hands, such as shipping.
But together we can give the IMO a massive wake-up call for the sake of the planet.

Did you know world’s 15 largest ships emit more pollutants than all of the world’s cars combined?
Nature and Biodiversity Conservation Union (NABU), a Germany-based environment association, has launched a campaign for a cleaner cruise industry.

Cutting emissions from shipping would play a key role in meeting the Paris Climate Agreement’s goals and here are five reasons why we need to put the spotlight on the IMO.
Shipping is a major contributor to climate change

Ships carry over 80% of world trade, using vessels that operate on marine fuels which are cheaper but dirtier than road transport diesel fuels.

source : American Chemical Society 2007

If the shipping sector were a country, it would rank sixth in the list of carbon emitters, just above Germany.
The sector’s emissions have been growing three times faster than global emissions and if left unchecked emissions could grow by 50-250% by 2050.
Aggressive lobbying and lack of public scrutiny has led to lack of action

The IMO is heavily influenced by the shipping industry, which has prevented the adoption of ambitious climate rules for the sector.
The lack of public scrutiny on the IMO – unlike other UN organisations – has helped the industry avoid emissions regulations.

The IMO’s transparency has been reviewed by anti-corruption organisation Transparency International, which found that weak IMO governance is delaying action on climate change.
The IMO’s April meeting can be the first step towards greener seas

At its meeting in London, we must ensure the IMO agrees on a high ambition plan to reduce shipping’s climate impact before a final deal is agreed in 2023.
Greenpeace is working with a coalition of NGOs to increase the sector’s climate ambition.
We urge the shipping industry to phase out emissions by 2050 at the latest and the faster the better.
No time to waste for low ambition

IMO membership is split between countries wanting to take climate action (such as the climate vulnerable Pacific island states and most of the EU states), those who want to lower ambition, like Japan, and those who are resisting any action, such as Brazil, India, Saudi Arabia and Argentina.

But climate impacts respect no boundaries and we’re already experiencing more extreme floods, droughts, hurricanes and heatwaves and the IMO needs to hear from you about the urgency of action!

A Satellite’s View of Ship Pollution
OMI is not the only satellite instrument observing NO2 levels in the atmosphere. 

The solutions are available.
We need industry-wide adoption

If ships are required to operate at lower speeds this could reduce emissions by a third and save fuel. Using carbon-free fuels and propulsion technologies, like wind-assisted propulsion, or battery-powered engines can also cut emissions and significantly reduce costs.

Greenpeace is already doing its small bit.
Our flagship the Rainbow Warrior is propelled by a two-mast structure with 1,255 m2 of sailing rig, large enough for a work vessel that also has a helideck.
We invested in the latest clean technology TIER 2 engines when it was built in 2010.

Imagine if, instead of using the cheapest and dirtiest fuel (so-called Heavy Fuel Oil) that poses serious health risks and could cause catastrophic damage in the Arctic, a worldwide ban was introduced on its use and transport through the Arctic, and the best in clean technology deployed across the entire shipping industry.

What can you do to help?

You can add your voice to those calling for a cleaner shipping industry by sharing the Cleaner Ships for a Safer World Facebook page here.

Links :

Thursday, April 5, 2018

The quest to map the mysteries of the ocean floor

From BBC by Adrienne Bernhard

The oceans’ floors are not a flat, sandy expanse – they are every bit as varied as the landscapes above water, with plunging valleys and huge mountains.
Making a map of them has been a challenging task.

Geologists have charted mountain ranges and forests and desert tundras, astronomers the heavens above, yet our planet’s oceans remain largely unexplored; it’s often said that we have a more complete understanding of the Moon or Mars than we do of our own seabed.

The $7 Million Shell Ocean Discovery XPRIZE is a global, three-year competition challenging teams to advance breakthrough technologies for rapid, unmanned and high-resolution ocean exploration.
The $1M NOAA bonus prize will be awarded to teams that demonstrate their technology can “sniff out” a specified object in the ocean through biological and chemical signals.
This will allow us to respond to emergencies, and discover new marine life and underwater communities in a way that never existed before.

The sea’s terrain plays a critical role in our ecosystem.
Underwater crests and valleys determine weather patterns and ocean currents; sea topography influences the management of fisheries that feed millions; miles of underwater cable connect billions more to the Internet; seamounts provide protection against coastal hazards such as approaching hurricanes or tsunamis, and may even offer clues to the prehistoric movement of the earth’s southern continents.

