Satellites trace sea level change

The animation shows regional mean sea level trends 1993-2010 as measured by radar altimeters.

Some regions experience a rise of up to 12 mm per year (dark red), while others see a decrease of about 12 mm per year (dark blue).

On average, the global sea level rises about 3 mm

From BBC

A major reassessment of 18 years of satellite observations has provided a new, more detailed view of sea-level change around the world.

Incorporating the data from a number of spacecraft, the study re-affirms that ocean waters globally are rising by just over 3mm/yr.
But that figure, according to the reassessment, hides some very big regional differences - up and down.
The Philippine Sea, for example, has seen increases in excess of 10mm/yr. 

Part of that signal reflects the great fluctuation in winds and sea-surface temperature across the Pacific Ocean known as the El Nino/La Nina-Southern Oscillation.

"The trend map is really a way of looking at average field changes over the 20 years," explained Steven Nerem of the University of Colorado, US.
"The places where you see high trends probably won't have high trends in another 20 years. "A lot of this is decadal variability that will average out over the longer time series, which is why we need more missions to understand where this variability is."

Paolo Cipollini from the UK's National Oceanography Centre added:
"Many of the features in the trend map indicate changes in heat storage and correspond to long-term variations in the ocean currents."

This is evident if you look for some of the well-established mass movements of water - such as the Gulf Stream arching across the North Atlantic from the eastern US, or the Kuroshio Extension reaching out from Japan into the Pacific

Scientists have reviewed almost two decades of satellite data to build a new map showing the trend in sea levels.

Globally, the oceans are rising, but there have been major regional differences over the period.

Surface bounce

The map was unveiled in Venice, Italy, at a symposium marking "20 Years of Progress in Radar Altimetry".

The research will help scientists to tease out the scale of the various contributions to long-term sea-level rise and understand better the annual and inter-annual changes that can occur.

Currently, the most significant contributions are identified as being the expansion of the world's oceans due to their absorbing more heat, and the melt water coming from eroded glaciers and ice sheets.

A key quest is to identify to what extent sea-level rise may be accelerating and to pull out any long-term oscillations in ocean behaviour that could confuse that signal.

 

   The Jason satellite series is a benchmark for this field of study

 

The study was completed as part of the Climate Change Initiative (CCI) agreed by European Space Agency (Esa) member states at their ministerial meeting in 2008.

The CCI seeks to deliver long-term observations on a large set of "essential climate variables" - sea-level change being one of the most important indicators of global change.

Measuring ocean surface shape from satellites has a relatively short history.
Routine observations began with Europe's ERS-1 spacecraft in 1991, and this has subsequently been followed up by a series of international missions.
The benchmark today is arguably Jason/Poseidon - a cooperative venture between the US and Europe (principally France).
Now in its third incarnation, the Jason satellite circles the globe making a topographic map of 95% of the Earth's ice-free oceans every 10 days.

To do this, it uses a radar altimeter, which constantly bounces microwave pulses off the sea surface.
By timing how long the signal takes to make the return trip, the instrument can determine sea-surface height.But to get a full picture, Jason's data needs to be tied into that from satellites which view parts of the world it cannot see, and also mapped on to tide gauge information.
Although these coastal stations cannot provide the same global view as space-borne instruments, they capture much longer trends.
Some gauge stations have unbroken records going back more than 200 years.

More detail

Another important tool introduced recently is the gravity satellite - specifically, the two US Grace spacecraft.
This duo can weigh the amount of ice held in Antarctica and Greenland, and the quantity of water stored on the continents.
They have provided new insights into the scale of melting at the poles, and the impact of changes in precipitation that can move huge volumes of water from the ocean to the land.

Esa recently lost its flagship Earth observation satellite, Envisat, after 10 years of unbroken data-gathering. 

The spacecraft and its altimeter stopped operating without warning in April, underlining the need for several instruments to be maintained in orbit at the same time.
A replacement altimeter should launch on the Sentinel-3 spacecraft at the end of 2014.
A continuity satellite for the present Jason is also expected to go up within months of the Sentinel.

Other types of altimeter are being built, as well.
In December this year, France and India should launch their Saral platform.
This will carry a high frequency (Ka band) altimeter that should capture better the changes occurring very close to coastlines - detail which is beyond the reach of microwave observations.

