Icebridge : Scientists Map Thinning Ice Sheets in Antarctica

Blog Feature: Ice Bridge

Climate change has weakened the ice sheets of western Antarctica. Scientists from Lamont-Doherty are flying over the region on a NASA-led mission called Ice Bridge to understand what's happening on and below the ice. What they find may help predict future sea level rise.


Posted By: Margie Turrin on November 14, 2016
Along the edge of the Antarctic Peninsula. (photo M. Turrin)

Along the edge of the Antarctic Peninsula, large chunks of ice flow freely from the land into the ocean. Photo: M. Turrin

Ice shelves can behave like dominos. When they are lined up and the first one collapses it can cause a rippling effect like dominos. We have seen this with the Larsen ice shelves. Named in series, the Larsen A, B and C shelves extended along the northeastern edge of the West Antarctic Peninsula, and covered a large swath of coastline as recently as 20 years ago. Bordering the western edge of the Weddell Sea, each extended from a separate embayment yet merged into a large expanse of ice, considered one ice shelf complex. All this was before 1995, before the dominoes began to collapse.

Glacier on the Antarctic Peninsula moving. (Photo M. Turrin)

In this area of the Antarctic Peninsula, ice moves as if it is on a conveyor belt, flowing down between the mountain peaks and toward the ocean. You can see here it is building an ice moraine as it flows. This stretch of glaciers flows onto the Larsen catchment. Photo: M. Turrin

It was January 1995, toward the end of the austral summer, when Larsen A, the smallest of the three shelves, broke apart rather suddenly and was gone. The furthest north of the Larsen trio, this small shelf was situated just north of the Larsen B and just outside of the Antarctic Circle. Due to its size and location, the 1,500-square-kilometer block of ice was the most vulnerable of the three Larsen shelves. Warming water that had been moving around the peninsula was the probable cause for the demise.

The Larsen ice shelf complex, as it was and what it is now. (Images from NASA, compilation from Carbon Copy)

The Larsen ice shelf complex. Images: NASA; compilation: Carbon Copy

When Larsen A disappeared, Larsen B immediately became more vulnerable. Although twice the size at 3,250 square kilometers, the shelf was now un-buffered from warming ocean waters to the north; this combined with several warm summers and Larsen B weakened and became destabilized. In 1998, satellites captured evidence of the front edge of Larsen B beginning to change. Satellite images pointed out melt water ponds on the surface of the shelf, but with some 220 meters of ice thickness, these ponds did not seem to pose a threat. Then between early February and early March 2002, the shelf suffered a massive collapse, with section after section all but evaporating before our eyes. There was disbelief among the science community that a section of shelf this size, and one that had been relatively stable for an estimated 10,000-12,000 years, could so swiftly suffer a collapse. The second domino had fallen.

The Antarctic Peninsula has elevation rising 8000 ft. with ice covering the tops of the mountains in thick layers. (Photo M. Turrin)

The Antarctic Peninsula has elevation rising 8,000 ft., with ice covering the tops of the mountains in thick layers. Photo: M. Turrin

With the loss of a significant section of the Larsen shelf complex, there was a subsequent acceleration of the glaciers that had once been braced by the shelves’ protective presence. Without the stable pressure pushing back against these glaciers, the ice sheet in this area accelerated by up to 300 percent, transferring ice from the Antarctic continent into the ocean and contributing more ice to sea level rise. With the acceleration came a rapid loss in size in the glaciers feeding the Larsen area.

Larsen C and the crack that has developed mapped through time. (Modis imagery annotated by the MIDAS project.)

Larsen C and the crack that has developed, mapped through time. Image: Modis imagery annotated by the MIDAS project

Larsen C remains the fourth largest of the ice shelves by a few hundred square kilometers of ice. A crack appeared in the shelf in 2011 and has grown in size over the subsequent years. Set back about 20 kms. from the edge of the shelf, it threatens to break off about 8 percent of the shelf, or a chunk of ice about the same size as the state of Delaware, at ~6,000 sq. km. With the crack set so far back, there is concern that it might threaten the integrity of the larger ice sheet, weakening the support that holds the shelf in place.