In 2017, an international team of experts from around the world, united under the non-profit General Bathymetric Chart of the Oceans (Gebco), launched the first effort to create a comprehensive map of the world’s oceans.

 Vertical relief of the Globe (1890)

While the earliest oceanographers trawled waters one painstaking knot at a time, recent advances in sonar technology mean that a single ship can now provide thousands of square kilometers’ worth of high-resolution maps during an expedition.

But the underwater discoveries that await aren’t only of interest to mapmakers or marine researchers.
Far below the ocean’s surface lies buried treasure: precious metals, rare earth elements, oil and diamonds – riches that have, until now, remained inaccessible to even the most intrepid of prospectors.

Some ecologists fear that a map of our sea floor will allow extractive industries the chance to profit from these resources, potentially endangering marine habitats and coastal communities in the process.
A global bathymetric map – that is, a map of the ocean’s floor – would certainly offer a better understanding of our blue planet, but it also might plunge us into a realm once reserved for science fiction: robot submarines, underwater volcanoes, sea jewels, coral with pharmaceutical properties, Wild West maritime law, toxic sediment plumes, and an ocean-based enterprise curiously devoid of humans or ships.
Once the map is made, will it be used as a tool for responsible management and conservation, or wielded like pirate’s bounty, a guidebook to extraction and exploitation?

 GEBCO_2014 bathymetric data coverage.
Note : at this scale, the World Ocean appears much better covered with ship soundings than it is.

Only 15% of the Earth’s ocean is mapped.
Zoom in on the middle of the Pacific in Google Earth, for example, and you’ll find a representation of the ocean floor based on satellite and gravity-derived bathymetry: low resolution, indirect, often inaccurate.
Considering that we’ve plotted our Solar System and charted the human genome, it’s rather astonishing that no map of the seafloor exists.
But the reason is simple: our planet’s oceans are vast, deep, and largely impenetrable, and water literally gets in the way.

For centuries, charting the murky depths meant braving the high seas, dangling plumb lines over the side of a ship, then drawing basic contours on cartographic maps.
Sailors etched soundings onto maps as early as the 16th Century, but no international standards for terminology or scale existed then, meaning early maps were not only rudimentary wayfaring tools, they were also confusing and contradictory.

It wasn’t until the turn of the 20th Century, an era marked by soaring interest in the natural world, that a group of geographers gathered under the leadership of Prince Albert I of Monaco to produce the first international charts of the ocean (what would eventually become Gebco).
Albert was fascinated by the then relatively new science of oceanography, and commissioned four research yachts to survey the Mediterranean.
More than 100 years later, Gebco and the Nippon Foundation formally announced Seabed 2030, a project that aims to map the entire sea floor by the year 2030 using data gathered from vessels around the world – including soundings from those early expeditions.

Modern ships like the kind used in Seabed 2030 are now outfitted with multibeam bathymetry, sonar systems that emit sound waves in a fan shape beneath a ship’s hull.
Each sonar ping measures the time it takes for a signal to reach the seafloor and return to the surface, a calculation of the water’s depth that can be marked as a coordinate on a grid.
“Multibeam extends the map area and gives us extended coverage,” explains Vicki Ferrini, the chair of Gebco’s subcommittee for undersea mapping.
Most ships already rely on sonar for obstacle avoidance and navigation, but vessels with multibeam dramatically increase the area of seafloor that researchers can ensonify – that is, the underwater footprint or track line they can capture with sonar.
“The process is a little like mowing a lawn with a riding mower versus a push mower.”

 Digital Elevation Model Central California

Part of the problem, however, is that ocean track lines are a lot like highways: certain parts of our oceans are heavily trafficked, while others may have no roads at all.
Continent-sized swathes of our planet’s seas are not regularly plied by ships.
One ship’s crossing between Hawaii and Japan, for instance, offers valuable track line data, but planned missions to more remote waters are equally important.
“A bathymetric survey done with modern multibeam is more than just driving a ship around the ocean,” says Rear Admiral Shepard Smith, director of the United States Office of Coast Survey at the National Oceanic and Atmospheric Administration (NOAA), a contributor to Seabed 2030.
“Sonar data is valuable, however; particularly in areas where we don’t have anything,” he says.
“In the Pacific or the Arctic, for example, individual track lines can be quite helpful to better understand poorly mapped areas.”

