Warm ocean causing most Antarctic Ice shelf mass loss

Rates of basal melt of Antarctic ice shelves (melting of the shelves from underneath) overlaid on a 2009 mosaic of Antarctica created from data from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard NASA's Terra and Aqua spacecraft.

Red shades denote melt rates of less than 5 meters (16.4 feet) per year (freezing conditions), while blue shades represent melt rates of greater than 5 meters (16.4 feet) per year (melting conditions).

The perimeters of the ice shelves in 2007-2008, excluding ice rises and ice islands, are shown by thin black lines.

Each circular graph is proportional in area to the total ice mass loss measured from each ice shelf, in gigatons per year, with the proportion of ice lost due to the calving of icebergs denoted by hatched lines and the proportion due to basal melting denoted in black.

Image credit: NASA/JPL-Caltech/UC Irvine/Columbia University 

From NASA

Ocean waters melting the undersides of Antarctic ice shelves are responsible for most of the continent's ice shelf mass loss, a new study by NASA and university researchers has found.

Scientists have studied the rates of basal melt, or the melting of the ice shelves from underneath, of individual ice shelves, the floating extensions of glaciers that empty into the sea.
But this is the first comprehensive survey of all Antarctic ice shelves.
The study found basal melt accounted for 55 percent of all Antarctic ice shelf mass loss from 2003 to 2008, an amount much higher than previously thought.

 Pine Island Bay and Amundsen Sea (NGA charts)

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Antarctica holds about 60 percent of the planet's fresh water locked into its massive ice sheet.
Ice shelves buttress the glaciers behind them, modulating the speed at which these rivers of ice flow into the ocean.
Determining how ice shelves melt will help scientists improve projections of how the Antarctic ice sheet will respond to a warming ocean and contribute to sea level rise.
It also will improve global models of ocean circulation by providing a better estimate of the amount of fresh water ice shelf melting adds to Antarctic coastal waters.

The study uses reconstructions of ice accumulation, satellite and aircraft readings of ice thickness, and changes in elevation and ice velocity to determine how fast ice shelves melt and compare the mass lost with the amount released by the calving, or splitting, of icebergs.

 Calving front of an ice shelf in West Antarctica.
The traditional view on ice shelves, the floating extensions of seaward glaciers, has been that they mostly lose ice by shedding icebergs.
Image credit: NASA/GSFC/Jefferson Beck

"The traditional view on Antarctic mass loss is it is almost entirely controlled by iceberg calving," said Eric Rignot of NASA's Jet Propulsion Laboratory in Pasadena, Calif., and the University of California, Irvine.
Rignot is lead author of the study to be published in the June 14 issue of the journal Science.
"Our study shows melting from below by the ocean waters is larger, and this should change our perspective on the evolution of the ice sheet in a warming climate."

Ice shelves grow through a combination of land ice flowing to the sea and snow accumulating on their surface.
To determine how much ice and snowfall enters a specific ice shelf and how much makes it to an iceberg, where it may split off, the research team used a regional climate model for snow accumulation and combined the results with ice velocity data from satellites, ice shelf thickness measurements from NASA's Operation IceBridge -- a continuing aerial survey of Earth's poles -- and a new map of Antarctica's bedrock.
Using this information, Rignot and colleagues were able to deduce whether the ice shelf was losing mass through basal melting or gaining it through the basal freezing of seawater.

 This photo shows the ice front of the ice shelf in front of Pine Island Glacier, a major glacier system of West Antarctica.

The image was taken during the NASA/Centro de Estudios Cientificos, Chile (CECS) Antarctic campaign of Fall 2002.

Image credit: NASA/JPL-Caltech/UC Irvine

In some places, basal melt exceeds iceberg calving.
In other places, the opposite is true.
But in total, Antarctic ice shelves lost 2,921 trillion pounds (1,325 trillion kilograms) of ice per year in 2003 to 2008 through basal melt, while iceberg formation accounted for 2,400 trillion pounds (1,089 trillion kilograms) of mass loss each year.

Basal melt can have a greater impact on ocean circulation than glacier calving.
Icebergs slowly release melt water as they drift away from the continent.
But strong melting near deep grounding lines, where glaciers lose their grip on the seafloor and start floating as ice shelves, discharges large quantities of fresher, lighter water near the Antarctic coastline.
This lower-density water does not mix and sink as readily as colder, saltier water, and may be changing the rate of bottom water renewal.

This photo shows the ice front of Venable Ice Shelf, West Antarctica, in October 2008.

Image credit: NASA/JPL-Caltech/UC Irvine

"Changes in basal melting are helping to change the properties of Antarctic bottom water, which is one component of the ocean's overturning circulation," said author Stan Jacobs, an oceanographer at Columbia University's Lamont-Doherty Earth Observatory in Palisades, N.Y.
"In some areas it also impacts ecosystems by driving coastal upwelling, which brings up micronutrients like iron that fuel persistent plankton blooms in the summer."