Crack in the Larsen C Ice Shelf that continues to spread, even in the winter months. (Photo M. Turrin)

Crack in the Larsen C Ice Shelf that continues to spread, even in the winter months. Photo: M. Turrin

Just as Larsen B revealed the speed with which an ice shelf can collapse, Larsen C may be poised to reveal how quickly a large crack can propagate along the shelf. The rift is growing even during the Antarctic winter, adding an additional 22 kms. to a length of 130 kms. in total during the last austral winter between March and August 2016. In addition, the crack has widened from 200 meters to 350 meters. Overflying the crack, we were able to collect high resolution imagery that will help with tracking the fate of the third domino in the lineup.

Section of the deep crack in the Larsen C ice shelf. (Digital Mapping System from the IceBridge Project.)

A section of the deep crack in the Larsen C ice shelf collected by high resolution imagery using the Digital Mapping System as part of the IceBridge Project. Photo: DMS team, IceBridge

IceBridge: Since 2009, the NASA IceBridge project has brought together science teams to monitor and measure each of the ice features in order to improve our understanding of changes in the climate system and our models. Lamont-Doherty, under lead scientists Jim Cochran and Kirsty Tinto, has led up the gravity and magnetics measurements for these campaigns.


Posted By: Margie Turrin on November 10, 2016
Pine Island Ice Shelf

As we fly over Pine Island Glacier, West Antarctica the blowing snow adds a surreal quality to the 200 ft. high towering edge of the ice shelf. (Photo M. Turrin)

If you have studied the impacts of climate on Antarctica you have encountered Pine Island Glacier. Tucked in at an angle under the West Antarctic Peninsula handle, this seemingly innocuous glacier has been making headlines for years as one of the fastest flowing ice stream glaciers on Earth. In Antarctica, Pine Island pushes ice at a rapid clip into Pine Island Bay part of the larger Amundsen Sea. So although we have never met face to face, Pine Island is a glacier I have known for years.

Antarctica has two large ice sheets, sensibly labeled the West Antarctic Ice Sheet and the East Antarctica Ice Sheet and separated by the looming Transantarctic Mountains that break through above the thick layer of ice covering much of Antarctic’s surface. In large part West Antarctica is comprised of the Antarctic Peninsula, the handle shaped extension of the continent reaching out towards South America, but below that there is a vulnerable area that drains into Amundsen Sea, one of three catchment areas for this ice sheet. Glaciers in this region have been changing rapidly, led by Pine Island and the neighboring Thwaites. If melted, the ice from Pine Island and Thwaites glaciers together, has the capacity to raise global sea level by up to 2 meters (~7 feet.)

velocity map

The red color represents the fast moving ice of Pine Island glacier in this velocity map on the left. On the left side is a map of subglacial topography showing in dark blue the deep trough that underlies the glacier. (credit velocity map E. Rignot)

For Pine Island the vulnerability results from a compounding of challenges, a small ice shelf offering little support to the land ice behind and little protection from the warming ocean water that makes its way up onto the shelf. In addition the base of the glacier rests on land that is backward sloping, or tipping back underneath the ice. A retrograde bed, as these are called, allows the warm ocean water access to move back under the glacier, further destabilizing and acceleration ice flow.

Crevassing in the ice shows areas where there is strain from ice flowing at different rates. Ice will often crevasse as it accelerates. (Photo M. Turrin)

Crevassing, or deep cuts in the ice, shows areas where there is strain from ice flowing at different rates. Ice will often crevasse as it accelerates, as is shown in this heavily crevassed ice flowing out from the Pine Island ice shelf.  (Photo M. Turrin)

At 160 miles of length, and 68,000 square miles of catchment, Pine Island handles the drainage for approximately one tenth of the West Antarctic Ice Sheet. Over the last forty years it has been over-performing, accelerating its flow, and is attributed with one quarter of Antarctica’s current ice loss. In its years of operation (2003-2010), Ice Sat I satellite  provided us with a series of measurements for this glacier showing that Pine Island Glacier was moving more ice into the ocean than any other drainage basin worldwide. Since 2009 the IceBridge project has continued this monitoring, extending our data for this region so that we won’t miss critical information while IceSat II is being prepared for a 2018 launch. Pine Island glacier measurements are critically important to help us project global sea level rise.