Gebco hopes to mitigate this problem by encouraging cargo ships, fishing boats and pleasure craft to participate in the project and transmit their data in real time, effectively crowdsourcing the underwater map.
The organisation also offers a “cook book”: a technical reference manual on building bathymetric grids, which can help developing nations make use of shared expertise.
Marine enthusiasts are even invited to submit name proposals for various underwater features – knolls, aprons, ridges, reefs, calderas, trenches, saddles, sills and salt domes, to name a few – by sending a letter to the International Hydrographic Organisation in Monaco.

The actual map is assembled at the British Oceanographic Data Centre in the UK.
Helen Snaith, the Global Centre lead for SeaBed2030, notes that “everyone from ocean modellers and researchers to policy makers and the general public can access the current data” via a marine iOS app.

Map of the southeast Indian Ocean, including many plateaus, ridges, valleys, and relatively flat abyssal plains. J. Whittaker

Perhaps no single modern expedition reveals the complexity of deep-sea ocean mapping more strikingly than the search for the missing Malaysian Airlines Flight 370 (MH370).
Investigators suspected that the plane, which vanished in 2014 en-route to Kuala Lumpur, had crashed in a remote area of the Indian Ocean.
The area was so poorly mapped, however, that search teams had to do basic mapping of the search area before they could draw up a more precise map with enough resolution to spot wreckage.

In fact, the search area was too deep to explore with ship-based mapping.
In shallower water, sonar-equipped towboats trail behind a manned vessel, but the Indian Ocean’s depth, monsoon climate and powerful currents made navigation of towed vehicles nearly impossible; instead, investigators dispatched a fleet of autonomous underwater vehicles, or AUVs.

Though underwater robotics is in its infancy, deep sea surveys have come to rely increasingly on submarines to scour the seabed for more detailed mapping.
“There are many advantages to AUVs,” explains James Bellingham, director of the Woods Hole Center for Marine Robotics in Massachusetts, USA.
“They are faster, they provide higher-resolution seafloor surveys, including hazard assessment, they lower upfront capital costs, and provide increased access to the ocean.” A proper multi-beam bathymetry system costs several million dollars and requires trained operators to sort the data, because ships, by definition, float on the ocean’s surface – not below it.
An AUV, by contrast, is less expensive and ideally suited to lonely, open stretches of water: researchers are currently designing new models that can be launched from land, and need to be powered only by batteries.
Of course, these assets can quickly turn into hazards: batteries need to be recharged, navigation systems must be tracked from nearby ships, and an AUV that breaks down must be brought back to port for service.
“In the future,” says Bellingham, “an autonomous surface vehicle might tow out underwater vehicles,” thus eliminating human beings from the at-sea aspects of mapping altogether.

Indian Ocean Floor by National Geographic Society
October, 1967 Based on bathymetric studies by Bruce C. Heezen and Marie Tharp of the Lamont Geological Observatory.
courtesy of David Rumsey
The Indian Ocean is known in ancient Sanskrit as Ratnakara, “the mine of gems”.
The name is indeed prophetic: hidden in the subsea mountains and valleys of that remote ocean are vast pools of resources, including rare metal alloys, oil, hydrothermal vents, even diamonds.
These aquatic riches are already on commercial radar, and a handful of ocean prospectors have begun to make their own high-resolution maps of the sea floor.
That data can be of value to researchers, Ferrini explains: oil, mineral and seismic companies might elect to contribute decimated, or lower resolution data, to Gebco’s map, thereby protecting their commercial interests while adding important information to the 2030 project.

Consider that De Beers Group, an international corporation and household name in diamond mining and retail, formed a partnership with the Namibian government over 20 years ago in pursuit of diamonds off the coast of that mineral-rich country.
More recently, De Beers added to its naval fleet several AUVs – part of a drill and crawler mining system that can scour the surface of the seafloor, loosen deep seabed sediment for rough diamonds and haul their cache hundreds of metres to the surface.
While shallow-water mining for sand, gold, tin, and diamonds is a decades-old enterprise, commercial deep sea mining is a new industry, its environmental impact yet unknown.
Scientists predict habitat degradation, slow and uncertain recovery, toxic plumes from surface ore, undersea noise, chemical spills in transport, and species extinctions.
A De Beers spokesperson confirms that the company “does not mine in areas considered to have high diversity of marine life,” and stated that, post-mining, “seabed recovery occurs naturally over a period of time and is assisted by the sediment that we return to the seabed.”

Still, the industry’s economic incentives often outweigh environmental safety concerns.
Rare earth metals found in deep sea alloys are used in everything from cell phones and DVDs to rechargeable batteries, magnets, computer memory and fluorescent lighting; and terrestrial oil reserves are being swiftly depleted, making the switch to deep sea wells an ever more tempting prospect.
“This is a race,” explains Bellingham.
“A race to get a baseline understanding of our ocean, before we change it dramatically.
We’ve lost that race already in the Arctic: life that used to live in sea ice no longer survives.”