 Filchner-Ronne Ice shelf (NGA charts)

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The study found basal melting is distributed unevenly around the continent.
The three giant ice shelves of Ross, Filchner and Ronne, which make up two-thirds of the total Antarctic ice shelf area, accounted for only 15 percent of basal melting.
Meanwhile, fewer than a dozen small ice shelves floating on "warm" waters (seawater only a few degrees above the freezing point) produced half of the total melt water during the same period.
The scientists detected a similar high rate of basal melting under six small ice shelves along East Antarctica, a region not as well known because of a scarcity of measurements.

The researchers also compared the rates at which the ice shelves are shedding ice to the speed at which the continent itself is losing mass and found that, on average, ice shelves lost mass twice as fast as the Antarctic ice sheet did during the study period.

"Ice shelf melt doesn't necessarily mean an ice shelf is decaying; it can be compensated by the ice flow from the continent," Rignot said.
"But in a number of places around Antarctica, ice shelves are melting too fast, and a consequence of that is glaciers and the entire continent are changing as well."

Links :

• Nature : Oceans melt Antarctica's ice from below

Antarctic's mountains revealed by sharpest map yet

 The bedrock beneath Antarctica.

Our understanding of what lies beneath the world's biggest ice sheet has taken another leap forward. This video strips away Antarctic ice to reveal a new, and much more detailed map of the bedrock below.
This map, called Bedmap2, was compiled by the British Antarctic Survey and
incorporates millions of new measurements, including substantial data sets from NASA's ICES at satellite and an airborne mission called Operation IceBridge.
Credit: NASA's Goddard Space Flight Center

From NationalGeographic

Buried under miles of ice, Antarctica's mysterious mountain ranges are coming into sharper focus thanks to a new map.

Created by the British Antarctic Survey, Bedmap2 drew upon millions of new measurements of the frozen continent's surface elevation, ice thickness, and bedrock topography from a wide variety of sources collected over several decades.

Due to technological advances, Bedmap2 is also higher in resolution, more precise, and covers more of the continent than the original Bedmap, produced more than ten years ago, according to Charles Webb, deputy program scientist for cryospheric sciences at NASA headquarters. Earth's frozen regions are collectively called the cryosphere.

For example, the original Bedmap relied mostly on ground-based measurements, which limited the scientists in terms of how much land they could cover, Webb noted.

But a NASA program called Operation IceBridge sends out airplanes that fly over the entire continent.
The airplanes are equipped with lasers that measure the surface mountains' heights and other features, as well as ice-penetrating radar that maps subglacial bedrock—"giving [scientists] a more 3-D picture of the ice sheet itself," Webb said.

These images depict the differences between Antarctica's ice sheet with its underlying topography.

(Vertical scale has been magnified by a factor of 17 to make terrain features such as mountains and valleys more visible.)

In addition, the new data has revealed several smaller features—both on Antarctica's surface and buried under the ice—that were missed in the previous Bedmap effort.
(Also see "First Detailed Pictures: Antarctica's 'Ghost Mountains.'")

To Webb, "the piece that's exciting is that the increased resolution ... gives us better insight into what drives the flow of the ice."

For instance, scientists want to know the shapes of mountains and rocks to model how fast ice will move across these features on its way to the ocean, where the ice can melt and contribute to sea level rise, he said.

Overall, loss of polar ice has contributed about 11.1 millimeters (0.03 feet) to global sea levels since 1992, research shows. Sea levels are currently rising at a rate of 3.2 millimeters a year.

Links : 

• NASA :  NASA's IceBridge Mission Contributes to New Map of Antarctica
• GeoGarage blog : Antarctic's hidden world revealed

A breakthrough in how we work to protect our oceans

The wild and beautiful Bering Sea

From Huffington Post

The Bering Sea is known to scientists and conservationists as one of the most remarkable places on Earth -- a home to sponges, coral, fish, crab, skates, sperm whales, orcas, Stellar sea lions, and a vast array of other species all part of a delicate ecosystem extremely vulnerable to human activity.

But here's what's new -- as of this week, the Bering Sea is remarkable for another reason -- it's the impetus for a an amazing breakthrough in the way we work to protect our oceans.

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On Monday in Juneau, Alaska, the North Pacific Fishery Management Council voted to identify key coral areas in the Bering Sea canyons and consider measures to protect them.
While this may sound like a routine decision in a far off place, it's anything but the status quo.