On the DC8

On board the DC8 there is a flight command center with a very busy team that works between the science team and the air crew to ensure the science is completed safely and as designed. (photo M. Turrin)

Pine Island glacier is shrinking. As the glacier has accelerated its flow, the ice stream has thinned and correspondingly the face of the glacier has lost elevation. In some areas ice elevation loss has equaled 4 meters or more a year. The drop in elevation is more  quadruple the annual precipitation for the area, and has occurred in both summer and winter.


Ice Bridge laser image of the crack in Pine Island Glacier. The deep blue line bisecting the front of the glacier is the crack or crevasse in the ice. The depth of the crack that cuts in from the edge of the ice shelf is close to 40 meters deep in this area. (image NASA IceBridge)

More bad news may be ahead for Pine Island. Although the glacier does not have a large ice shelf, there is a relatively small shelf that helps to restrain some of the flow from land to ocean. However, in the last decade a fairly significant crack has developed in the shelf threatening to pull off another large chunk of ice and relaxing the hold the shelf has on the ice behind. As we overflew two locations IceBridge surface laser measurements captured the crack depth at 60 and 70 meters deep. This crack has continued to expand over the last few years and it is only a matter of time before this section of shelf will separate moving off into the ocean and leaving the ice shelf more exposed.

The Pine Island Glacier crack extending back into the glacier. (Photo M. Turrin)

The Pine Island Glacier crack extending back into the glacier. (Photo M. Turrin)

IceBridge: Since 2009, the NASA IceBridge project has brought together science teams to monitor and measure each of the ice features in order to improve our understanding of changes in the climate system and our models. Lamont-Doherty, under lead scientists Jim Cochran and Kirsty Tinto, has led up the gravity and magnetics measurements for these campaigns.

Posted By: Margie Turrin on November 06, 2016
Grease Ice

Newly formed sea ice called “grease ice” looks like thin layers of mica along the front of the Getz Ice Shelf, Antarctica. Photo: M. Turrin

Antarctic ice appears in a range of types and sizes, from the newly formed skim of ice on the ocean called grease ice (above), to the older meter thick layers of sea ice, to chunks of icebergs, floating reaches of ice shelves, and finally the massive land based Antarctic ice sheet. Each part of this ice inventory has a unique role in the larger climate system, but they also work together. As part of this year’s IceBridge Antarctic flight campaign, we are focused largely on the coastline to build a better understanding of the interaction of these different pieces in the ice system. This understanding is central to improving our climate models.

Break in Ice Shelf

Evidence of a break along the front edge of Getz Ice Shelf, Antartica. In the foreground a mixture of newly forming sea ice has mixed with icebergs to form what is called “brash ice.” Photo: M. Turrin

The focus today is on Getz ice shelf. Ice shelves form when ice flows off the land into the surrounding ocean, forming a thick apron of attached, but floating ice. The Getz shelf extends out several miles from where the glacier empties into the ocean. The shelves are deep floating blocks of ice ~ a km thick where they first meet the ocean and thinned to several hundred meters thick at their front edge. They are critical for the future stability of the Antarctic ice sheet as they provide a barrier that holds back the continental ice sheet, braking its flow from land into the ocean.

Image noting the location of some of the larger ice shelves around Antarctica (Image T. Scambos NSIDC)

Image noting the location and size of  a dozen or so of the larger ice shelves around Antarctica. Image: T. Scambos NSIDC

In all ~ 45 ice shelves adorn almost half the Antarctica coastline, and represent an area of ~1.5 million km², close to 10 percent of the total ice that covers Antarctica. Ten of these are considered major shelves, with the largest two nestled in the junctures where East and West Antarctic meet, filling in the space with California-sized blocks of ice: the Ross Ice Shelf (at 472,960 km²), where Lamont-Doherty currently has another Antarctic research project called Rosetta running, and the Filchner-Ronne (422,420 km²) across from it. Many of the shelves are smaller, yet each serves a valuable role in Antarctic ice stability, and thus they are a prime focus for examining change in Antarctica.