Aside from the obvious effects of climate change, many of our shared waters have also become prey to urban ocean: seafloors riddled with pipelines, router cables and aquaculture, a trend that suggests we are all too eager to exploit our oceans before we properly understand them.

Map or no map, international maritime laws currently restrict deep sea mining more than 200 miles offshore – the point at which countries no longer have jurisdiction over their waters.
The United Nations Convention for the Law of the Sea is the legal framework that sets out the rights and duties of States in the use and exploitation of the oceans.
Article 76 of the convention repeatedly refers to the “continental margin,” the boundary between crustal provinces (that is, the physical outer edge of a country’s land) and the deep ocean basins beyond them; the law states that deep-sea life must be protected, and that revenue made from any mining venture there must be shared with the international community.

The deep ocean constitutes the largest and least understood biological habitat on Earth.
Two-thirds of our planet contains a marine wonderland of beauty and mystery.
These regions, characterized by extreme pressure, cold temperatures, and near-constant darkness are nonetheless home to an astonishingly diverse menagerie of creatures – the Dumbo octopus, the vampire squid, the ghost shark, spider crabs, coral and electric eels – bizarre organisms that display striking evolutionary adaptations.
Though these underwater denizens have changed little since the time of the dinosaurs, they are not terribly resilient, being slow to reproduce and highly sensitive to disturbance.

An international underwater atlas requires cooperation between stakeholders with various, sometimes competing interests, from government officials and oceanographers to military submarine operators, fishermen and offshore miners.
Once detailed bathymetric information is made available to the public, protective measures must be taken to protect both the map and the landscape it describes.

“A high-resolution map is an investment in responsible management of the seabed in the coming centuries,” says Rear Admiral Smith.
Indeed, we have but one planetary ocean, and its preservation depends on conscientious stewardship – particularly as we turn to its depths for the resources we can no longer find on dry land.
An underwater map might be the very sea change we need.

Links :

Wednesday, April 4, 2018

Seafloor map shows why Greenland’s glaciers melt at different rates

Rapid retreat : New seafloor data reveal that K√łge Bugt (shown) and other fast-retreating glaciers in southeastern Greenland sit within deep fjords, allowing warm Atlantic Ocean water to speed up melting.

From ScienceNews by Carlyn Gramling

Greenland is melting rapidly, but some glaciers are disappearing faster than others.
A new map of the surrounding seafloor helps explain why: Many of the fastest-melting glaciers sit atop deep fjords that allow Atlantic Ocean water to melt them from below.

Greenland Basal Topography BedMachine v3 is published by British Antarctic Survey.

Researchers led by glaciologist Romain Millan of the University of California, Irvine analyzed new oceanographic and topographic data for 20 major glaciers within 10 fjords in southeast Greenland.
The mapping revealed that some fjords are several hundred meters deeper than simulations of the bathymetry suggested, the researchers report online March 25 in Geophysical Research Letters.
These troughs allow warmer and saltier waters from deeper in the ocean to reach the glaciers and erode them.

Free-air gravity anomalies (red to blue) in southeast Greenland overlaid on a shaded relief of the 30 m resolution latest version of the Greenland Ice Mapping Project (GIMP) DEM.
Ocean Melting Greenland multibeam echosoundings are in shaded relief on a color scale from blue (deep) to orange (shallow).
Green diamonds are Ocean MeltingGreenland conductivity-temperature-depth (CTD) measurements. Glacier symbols mark the stability of the present front
(unstable = triangle and stable = circle), size of symbol is proportional to the balance flux, and color qualifies the retreat(red = retreat, blue = no retreat on a sill, and green = no retreat, not understood). AW = Atlantic Water

Other glaciers are protected by shallow sills, or raised seafloor ledges.
These sills act as barriers to the deep, warm water, the new seafloor maps show.
The researchers compared their findings with observations of glacier melt from 1930 to 2017, and found that the fastest-melting glaciers tended to be those more exposed to melting from below.

Ice retreat :  in 1932 (left), the front of the Mogens North glacier extended farther seaward than it did in 2013 (right).
New data reveal that the seafloor is much deeper beneath the glacier than thought.
National History Museaum of Copenhagen (L), Hand Henrick Tholstrup (R)

The study uses data from two NASA missions — Operation IceBridge, which measures ice thickness and gravity from aircraft, and Oceans Melting Greenland, or OMG, which uses sonar and gravity instruments to map the shape and depth of the seafloor close to the ice front.
The OMG mission also involves dropping hundreds of probes into the ocean each year to measure temperature and salinity at different depths.