The council's decision comes in the middle of an ongoing campaign to protect the "Grand Canyons of the Sea" from the pollock industry that uses destructive fishing gear like bottom trawlers that destroy fragile corals and threaten life in the Bering Sea.
You may not have heard much about pollock day-to-day, but it's in fish sticks, fast food fish sandwiches, and even imitation crab.
It's a big deal fish -- in fact, some people even call it the "billion dollar fish" because of how much the industry depends on it.

This campaign, like most conservations initiatives, has gathered together numerous green groups like Greenpeace, the World Wildlife Fund, and Mission Blue.
But what's different about this campaign is that major seafood retailers like Safeway, Trader Joe's, and, yes, even McDonald's have looked beyond their next quarters' earnings to the long-term viability of our environment (and their products)
These business leaders have admirably urged the Council to look further into the available science to protect the canyons from destructive fishing, because they too want the Bering Sea to have a sustainable foundation for the future.
We know from what we've seen from the oceans around the world that a thriving ecosystem today can turn into a wasteland tomorrow without sustainable management, so the problem is urgent.

What else is new with this campaign is the truly remarkable amount of citizen engagement.
This week, as the Council deliberated in Juneau, everywhere they went flyers, posters, and banners held by activists reminded them that more than 100,000 people were urging them to protect the canyons -- an unprecedented amount of public input in this process.
When Council member John Henderschedt spoke to his breakthrough motion yesterday he began by saying, "thanks to all who provided comments -- your voices are important to this process, and they have been heard."

If the industry and government operated in secret, who knows what it would take for them to work sustainably.
But because Greenpeace and other conservation groups have been able to show the wider world what's at stake in the Bering Sea, people have been able to decide for themselves how they want their world.
Greenpeace has had the privilege of taking this message to the decision-makers in government and industry to create a new way forward, one that includes more voices than just that of the highest bidder.

The struggle to protect the "Grand Canyons of the Sea" is far from over, but on Monday in Juneau something remarkable happened, something that might just signal a sea change in how we protect our oceans.

Links :

• Greenpeace : Protect the Bering Sea
• National Geographic : Sylvia Earle’s 19th “Hope Spot” named in Bering Sea canyons
• Alaska Public : Fisheries regulators take steps toward conservation of Bering Sea canyons

World's most dangerous oceans for shipping identified

This WWF infographic shows the number of accidents at sea in the world's most dangerous waters.

From Ibtimes 

A new study commissioned by the World Wildlife Fund for World Oceans Day, pinpoints the planet’s most dangerous oceans and describes how shipwrecks are likely to increase in the coming years because of expanding fleets and a warming climate.

Scientists at Southampton Solent University, who carried out the research for WWF, said that while the number of accidents at sea has fallen by about 18 percent since 1980, many incidents occur in areas of environmental significance, such as the South China Sea and East Indies, eastern Mediterranean, North Sea, Black Sea and British Isles.

The sea areas where ships continue to be lost are also waters of environmental significance

The North Sea is one of the most intensively sailed seas in the world, with more than 120,000 ship movements each year, according to Simon Walmsley, marine manager at WWF.

“Shipping lanes around the U.K. are already some of the world’s busiest and will get busier as the global fleet expands,” he noted.

“The risk of accidents and environmental disaster is only going to increase, so efforts must be made to lower the risk.”

A container ship sails past barges during foggy conditions at Hong Kong's Victoria Harbour March 15, 2010.
photo Bobby Yup, Reuters

Over in the South China Sea and East Indies, the world’s top accident area, concerns are even greater. “Since 1999, there have been 293 shipping accidents in the South China Sea and East Indies, home of the Coral Triangle and 76 percent of the world’s coral species,” Walmsley said.

“As recently as April of this year, we’ve seen a Chinese fishing boat run aground on a protected coral reef in the Philippines that had already been damaged by a U.S. Navy ship in January.”

The number of ships sailing the open oceans has increased dramatically over the past 15 years to about 105,000 from roughly 85,000.

According to the WWF report, fishing vessels account for nearly one-quarter of the vessels lost at sea, while general cargo ships make up more than 40 percent. Cargo ships tend to operate on short shipping routes associated with tramp trading “where ships don’t have a set route and pick up opportunistic trade, particularly in Southeast Asia,” the report said.

Walmsley noted that in the past we’ve seen reviews of safety and environment measures only after major accidents.

“That needs to change if we want to maintain healthy seas,” he said.

Oil spill from sunken tanker Prestige on the Galician Costa de la Muerte near Camelle, Spain.
© WWF / Raúl Garcia

The scale of an environmental risk can be affected by the type of cargo onboard, such as oil and other hazardous substances, and the sensitivity of the marine area where the accident occurs.

Walmsley pointed to the 2002 sinking of the Prestige oil tanker, when more than 70,000 tons of oil was released into the Atlantic Ocean off the Spanish coast, as one prominent recent example.
“The Prestige oil spill caused not only environmental impacts but economic losses estimated at €8 billion [$10.4 billion],” he said.

