Changes in the Greenland Ice Sheet

Using 14.3 million measurements collected by ESA’s CryoSat mission between January 2011 and January 2014, researchers from the Alfred Wegener Institute in Germany have discovered that the Greenland ice sheet is shrinking in volume by 375 cubic kilometers a year. The study, which was published in a paper published on 20 August 2014 in the European Geosciences Union’s Cryospherejournal, also showed that Antarctica is losing about 125 cubic kilometers a year. Read full article.

Image credit: Helm et al., The Cryosphere, 2014

Note: For more information, see Greenland Ice-Sheet Height.

Antarctic Ice Loss Measurements

Three years of measurements from CryoSat show that the Antarctic Ice Sheet is now losing 159 billion tonnes of ice each year, enough to raise global sea levels by 0.45 mm per year. Read full article.

Image credit: CPOM/Leeds/ESA

The 'Unstable' West Antarctic Ice Sheet: A Primer

Although the Amundsen Sea region is only a fraction of the whole West Antarctic Ice Sheet, the region contains enough ice to raise global sea levels by 4 feet (1.2 meters).

The new finding that the eventual loss of a major section of West Antarctica's ice sheet "appears unstoppable" was not completely unexpected by scientists who study this area. The study, led by glaciologist Eric Rignot at NASA's Jet Propulsion Laboratory, Pasadena, California, and the University of California, Irvine, follows decades of research and theory suggesting the West Antarctic Ice Sheet is inherently vulnerable to change.

Antarctica is so harsh and remote that scientists only began true investigation of its ice sheet in the 1950s. It didn't take long for the verdict on the West Antarctic Ice Sheet to come in. "Unstable," wrote Ohio State University glaciologist John Mercer in 1968. It was identified then and remains today the single largest threat of rapid sea level rise.

Why is West Antarctica's ice sheet considered "unstable"?

The defining characteristic of West Antarctica is that the majority of the ice sheet is "grounded" on a bed that lies below sea level.

In his 1968 paper, Mercer called the West Antarctic Ice Sheet a "uniquely vulnerable and unstable body of ice." Mercer based his statement on geologic evidence that West Antarctica's ice had changed considerably many, many millennia ago at times when the ice sheets of East Antarctica and Greenland had not.

In 1973, University of Maine researcher Terry Hughes asked the question that scientists continue to investigate today. The title of his paper: "Is The West Antarctic Ice Sheet Disintegrating?" In 1981, Hughes published a closer look at the Amundsen Sea region specifically. He called it "the weak underbelly of the West Antarctic ice sheet."

Here's the cause for concern: When the ice sheet is attached to a bed below sea level, ocean currents can deliver warm water to glacier grounding lines, the location where the ice attaches to the bed.

Scientists recognized that this is the first step in a potential chain reaction. Ocean heat eats away at the ice, the grounding line retreats inland and ice shelves lose mass. When ice shelves lose mass, they lose the ability to hold back inland glaciers from their march to the sea, meaning those glaciers can accelerate and thin as a result of the acceleration. This thinning is only conducive to more grounding line retreat, more acceleration and more thinning. In this equation, more ice flows to sea every year and sea level rises.

But that's not all.

Beginning with research flights in the 1960s that made radar measurements over West Antarctica, scientists began to understand that, inland of the ice sheet's edge, the bed slopes downward, precipitously, in some cases.

This downward, inland slope was theorized decades ago, but has been confirmed and mapped in detail in recent years by airborne campaigns such as NASA's Operation IceBridge. In some spots the bed lies more than a mile and a half below sea level. The shape of this slope means that when grounding lines start to retreat, ocean water can infiltrate between the ice and the bed and cause the ice sheet to float off its grounding line.

Why is the Amundsen Sea region more at risk than other parts of West Antarctica?

In addition to the ice sheet being grounded below sea level, there are three main reasons. First, the glaciers here lack very large ice shelves to stem ice flow. Second, they aren't "pinned" by obstructions in their beds except in a few small places, unlike the Ronne and Ross shelves which are pinned down by large islands. Third, as first observed in the 1990s, the area is vulnerable to a regional ocean current, ushered in by the shape of the sea floor and the proximity of the circumpolar deep current. This current delivers warm water to grounding lines and the undersides of ice shelves in the region.

The pace and magnitude of the changes observed in this region match the expectation that Amundsen Sea embayment glaciers should be less stable than others. In some cases, the changes have outstripped expectations.