Scientists have long suspected Greenland’s melting may be accelerated by the ocean (SN Online: 7/6/11), but needed data on fjord depth and glacier thickness to prove it.

The high-resolution OMG datasets, in particular, reveal bumps and troughs in the seafloor that were previously unknown, says glaciologist Andy Aschwanden at the University of Alaska Fairbanks, who was not involved with the study.
“Those small details can make quite a difference to when a glacier will retreat.”

Greenland ESA Greenland Ice Sheet ice flow and topography map
from 4000 ESA_EO Sentinel1 A & B acquisitions in 2015-2016, and CryoSat altimetry

What lies beneath

Some of Greenland’s glaciers, such as Mogens North (top), have retreated rapidly, while others, such as Skinfaxe (bottom), remain relatively stable.
New seafloor data reveal that some fjords, such as the one beneath Mogens North, are deeper (solid black line) than previous simulations suggested (dashed pink line).
The data also show a land bump, or sill, at the mouth of Skinfaxe glacier, which prevents warmer, deep Atlantic water (yellow on temperature bar) from reaching the ice.
Light blue represents the region in which the glacier’s ice front has advanced and retreated over time.

R. Millan et Al/Geophysical Research Letters 2018

Links :

Tuesday, April 3, 2018

US NOAA layer update in the GeoGarage platform

3 nautical raster charts updated

Lines of Longitude explained, with maps

Photo: Thesevenseas via Wikimedia, CC 3.0

From ScienceTrends by Daniel Nelson

You’ve probably heard of latitude and longitude before.
They’re the lines that divide the globe up into different regions, and points on the earth are specified by where the two types of lines intersect.
Without the longitude system, we wouldn’t be able to do many important things, like orient ourselves on the globe or calculate time zones.
A close examination of longitude which shows why this form of measurement is so critical to our lives and society.

Before delving into why longitude is so important, let’s be sure we have our definitions straight.
You may have confused longitude with latitude or vice-versa, so it’s important to know which lines on the globe are latitude and which are longitude.
Latitude is the system of measurement that runs east to west across the globe, diving the Earth into north and south.
It divides the earth into two hemispheres, with 90 degrees of latitude in the northern hemisphere and 90 degrees of latitude in the southern hemisphere.
The Equator, middle of the globe, is at 0 degrees latitude.
Longitude divides the globe into east and west halves, centered on a line called the Prime Meridian, or 0 degrees longitude.
Every other line that runs north to south across the globe is known as a meridian, and it measures one degree of the entire Earth’s circumference.
There are 360 degrees of longitude total, with 180 being west of the Prime Meridian and 180 being east of the Prime Meridian.

courtesy of NASA

Why do we need the Longitude system?

The longitude system is necessary because we have to have a standardized way of tracking the passage of time across the globe.
It would be troublesome if people in one part of the world had no method of determining what time it was in another part of the world.
A longitude system is also important for ocean navigation, as being able to track the passage of time across the various time zones is necessary for orientation.
Scientists can use the system to help them calculate trajectories, monitor weather data, and engineer self-driving vehicles.

Map of Africa with lines of latitude and longitude.
Image: (Eric Gaba – Wikimedia Commons user: Sting) CC 3.0

These problems were understood by various explorers, traders, and mariners throughout the centuries.
Fortunately, tracking the movement of the sun provides a reliable way of measuring time.
The British Government passed the Longitude Act in the early 1700’s, an act which promised a substantial amount of money to the person who could design a way to track longitude at sea.
This problem was eventually solved by John Harrison, who invented a device called the marine chronometer which allowed sailors to determine their longitude position while at sea.
Even after chronometers were proven reliable, many cities and small towns still continued to set their clocks based upon sunset and sunrise.
The problem with this is the fact that variables like altitude impact sunrise and sunset, leading to a situation where cities located on roughly the same lines of latitude had different times.
This problem was compounded by the proliferation of railroads during the industrial revolution.
It was hard to coordinate the schedule of trains because each city would have its own time.
To solve this problem, nations began standardizing time zones based, more or less, upon lines of longitude.