“Even small-scale accidents in very sensitive environments, like the Great Barrier Reef, can have profound environmental consequences.”

The study expressed concerns about new ports under construction near the Great Barrier Reef that would be used in the transport of coal from Australia but also boost traffic in the area, thus increasing risks.

A recent National Geographic article called Australia “the face of climate change to come,” and the WWF report noted that increased storm surges, changing wind and wave patterns, and extreme weather events will all exacerbate the risks of foundering, leading to potentially catastrophic environmental destruction.

According to the scientists at Southampton Solent University, some 50 percent of all accidents are caused by foundering, where a boat sinks in rough weather, leaks or breaks in two.

They warn of a high probability of more accidents unless precautionary measures are put in place to address the increasing risk factors.

Petrol tanker waiting for its cargo, Fujeirah port, United Arab Emirats, Indian Ocean
© © Michel Gunther / WWF-Canon

“We really want to see the shipping industry promote greater owner and operator responsibility and encourage owners to register with better flag states, the country which a vessel is registered to,” Walmsley said

 “Additionally, irresponsible and badly performing owners and countries need to be exposed in order to motivate them to significantly increase their standards, which will decrease the number of accidents we see still occurring today.”

 The Rena, grounded on the Astrolabe reef 14 miles from Tauranga Harbour on New Zealand’s North Island, got stuck during bad weather and rough seas in October 2011. (AP)

A separate study, released this year by Allianz Global Corporate and Specialty Insurance, pointed to a different area of shipping as the biggest concern: human error.
In its annual “Safety and Shipping Review,” Allianz researchers cited the largest accidents in 2012 -- the Costa Concordia off the coast of Italy, the MV Rena off the coast of New Zealand and the Rabaul Queen off Papua New Guinea -- as evidence supporting their theory.

“For some commercial ship owners, especially in the hard-pressed bulk cargo and tanker sectors, there is little money for maintenance and little money for training,” Sven Gerhard, Allianz's global marine head of hull and marine liabilities, explained.

He said the Maritime Labor Convention of 2006, which comes into force later in 2013, would help improve safety by improving the working conditions of seafarers.

Links :

• WWF : Accidents at sea report summary / 15 years of shipping accidents
• Discovery News :  World's most dangerous oceans identified

US NOAA update in the Marine GeoGarage

18640 San Franciso to Punto Arena

14 charts have been updated in the Marine GeoGarage

(NOAA update mi-May 2013-1st week of June 2013)

NOAA Charts Show New IMO Traffic Separation Scheme off California
NOAA has updated a series of raster and electronic navigational charts to comply with routing regulations approved late last year by the International Maritime Organization (IMO COLREG.2/Circ.64,December 4, 2012).
The routing establishes a new traffic separation scheme off the northern coast of California, effective June 1

see GeoGarage blog : California shipping lanes moved in attempt to avoid killing whales

• 11324 Galveston Bay Entrance Galveston and Texas City Harbors
• 11356 Isles Dernieres to Point au Fer
• 11428 Okeechobee Waterway St. Lucie Inlet to Fort Myers; Lake Okeechobee
• 11542 Florida Keys Sombrero Key to Sand Key
• 12326 Approaches to New York Fire lsland Light to Sea Girt
• 12332 Raritan River Raritan Bay to New Brunswick
• 12368 North Shore of Long Island Sound Sherwood Point to Stamford Harbor
• 13223 Narragansett Bay. Including Newport Harbor
• 13287 Saco Bay and Vicinity
• 13298 Kennebec River Bath to Courthouse Point
• 18649 Entrance to San Francisco Bay
• 18724 Port Hueneme And Approaches;Port Hueneme
• 18725 Port Hueneme to Santa Barbara;Santa Barbara;Channel Islands Harbor and Port Hueneme;Ventura
• 18746 San Pedro Channel;Dana Point Harbor

Today 1024 NOAA raster charts (2166 including sub-charts) are included in the Marine GeoGarage viewer.


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See the changes in new chart editions.
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Note : NOAA updates their nautical charts with corrections published in:

• U.S. Coast Guard Local Notices to Mariners (LNMs),
• National Geospatial-Intelligence Agency Notices to Mariners (NMs), and
• Canadian Coast Guard Notices to Mariners (CNMs)

While information provided by this Web site is intended to provide updated nautical charts, it must not be used as a substitute for the United States Coast Guard, National Geospatial-Intelligence Agency, or Canadian Coast Guard Notice to Mariner publications

Please visit the NOAA's chart update service for more info.

 

 

1849 Imray nautical map of California Coast

"This wa probably the best chart of the West Coast avaolable in 1849"

see Geographicus