Pine Island and Thwaites glaciers have experienced significant flow acceleration since the 1970s. Both saw the center of their grounding lines retreat dramatically. From 1992 to 2011, Pine Island's grounding line retreated by 19 miles (31 kilometers) while the center of the Thwaites grounding line retreated by nearly 9 miles (14 kilometers). Annual ice discharge from this region as a whole has increased 77 percent since 1973.

What would a loss of the Amundsen Sea region mean for sea level rise?

Even as Rignot and colleagues suggest that loss of the Amundsen Sea embayment glaciers appears inevitable, it remains extremely difficult to predict exactly how this ice loss will unfold and how long it will take. A conservative estimate is that it could take several centuries.

The region contains enough ice to raise global sea levels by 4 feet (1.2 meters). The most recent U.N. Intergovernmental Panel on Climate Change (IPCC) report estimates that by 2100, sea level will rise somewhere from just less than 1 foot to about 3 feet (26 to 98 centimeters). But the vast majority of these projections do not take into account the possibility of major ice loss in Antarctica. Rignot said this new study suggests sea level rise projections for this century should lean toward the high-end of the IPCC range.

The Amundsen Sea region is only a fraction of the whole West Antarctic Ice Sheet, which if melted completely would raise global sea level by about 16 feet (5 meters).

What are NASA and other science agencies doing to better understand this vulnerable region and its potential impact on global sea level?

To better understand how this section of the ice sheet has changed in recent decades, scientists from NASA and research institutions around the world have made field campaigns to the region and used every airborne and spaceborne tool at their disposal, including NASA satellites and those launched by space agencies in Europe, Japan and Canada.

The National Science Foundation has funded major field campaigns to West Antarctica, including POLENET, which place Global Positioning System (GPS) stations in the area to measure geological changes. A campaign to the Pine Island Glacier ice shelf led by NASA glaciologist Bob Bindschadler measured variables such as water temperature and melting rate at the underside of the ice shelf.

NASA's Operation IceBridge, which began in 2009, continues to fly one extended research campaign over Antarctica each year. IceBridge flights put multiple scientific instruments over key regions of the ice sheet to measure glacier thinning, the shape of the bed and other factors.

In 2017, NASA will launch ICESat-2, the follow-up mission to ICESat, which operated from 2003 to 2009. ICESat-2 will use laser altimetry to make precise measurements of glacier heights. Combined with the ICESat and IceBridge data records, the ICESat-2 measurements will allow for a continuous record of year-over-year change in some of the most remote regions of the world.

Image credit: NASA/GSFC/SVS

Note: For more information, see West Antarctic Glacier Loss Appears Unstoppable.

Pine Island and Thwaites Glaciers, Antarctica

Acquired on 13 April 2014 at 09:03 GMT (11:03 CEST) this image covers parts of Pine Island Glacier and Thwaites Glacier in West Antarctica. This image is among the first from Sentinel-1A, which was launched on 3 April. It was acquired in ‘Interferometric Wide Swath’ mode with a swath width of 250 km and in single polarization. With Pine Island Glacier in a state of irreversible retreat, the Sentinel-1 mission is set to be an excellent tool for monitoring such glaciers as well as for providing timely information on many other aspects of the polar regions, such as sea ice and icebergs.

Image credit: ESA

Antarctica Peninsula

Acquired on 13 April 2014 at 23:57 GMT (14 April at 01:57 CEST) by Sentinel-1A, this image shows a transect over the northern part of the Antarctica Peninsula. It was acquired in the satellite’s ‘strip map’ mode with a swath width of 80 km and in dual polarization. The colors indicate how the land, ice and water reflect the radar signal differently.

Image credit: ESA

Pine Island Glacier Retreat

Pine Island is the largest glacier in the West Antarctic Ice Sheet and one of the fastest ice streams on the continent, flowing into Pine Island Bay in the Amundsen Sea. Ten percent of the West Antarctic Ice Sheet drains out to the sea by way of this glacier. Radar data from the two ERS missions show that from 1992–2011 the glacier thinned by about 200 m, and its grounding line retreated up to 40 km. This animation is based on data from the of the STSE-GreenSAR project.

Video credit: Planetary Visions / University of Edinburgh / University of Leeds / ESA

Ice Sheet Contribution to Sea-Level Rise

This animation merges 20 years of satellite data to demonstrate how much – and how fast – the ice sheets cover Greenland and Antarctica are melting and their contribution to sea-level rise.