Maritime Time Zones with the GeoGarage platform

One place on the globe had to be chosen as the Prime Meridian, and it was eventually decided that the city of Greenwich would be used as the location for the Prime Meridian.
This is why the Prime Meridian is often called the Greenwich Meridian and the world’s standard time is Greenwich Mean Time (GMT).
The now international 24 hour system developed out of this initial system, and now all time zones are based on the Prime Meridian and lines of longitude.

 A map of the world but it’s just the time zones.

In terms of calculating time with longitude, time zones shift (more or less) every 15 degrees.
Dividing the 360 degrees of longitude by 15 should result in 24 perfect time zones, though in reality time zone borders often follow political or geographical boundaries.
Some time zones even have offsets of only half an hour or 45 minutes.
This means there’s actually quite a few more time zones than twenty-four.
For every line of longitude that the sun passes, approximately four minutes pass.
Another notable line running north to south across the globe is the International Date Line.
The Date Line is about halfway across the Pacific Ocean, in between North America and Asia.
The Date Line isn’t straight, it curves around to avoid cutting across countries and certain political borders.
You need to add a day to your calendar if you cross the Date Line while going east to west, and you need to subtract a day if you cross it going west to east.

Image: Jailbird via Wikimedia Commons, CC 3.0

The degrees of longitude that make up the time zones are set approximately 60 nautical miles, 69 regular miles, or 11 kilometers apart at the equator.
This distance varies and shrinks as the lines of longitude move closer to the poles.
This happens because the Earth is widest at the Equator and becomes more narrow towards the poles, the meridians converge on one another at the North and South poles.
When it comes to calculating one’s global position, each degree of longitude can be divided into 60 minutes, and these minutes divided into sixty seconds.

The longitude of Seattle, Washington, for example, is:
122.3321° W. (122 Degrees, 33 Minutes, 21 Seconds West).
It’s this extremely precise system, when combined with the latitude system of measurement, allows people to figure out their exact place on the globe.
Without these measurements, Global Positioning Systems wouldn’t work.

This video demonstrates how to use observations of the sun combined with local and Greenwich time to determine longitude.
An interesting project for anyone interested in navigation and the geometry of our relationship with the sun.

Reading GPS Coordinates

To read GPS coordinates, know that the latitude coordinates will be presented first in the coordinates.
The lines of latitude run 90 degrees north and south, so check the N or S after the coordinates to see which hemisphere it is in.
The longitude coordinates are given after the latitude coordinates, with “W” representing points west of the Prime Meridian leading up to 180 degrees and “E” representing points east of the Prime Meridian, also leading up to 180 degrees.
Let’s look at the full GPS coordinates of a point in Seattle this time:
47.6062° N, 122.3321° W.
That’s 47 degrees North, 122 degrees West, 33 minutes, 21 seconds.
Now you can see that lines of longitude and latitude are important for both scientific research and our daily lives.

Links :

Gliders on the storm

From The Economist 

From sharks to ice shelves, monsoons to volcanoes, the scope of ocean monitoring is widening

In November 2016 a large crack appeared in the Larsen C ice shelf off Antarctica (pictured).
By July 2017 a chunk a quarter of the size of Wales, weighing one trillion tonnes, broke off from the main body of the shelf and started drifting away into the Southern Ocean.
The shelf is already floating, so even such a large iceberg detaching itself did not affect sea levels.
But Larsen C buttresses a much larger mass of ice that sits upon the Antarctic continent.
If it breaks up completely, as its two smaller siblings (Larsens A and B) have done over the past 20 years, that ice on shore could flow much more easily into the ocean.
If it did so—and scientists believe it would—that ice alone could account for 10cm of sea-level rise, more than half of the total rise seen in the 20th century.

The dynamics of the process, known as calving, that causes a shelf to break up are obscure.
That, however, may soon change.
Ocean Infinity, a marine-survey firm based in Texas, is due to send two autonomous drones under the Larsen C shelf in 2019, the first subglacial survey of its kind.
“It is probably the least accessible and least explored area on the globe,” says Julian Dowdeswell, a glaciologist at the University of Cambridge who will lead the scientific side of the project.

The drones set to explore Larsen C look like 6-metre orange cigars and are made by Kongsberg—the same Norwegian firm that runs the new open-ocean fish farms.
Called Hugin, after one of the ravens who flew around the world gathering information for Odin, a Norse god, the drones are designed to cruise precisely planned routes to investigate specific objects people already know about, such as oil pipelines, or to find things that they care about, such as missing planes.
With lithium-ion-battery systems about as big as those found in a Tesla saloon the drones can travel at four knots for 60 hours on a charge, which gives them a range of about 400km.
Their sensors will measure how the temperature of the water varies.
Their sonar—which in this case, unusually, looks upwards—will measure the roughness of the bottom of the ice.
Both variables are crucial in assessing how fast the ice shelf is breaking up, says Dr Dowdeswell.