"The key challenge in the coming years is to ensure we keep acquiring altimetry data, that we are able to calibrate it and that we can ensure its quality," said Maurice Borgeaud from Esa's Earth Observation Science, Applications and Future Technologies Department.

"Also, we need to tackle the new domains of radar altimetry.
Coastal altimetry has been mentioned - also what you can do to measure water levels in rivers and lakes.
Again, the old generation of radar altimeters were not designed to do this; the latest generation will be."  

 
The modern tide gauge is now a highly sophisticated tool.
Coastal instruments have recorded sea level change at some locations for more than 200 years

 

The golden age of nautical charts - When Europeans discovered the rest of the world (BNF exhibition)

BNF exhibition : "l'âge d'or des cartes marines"

From BNF

The Bibliothèque nationale de France holds such treasures as scientific documents that take us back to the time of great discoveries

Reconstitution du planisphère de la géographie d'al-Idrîsî
Sicile, 1154. Copie du XIIIe siècle, Maghreb.

Arabs take up the work of the Greeks and revive the scientific tradition of cartography.

In the 12th century, the Arab geographer al-Idrîsî draws up a map of the world, bringing together most of the geographic knowledge of his time.

As the most extraordinary pieces, one can find the parchment and often enriched with gold illuminated nautical charts, called ‘portulans charts’ (from the Italian term ‘portolano’, book of nautical instructions).
These maps show the succession of harbours along the coasts; the rhumb lines dotted on the maps correspond to bearings as measured to relative north.
Thanks to this graphic system, navigators could find their way by writing down on the chart the distance they thought they had covered.

Atlas Miller
Carte de l'Insulinde et des Moluques

In contrast to the theological image of the world that the globe or map of the world provided, a new cartographic representation, developed as of the 13th century n the context of the expansion of maritime trade.

The oldest portulan chart would date from the late 13th century: it is the famous ‘Carta pisana’, housed at the Department of maps and plans.
Only a few portulans charts among the oldest ones have survived to this day. (ex.: Portolan chart of Guillem Soler (c.1380) / Portolan chart of Gabriel de Vallseca (1447)) : see BNF Gallica catalogue

Partie orientale du monde
Altas catalan, vers 1375

These are the "portulans" which, just as the Catalan Atlas, describe coast and harbour.

The BnF’s collection is the biggest in the world as it gathers five hundred portulans charts.
Both technical innovations and scientific objects, ‘portulans charts’ also represent the quest for faraway lands
 These often impressive polychrome works of art are spectacular; furthermore, they conjure up some sort of exotic universe.

 Globe terrestre, dit "Globe vert"
Martin Waldseemüller (1507)

The exhibition presents a selection of 200 main pieces: charts, globes, astronomy tools, objets d’art and ethnographic objects, stuffed animals, drawings, prints, paintings and manuscripts.

Atlantis pars Altera. Geographia nova totius mundi
Gérard Mercator (1595)

Research on projection, which allows representing the entire globe on a flat map, increases.

In particular, Mercator’s research, very useful for the sailors, comes to mind.

This Flemish geographer is one of the leading figures of the golden age of Dutch cartography.

These items belong to the BnF’s collections or are exceptional loans from the musée du Quai Branly, musée Guimet, musée du Louvre, Arts et métiers, Mobilier national, musée de la marine, Service historique de la Défense, British Library, Italian and French regional institutions.

L'Amérique septentrionale
Détail du globe terrestre (1681-1683)
Of both economic and political interest, cartography is important to states, particularly for military reasons.

The large globes of Coronelli, which allow contemplating the world such as it was seen in the 1680s by the Sun-King at the height of his glory, bear witness to the links which connect Prince and cartographer.

The exhibition focuses on various issues: sailing conditions and use of charts; discovery of Africa, Asia, Americas and the Pacific; rivalry of maritime powers; geographical knowledge transmission between the Indian Ocean and the Mediterranean sea; creation and dissemination of the iconography of the new worlds, its landscapes, peoples, customs, fauna and flora.

Magellan fait le tour du monde par l'océan

Battista Agnese, Atlas nautique

At the end of the 15th and the beginning of the 16th century, the great Spanish and Portuguese navigators broaden considerably geographic knowledge.