Tabular icebergs after separating fro the ice shelf line up along the front of Getz before moving out into the ocean. (Photo M. Turrin)

Large tabular icebergs after separating from the ice shelf line up along the front of Getz before moving out into the ocean. Photo: M. Turrin

Changes in Antarctic ice have been dominated by the interaction of the ice and the ocean, and because ice shelves extend out into the water, they are vulnerable to melt from the warmer ocean water. Melt can affect them in two ways, through thinning along their length and through causing a retreat of the “grounding line.”  The grounding line is the critical spot where the ice goes from being frozen all the way to the ocean floor (or bed) to where it begins to float in the ocean. The grounding line retreat results from warm water melting the ice back from its frozen base. Tracking any changes to the location of the grounding line tells us a lot about the vulnerability of the ice shelf and is critical to setting models.

Ice shelves sit primarily below the ocean surface. Getz measures close to 200 ft. at the front but with another 1000 ft. below the surface. The rich blue color along the front edge is from that deep reaching ice front. (Photo M. Turrin)

Ice shelves sit primarily below the ocean surface. Getz measures close to 200 ft. elevation above the ocean at the front, but has another 1000 ft. of ice below the surface. The rich blue color along the front edge is from that deep reaching ice front. Photo: M. Turrin

Getz ice shelf is our furthest flight mission of the campaign at close to 12 hours of flying, and it is our fifth mission this week, with each one clocking 11 plus hours of flight with prep and wrap-up added on either end. It could feel a bit like a rerun of the same movie, but it never does, and the wear of the long days doesn’t appear to show on the team. The purpose of today is to continue mapping the sub ice-shelf bathymetry using our gravimeter, as well as the ice surface and bedrock upstream of the grounding line using laser and radar. We need a complete look at the grounding line and the bed under the ice shelf, where warm ocean water can move in and circulate under the ice, in order to improve our models. Gravity is critical for uncovering the surface depths and contours under the ice shelves, as none of the other instruments on board are able to collect data through the water that lies under the shelf.

Mountain Protrusion

A set of mountains protrudes up through the ice at the west end of the survey line along the edge of the Getz Ice Shelf. Photo: M. Turrin

Because of the distance to Getz from our daily starting point in Chile, we have been building a set of data over a series of years, line by line. Each year we collect a repeat track and a new track. We know Getz has changed. Eighteen months ago in March 2015, a NASA image from space captured a Manhattan-sized iceberg (17 miles long) breaking off of Getz Ice Shelf. This break appears to have occurred at the end of the last austral summer in late February. Today we can see large sections of ice that will soon be calving, but what this means will need to be matched to the other measurements we are collecting before we know the full set of changes in Getz.

IceBridge: Since 2009, the NASA IceBridge project has brought together science teams to monitor and measure each of the ice features in order to improve our understanding of changes in the climate system and our models. Lamont-Doherty, under lead scientists Jim Cochran and Kirsty Tinto, has led up the gravity and magnetics measurements for these campaigns. This season alone, the project has logged 195 hours of flight time to date, and flown an equivalent of a third of the way to the moon.







Posted By: Kirsty Tinto on November 12, 2012

Mount Murphy rises through the ice sheet along the flank of West Antarctica, diverting the flow of ice around it (photo credit J. Yungel, NASA IceBridge Project)

1500 feet above the ground surface is where our suite of instruments normally operates, but for this flight we are taking them up higher, much higher, in fact over 20 times our normal range to 33,000 feet. Our flight plan is to repeat lines surveyed in a previous years by NASA’s Land, Vegetation Ice Sensor (LVIS) a scanning laser altimeter. LVIS has collected data as part of the IceBridge instrument suite in the past, but it was flown separately at high altitude on its own plane, in order to map large areas of both land and sea ice. This flight will refly some of LVIS’s work but using a subset of the instruments on our plane, narrow swath-scanning lidar, the digital mapping camera system, the gravimeter, and our depth radar.