The ability to see bits of the ocean, and things which it contains, that were previously invisible does not just matter to miners and submariners.
It matters to scientists, environmentalists and fisheries managers.
It helps them understand the changing Earth, predict the weather—including its dangerous extremes—and maintain fish stocks and protect other wildlife.
Drones of all shapes and sizes are hoping to provide far more such information than has ever been available before.

Saildrone, a Californian marine-robotics startup, is looking at the problem of managing fish stocks.
Its tools are robot sailing boats covered with sensors which it builds at something more like a factory than a shipyard on the island of Alameda in San Francisco Bay.
These 7-metre, half-tonne vessels—it has so far built 20 of them, one of which is shown on the cover of this quarterly—are designed to ply the seas autonomously, using carbon-fibre wings as their sails.
The wing has a fin attached to it which keeps it trim to the wind at all times.
Its on-board computer (which has a GPS-equipped autopilot), its sensors and its radio get their modest 30 watts of power from lithium-ion batteries topped up by energy from solar panels whenever the sun is out.

One of the first hubs deploying these drones is at Dutch Harbor on Amaknak Island in Alaska; at any given time three of the boats based there are off monitoring a large pollock fishery in the Bering Sea, something they can do autonomously for up to a year before returning for maintenance.
They gather data using echo-sounders designed by Simrad, a subsidiary of Kongsberg.
Because each species of fish reflects different frequencies of sound in its own way (often because their swim bladders resonate differently) a sonar which emits a wide range of frequencies, as the wideband Simrad devices do, can tell what is a pollock and what is not.

Never mind the pollock

The drones supplement the fisheries’ main survey ship, which counts the pollock at the beginning of every season in order to determine how many fish can be caught.
Their data give it a better sense of where to look.
Sebastien de Halleux, Saildrone’s chief operating officer, says they also find more pollock, providing a count 25% higher than that of the official survey vessel.
This may be because the drones cause less disturbance and drive fewer fish away.
In time he thinks the drones might go beyond helping the existing system and do the job on their own, which would be a lot cheaper.

Pollock are good to eat, and if fisheries are managed sustainably they will remain so in perpetuity.
But they are hardly the most exciting fish to monitor.
That honour must surely go to the great white shark.
Jayson Semmens, a marine biologist at the University of Tasmania in Australia, is using a new generation of sensor tags to study the behaviour of these fearsome fish in more detail than was possible before—not to protect people, as shark attacks are very rare, but to build a scientific understanding of their metabolism.
He uses accelerometer data from a tag the size of a grain of rice, attached to the shark’s fin with a clamp, to calculate the energy it expends when it breaches out of the water.

The tags are too small to have enough power to send their data straight back to base.
But they do not need to be retrieved directly from the shark (which is probably just as well).
Their attachments dissolve over the course of their life, so in time they float free, rising to the surface and emitting a simple signal that allows them to be found.
Armed with the data they record, Dr Semmens can calculate the fish’s total energy needs, and thus how much prey a single shark requires.
That can be used to gain an understanding of the flow of energy through the food chain, which is basic to understanding the dynamics of the ecosystem.
The flow of energy through terrestrial ecosystems is comparatively easy to study; marine ones are more mysterious.

A tiny sensor that measures a shark’s metabolism seems remarkable—but at heart it is no more so than a modern phone.
“The accelerometer I use to measure great white shark activity,” says Dr Semmens, “is the same one you use to turn your smartphone into a lightsabre.”
Such tiny tags, which can also measure the temperature and pressure of the surrounding water, are a big step up from the bulky tags of yesteryear, which would provide a single acoustic frequency that allowed researchers to follow the fish if they were close enough.
And they are improving rapidly.
“People are talking about tags which sample blood from animals underwater,” says Dr Semmens.

The same technology can be used for environmental monitoring as well as pure science.
Dr Semmens has tagged several endangered Maugean skate in Tasmania’s Macquarie harbour with somewhat larger sensors—they weigh 60 grams, instead of 10—that measure heart rate and the dissolved oxygen content of the water.
Parts of the harbour are becoming anoxic—deprived of oxygen—because of large-scale near-shore salmon farming.
The data from the skate show how much of this is going on, and how much harm it is doing.
That makes it easier to argue for changes that boost conservation efforts.