America appears for the first time on the world map

Links :

• BNF virtual exhibitions : The history of cartography / The Globes of the Sun King
  / The sea, terror and fascination / Press Release (in French but with many photos)

Image of the week : Tahiti, French Polynesia

>>> geolocalization with the Marine GeoGarage <<<

From NASA

In August 1768, Captain James Cook, naturalist Joseph Banks, and a shipload of sailors set sail from England to Tahiti to observe the Transit of Venus.
Camped out on Point Venus, they witnessed the event on June 3, 1769.
Cook sketched the transit, but Banks had surprisingly little to say about it.
Perhaps he was distracted by the wonders of the island itself.

The Enhanced Thematic Mapper Plus on the Landsat 7 satellite captured this natural-color image of Tahiti on July 11, 2001.

This island is part of a volcanic chain formed by the northwestward movement of the Pacific Plate over a fixed hotspot.
Tahiti consists of two old volcanoes—Tahiti-Nui in the northwest and Tahiti-Iti in the southeast—linked by an isthmus.
Through studies of its rock layers, geologists have figured out the likely history of Tahiti-Nui.
Today it is roughly round, and it was roughly round when it first formed as a volcanic shield between 1.4 million and 870,000 years ago.
But between then and now, it had a different contour.
Both the northern and southern flanks of Tahiti-Nui collapsed sometime around 860,000 years ago, gouging massive arcs out of the island’s perimeter
 Soon after the northern flank collapse, a second shield volcano began forming.
Volcanic material on the northern side of Tahiti-Nui eventually overtopped the original volcanic structure and started filling in the southern depression.
Although Tahiti-Nui now has a fairly symmetrical contour, it has an asymmetrical three-dimensional shape.
Mountains are taller on the northern half of the island.

Yet something else besides volcanic activity has shaped Tahiti: rain.
Heavy tropical rains have carved deep valleys, some with nearly vertical walls up to 1,000 meters (3,000 feet) tall.
The angled sunlight in this image brightens some slopes, while leaving others in shadow.
Tahiti’s sharp relief has complicated the geological surveys because they cause so much erosion.
But the same rains have also promoted the growth of the lush plants that carpet both Tahiti-Nui and Tahiti-Iti.

Though the Transit of Venus was the stated objective of the British expedition, Banks was likely more interested in Tahiti’s plants.
Specimens he collected from Tahiti, New Zealand, South America, Australia, and Java accounted for roughly 1,300 new species, and his famed collected is now stored at the Natural History Museum in London.
Complementing the rich life on land is marine life around Tahiti’s perimeter.
Coral reefs fringe the island, and the reefs are thickest on the southern and western sides.
Reefs frequently form along the submerged slopes of volcanic islands.

Surfing Mavericks : aerial footage

This clip is a sequence from the MacGillivray Freeman classic "Adventures in Wild California"

This incredible footage was shot by Greg MacGillivray, founder of the One World One Ocean campaign.

Genetically modified pet fish worries Florida environmentalists

GloFish's Electric Green Tetra may or may not have an unfair advantage in the wild.

From WP

Since Yorktown Technologies first sold its genetically modified pet — the GloFish — in 2003, the fluorescent fish, an altered variety of zebra fish, has become a popular aquarium item, with millions sold in various neon hues.

In February, Yorktown introduced the Electric Green Tetra, a genetically modified black tetra fish. Like its zebra fish cousin, the GM tetra is a small freshwater fish that includes genetic material from a fluorescent coral that makes it neon-bright. Under a black light, it glows in the dark.

The two GloFish are very different, however, in what environmentalists and some experts say is a crucial way: The heat-loving zebra fish is from southern Asia and can’t survive long in cooler U.S. waters; thus, the Food and Drug Administration has ruled that there would be little threat of invasion of U.S. waterways if it were released from home aquariums.
But the black tetra is native to South America and likely to be happy making a splash in the inland waterways of South Florida and Latin America.

In South Florida, the modified black tetras could upset an environment already burdened with 30 types of nonnative fish.
In South America, they could mean an undesirable interference in natural biodiversity.

“My worry is that they’ll be such a novelty that they will be imported back to [South America] and kids will let them go and they’ll start interbreeding with fish whose genomes are very similar,’’ said Barry Chernoff, a freshwater fish biologist and chair of the environmental studies program at Wesleyan University in Middletown, Conn.
“We would see the spreading of the fluorescent coral gene in the native fish.’’