Video credit: Planetary Visions

Thinning Antarctic Ice

Three years of measurements from CryoSat show that the West Antarctic Ice Sheet is estimated to be losing over 150 cubic kilometers of ice each year.

Image credit: CPOM/ESA

The Coldest Place on Earth

With remote-sensing satellites, scientists have found the coldest places on Earth, just off a ridge in the East Antarctic Plateau. The coldest of the cold temperatures dropped to minus 135.8 F (minus 93.2 C) -- several degrees colder than the previous record.

What is the coldest place on Earth? It is a high ridge in Antarctica on the East Antarctic Plateau where temperatures in several hollows can dip below minus 133.6 degrees Fahrenheit (minus 92 degrees Celsius) on a clear winter night.

Scientists made the discovery while analyzing the most detailed global surface temperature maps to date, developed with data from remote sensing satellites including the new Landsat 8, a joint project of NASA and the U.S. Geological Survey (USGS). Ted Scambos, lead scientist at the National Snow and Ice Data Center in Boulder, Colorado, joined a team of researchers reporting the findings Monday at the American Geophysical Union meeting in San Francisco.

Researchers analyzed 32 years' worth of data from several satellite instruments. They found temperatures plummeted to record lows dozens of times in clusters of pockets near a high ridge between Dome Argus and Dome Fuji, two summits on the ice sheet known as the East Antarctic Plateau. The new record of minus 136 F (minus 93.2 C) was set August 10, 2010.

That is several degrees colder than the previous low of minus 128.6 F (minus 89.2 C), set in 1983 at the Russian Vostok Research Station in East Antarctica. The coldest permanently inhabited place on Earth is northeastern Siberia, where temperatures in the towns of Verkhoyansk and Oimekon dropped to a bone-chilling 90 degrees below zero Fahrenheit (minus 67.8 C) in 1892 and 1933, respectively.

"We had a suspicion this Antarctic ridge was likely to be extremely cold, and colder than Vostok because it's higher up the hill," Scambos said. "With the launch of Landsat 8, we finally had a sensor capable of really investigating this area in more detail."

The quest to find out just how cold it can get on Earth -- and why -- started when the researchers were studying large snow dunes, sculpted and polished by the wind, on the East Antarctic Plateau. When the scientists looked closer, they noticed cracks in the snow surface between the dunes, possibly created when wintertime temperatures got so low the top snow layer shrunk. This led scientists to wonder what the temperature range was, and prompted them to hunt for the coldest places using data from two types of satellite sensors.

They turned to the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on NASA's Terra and Aqua satellites and the Advanced Very High Resolution Radiometer (AVHRR) on several National Oceanic and Atmospheric Administration satellites. These sensitive instruments can pick up thermal radiation emitted from Earth's surface, even in areas lacking much heat.

Using these sensors to scan the East Antarctic Plateau, Scambos detected extremely cold temperatures on a 620-mile stretch of the ridge at high elevations between Argus and Fuji, and even colder temperatures lower elevations in pockets off the ridge. Then, with the higher resolution of the Thermal Infrared Sensor (TIRS) aboard Landsat 8, the research team pinpointed the record-setting pockets.

The team compared the sites to topographic maps to explore how it gets so cold. Already cold temperatures fall rapidly when the sky clears. If clear skies persist for a few days, the ground chills as it radiates its remaining heat into space. This creates a layer of super-chilled air above the surface of the snow and ice. This layer of air is denser than the relatively warmer air above it, which causes it to slide down the shallow slope of domes on the Antarctic plateau. As it flows into the pockets, it can be trapped, and the cooling continues.

"By causing the air to be stationary for extended periods, while continuing to radiate more heat away into space, you get the absolute lowest temperatures we're able to find," Scambos said. "We suspected that we would be looking for one magical site that got extremely cold, but what we found was a large strip of Antarctica at high altitude that regularly reached these record low temperatures."

The study is an example of some of the intriguing science possible with Landsat 8 and the TIRS instrument, which was built at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Since its launch February 11, Landsat 8 has captured approximately 550 scenes per day of Earth's land surface. USGS processes, archives and distributes the images free of charge over the Internet.

"With Landsat 8, we expect to see more accurate and more detailed maps of the landscape than we've ever been able to see," said James Irons, the mission's project scientist at Goddard. "If change is occurring, I think we'll be able to detect it earlier and track it."