One of the biggest benefits of better measured seas is the possibility of getting to grips with dramatic weather events.
The top 3 metres of the oceans hold more heat energy than the entire atmosphere.
How much of that energy escapes into the air, and when and where it does so, drives the strength and frequency of storm systems.
And there is ever more energy to do that driving.
The average surface temperature of the seas has risen by about 0.9°C (1.6°F) in the past hundred years, according to America’s National Oceanic and Atmospheric Administration.
This means that, since the 1980s, about a billion times the heat energy of the atom bombs dropped on Hiroshima and Nagasaki has been added to the ocean—roughly an atomic explosion every few seconds.

Yet even as the amount of energy the oceans hold has risen, the details of its transfer to the atmosphere remain unknown for large swathes of the ocean.
This is particularly important when it comes to understanding something like the South Asian monsoon.
The rains are driven by the huge size of the Bay of Bengal and the amount of fresh water that pours into it from the Ganges and Brahmaputra river systems.
Because this buoyant fresh water cannot easily mix with the denser salty water below it, the surface gets very warm indeed, driving prodigious amounts of evaporation.
Better understanding these processes would improve monsoon forecasts—and could help predict cyclones, too.

That’s why it’s hotter under the water

To this end Amala Mahadevan of Woods Hole Oceanographic Institute (WHOI) in Massachusetts, has been working with the Indian weather agencies to install a string of sensors hanging down off a buoy in the northern end of the Bay of Bengal.

A large bank of similar buoys called the Pioneer Array has been showing oceanographers things they have not seen before in the two years it has been operating off the coast of New England.
The array is part of the Ocean Observatories Initiative (OOI) funded by America’s National Science Foundation.
It is providing a three-dimensional picture of changes to the Gulf Stream, which is pushing as much as 100km closer to the shore than it used to.
“Fishermen are catching Gulf Stream fish 100km in from the continental shelf,” says Glen Gawarkiewicz of WHOI.
These data make local weather forecasting better.

Three other lines of buoys and floats have recently been installed across the Atlantic in order to understand the transfer of deep water from the North Atlantic southwards, a flow which is fundamental to the dynamics of all the world’s oceans, and which may falter in a warmer climate.

Another part of the OOI is the Cabled Array off the coast of Oregon.
Its sensors, which span one of the smallest of the world’s tectonic plates, the Juan de Fuca plate, are connected by 900km of fibre-optic cable and powered by electricity cables that run out from the shore.
The array is designed to gather data which will help understand the connections between the plate’s volcanic activity and the biological and oceanographic processes above it.

A set of sensors off Japan takes a much more practical interest in plate tectonics.
The Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET) consists of over 50 sea-floor observing stations, each housing pressure sensors which show whether the sea floor is rising or falling, as well as seismometers which measure the direct movement caused by an earthquake.
When the plates shift and the sea floor trembles, they can send signals racing back to shore at the speed of light in glass, beating the slower progress of the seismic waves through the Earth’s crust, to give people a few valuable extra seconds of warning.
Better measuring of climate can save lives over decades; prompt measurement of earthquakes can save them in an instant.

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Sunday, April 1, 2018

Image of the week : Egg Island, Bahamas

Released 30/03/2018 10:00 am
Copyright contains modified Copernicus Sentinel data (2018), processed by ESA
perfectly captured the contrast between the shallow waters & the ocean 

From ESA

When it comes to eggs, most of us are probably thinking of the chocolate variety that we hope will pass our way this weekend, but they’re difficult to spot from space.
Instead, we can offer you this gorgeous Copernicus Sentinel-2B picture of Egg Island in the Bahamas.

 Egg Island with the GeoGarage platform (WLP nautical chart)

Covering just 800 sq m, Egg Island is officially an islet.
This tiny uninhabited patch is at the northwest end of the long thin chain of islands that form the Eleuthera archipelago, about 70 km from Nassau.
Its name perhaps originates from the seabird eggs collected here.

 zoom on Egg Island

The image, which Sentinel-2B captured on 2 February 2018, shows the sharp contrast between the beautiful shallow turquoise waters to the southwest and the deeper darker Atlantic waters to the northeast.
Ripples of sand waves created by currents stand out in the shallow waters.
These shallow waters are a natural nursery for sea turtles and other sea life.
Any disturbance to this delicate ecosystem could spell disaster for wildlife.
n fact, Egg Island was recently at risk of being developed as a cruise ship port, which would have meant dredging the seabed and destroying coral reefs.
Fortunately, this plan didn't take hold because of the damage it would cause to the environment.