 Genetically engineered angelfish (Pterophyllum) glow in a tank under a blacklight, at a fish farm in Pingtung, southern Taiwan on September 16, 2010.

The fish are the world's first fluorescent angelfish which were created by a joint project between Taiwan's Academia Sinica and Jy Lin, a private biotechnology company.

The breed is the largest fluorescent fish in the world which are able to mate and reproduce, said Yu-Ho Lin, Chairman of Jy Lin. The fish are expected to be sold at around $30 after certification. (REUTERS/Pichi Chuang)

Because pet fish are often let loose by owners who no longer want them, Chernoff and others say the threat is serious.

“The neotropical region contains the most diverse freshwater fish fauna and complex freshwater ecosystem in the world, with some 6,025 fish species so far recognized,’’ Gordon McGregor Reid, chair of the Wetlands International Freshwater Fish Specialist Group of the International Union for Conservation of Nature, said in an e-mail.
“We meddle with this at our peril.”

Yorktown’s chief executive, Alan Blake, said the company chose the black tetra to modify because it is nonaggressive and shows no tendency to be invasive.
“The black tetra has been sold for over 60 years and there has never been an ecological concern with it,’’ Blake said.

There have been reports of natural black tetras in Florida’s waters.
But Blake said there is no evidence that groups of them live there permanently; probably, he said, they are eaten by predators.

Blake pointed to research by Jeffrey Hill, who was part of the task force that reviewed Yorktown’s successful application to raise the GloFish tetra in Florida.
In a 2011 study, Hill found that largemouth bass and mosquito fish in Florida ate twice as many red GloFish as regular zebra fish when they were all put in tanks together.
“Florida is a predator-rich environment. [The GloFish] is considerably more vulnerable’’ than its non-modified counterparts, said Hill, a nonnative fish specialist at the University of Florida’s Tropical Aquaculture Laboratory.

That’ s not reassuring to environmentalists such as Chernoff.
“So their plan for not having these things take over the wild is predation by other species? Great,” he said.

Electric Green Tetra's swimming at night with blue LED.

Their DNA has been modified so they glo

An unfair advantage?

Breeding between escaped GloFish and native fish could weaken the progeny and negatively affect the native fish species in future generations, said Brian Zimmerman, aquarium curator at the Zoological Society of London.

The fluorescence in the GloFish may give them an unfair advantage or a disadvantage as they forage for food or in their roles as prey and predator, Zimmerman said.
The point is, nobody knows for sure. “GM fish have only been around for a few years, and I don’t think we know enough to say they are safe,” he said.

If GloFish tetras breed with wild black tetras, the fluorescent gene would be passed on for only a limited number of generations, said Eric Hallerman, a scientific adviser to Yorktown and chair of the Department of Fish and Wildlife Conservation at Virginia Tech in Blacksburg.

GloFish tetras reproduce at half the rate of regular black tetras, and the fry survive at 97 percent the rate of their natural peers, Hallerman said.
Furthermore, fluorescence takes energy and is a burden that makes the fish less fit, so it will be bred out, he said — eventually the trait “is going to disappear.’’

But some scientists disagree.
“There is no way of predicting any species’s fitness in the absence of environmental settings, because species do not behave as predicted by models,’’ Paulo Petry, a freshwater fish specialist in Latin America for the Nature Conservancy, said.
“I would opt for the precautionary principle and not allow the commercialization of these things in regions where there is even a remote chance of establishing a viable population,” he said.

GM fish are not allowed in Canada and much of Europe, and GloFish cannot be sold in California.
The FDA determined in 2003 that GloFish did not need to go through a full approval process, saying there was no evidence that the altered fish posed an increased risk to the environment and there was an absence of a clear risk to public health.
(Florida, which hosts a large ornamental fish industry, including the two fish farms that raise GloFish, requires approval before genetically modified fish can be raised there.)

“We think the feds should step in whether or not [GloFish] pose a threat. It shows the big holes in our regulatory system, in how we deal with genetically engineered animals,’’ said Eric Hoffman, food and technology campaigner at Friends of the Earth.
“If people look down into water and look at glowing fish, they might be pretty, but it’s a sign of genetic contamination and a type of pollution we don’t want,’’ Hoffman said.