Researchers also are eager to see what new results come out of Landsat 8, both from icy plateaus and Earth's warmer regions.

"What we've got orbiting Earth right now is a very accurate and consistent sensor that can tell us all kinds of things about how the land surface of Earth is changing, how climate change is impacting the surface of Earth, the oceans of Earth, and the icy areas of Earth," Scambos said. "Finding the coldest areas on Earth is just the beginning of the discoveries we're going to be able to make with Landsat 8."

Image credit: Ted Scambos, National Snow and Ice Data Center; text credit: NASA

Totten Glacier Ice Shelf

This image shows the Totten Glacier ice shelf in East Antarctica (the wrinkled white area at top left) on September 25, 2013. Two large open-water polynyas appear on the sea ice below and to the right of the shelf, as well as several smaller ones. The open-water areas are bright black. The stippled diagonal line from lower left to upper right is the outer edge of the sea ice, with cloud cover to the right of that line. The image is from the Moderate Resolution Imaging Spectroradiometer instrument on NASA's Aqua satellite.

Photo credit: NASA

Note: For more information, see NASA Finds Reducing Salt Is Bad for Glacial Health.

Pine Island Glacier Iceberg by Proba-2

The smallest camera on one of ESA’s smallest satellites caught this image of a giant iceberg – larger than Singapore – drifting away from Antarctica’s Pine Island Glacier.

The espresso cup-sized Exploration Camera, X-Cam, on ESA’s Proba-2 satellite took this picture on 19 November, peering eastwards into the Antarctic interior.

The 700 sq km iceberg in open water to the right side of the image, officially known as iceberg B-31, broke away from the Pine Island Glacier on the Antarctic west coast back in July. Such a ‘calving’ was widely anticipated, with a crack in the ice having formed over several years.

The berg is gradually drifting away from its parent glacier, expected either to move east, parallel to the coast, or head out into the Southern Ocean.

Proba-2’s X-Cam’s black and white image gives a wider perspective than a standard Earth observation camera, more like an astronaut’s eye view, but it was taken at around double the altitude that human crews currently fly, at more than 700 km.

Less than a cubic meter in size, Proba-2 focuses on observing solar activity and space weather. But it also keeps a small eye on its home world.

One of the 17 experimental technologies hosted on Proba-2 is the compact X-Cam. Housed on the underside of the satellite, the monochrome X-Cam observes in the visible and infrared with a 100° field of view.

Photo credit: ESA

Note: For more information, see PIA17694: Pine Island Glacier, Antarctica, MISR Multi-angle Composite.

Rates of Basal Melt of Antarctic Ice Shelves

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

Note: For more information, see Warm Ocean Causing Most Antarctic Ice Shelf Mass Loss

SMOS Reveals Thin Sea Ice

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Sea-ice thickness measured by SMOS in the Arctic and Antarctic. Arctic sea ice is significantly thinner in February 2012 than in February 2011. This year, the Arctic experienced a record low of sea-ice extent since satellite measurements began in the 1970s.

Video credit: Planetary Visions

Antarctic Ozone Holes: 2011 and 2012

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Ozone distribution over the South Pole from July to December during the years 2011 (left) and 2012 (right).

The 2012 ozone hole duration, geographical extension and depth was much smaller than that of 2011. Ozone loss over the South Pole is displayed at the bottom (the bold dark line indicates the ozone loss for 2012 and the grey line for 2011). The ozone maps were generated by the assimilation of GOME-2 total ozone data into the model TM3DAM. GOME-2 is carried by Eumetsat’s MetOp mission.

Video credit: KNMI

Concordia Base, Antarctica

The Proba-1 microsatellite's High Resolution Camera images the French-Italian Concordia base in the Antarctic interior. The image has 5-m spatial resolution and covers approximately 25 sq km. It was acquired on 24 November 2012.

Photo credit: ESA

A Crack on Pine Island Glacier

This Envisat image shows the Pine Island Glacier in West Antarctica and reveals a crack in the glacier’s tongue about 25 km long. The image was acquired by Envisat’s radar on 6 April 2012, just two days before contact with the satellite was lost.

Photo credit: ESA

Larsen B: 2002-2012

This animation shows radar images from the Envisat satellite from 2002 to 2012 of the Larsen B ice shelf in Antarctica. Over the last decade, the ice shelf has disintegrated by 1790 sq km.

Photo credit: ESA