At our higher elevation we will fly faster and can cover a lot of ground. The landscape of Antarctica can be hard to get ones head around – a glacier catchment is usually too big to fit into one field of view, so we see it bit by bit, and try to build up a physical picture in the same way we build up our understanding of the system – piece by piece. We have flown several missions into the Amundsen Sea region on the west Antarctic coast in the past, but this was the first time where we could really see the context of all of these different glaciers – flowing into the same embayment, forming ice shelves, calving ice bergs, and drifting northwards through the sea ice.

The flight offers views of some of the most noteworthy features in Antarctica. Pine Island Glacier, one of world’s fastest streaming glaciers, developed an 18 mile crack along its face in the fall of 2011 which spread further over the last few months. The crack will inevitably lead to breakage, dropping an iceberg which scientists have estimated will be close to 300 pound in size.

Crack along the front of the Pine Island Glacier as seen form the IceBridge forward facing camera.

The crack in the Pine Island Glacier as it is propagating further through the ice (Photo credit NASA IceBridge)

Bordering the glacier is one of two shield volcanoes we passed over during our flight. Pushing up through the Antarctic white mask, Mount Murphy diverts the ice streaming along the glacier. A steeply sloped massive 8 million year old peak, Mount Murphy pulls my thoughts back New York as it was named for an Antarctic bird expert from the American Museum of Natural History.

Mount Murphy, one of two shield volcanoes we overflew on this mission. (Photo K. Tinto)

From Mount Murphy we continue to the second shield volcano, Mount Takahe. Ash from 7900 years ago found in an ice core from the neighboring Siple Dome has been attributed to an eruption from this volcano. This massive potentially active volcano is about 780 cubic kms in size. The volcano was named by a science team participating in the International Geophysical Year (1957-8) after the nickname of the plane providing their air support …an unusual name for a plane as its origin is that of a plump indigenous Māori bird from New Zealand which happens to be flightless! Regardless the rather round Mount Takahe soars high above the glacier as we move overtop.

Mt. Takahe a slumbering volcano that is believed to have deposited evidence of an eruption in the ice almost 8000 years ago (Photo K. Tinto)

From there we fly over the tongue of Thwaites Glacier as it calves icebergs into the Amundsen Sea. To read more about Thwaites check out my first blog of the season:

The calving front of Thwaites Glacier. The neighboring glaciers of Pine Island and Thwaites are moving ice off West Antarctica into the surrounding ocean at a rapid rate (Photo K. Tinto)

For more on the IceBridge project visit:

Posted By: Kirsty Tinto on November 08, 2012

Travel to the Ronne Ice Shelf involved passing by the Ellesworth Mountains. The range contains Antarctica’s highest peak, Vinson Massif at 4897 meters of elevation.

Named after Edith Ronne, the first American woman to set foot on this southern continent, the Ronne Ice Shelf is tucked just to the East of the Antarctic Peninsula on the backside of the Transantarctic Mountains. With an area measured at 422,000 square kms, this is the second largest ice shelf in Antarctica. This vast icy expanse stretches into an indentation in the Antarctic coastline called the Weddell Sea, and gained some attention this past spring when scientists identified a mechanism that will force warming ocean water up against Ronne, which over time will cause it to thin and weaken (Hellmer, H. H. et al., 2012). Ice shelves are important barriers slowing the flux of ice moving off the land into the surrounding ocean. Any weakening in the tight connection of this ice to the land, either at the bottom where the shelf freezes to the ground below or where at the edges where it is tightly fused to the continent, can have major impacts on the speed and volume (flux) of ice moving off the land and into the oceans.

Annotated Antarctic map showing the area of study.

The current mission is being flown to measure the flux of ice currently coming into the Ronne Ice Shelf from the surrounding Antarctic landmass. To determine this we focus on the ‘grounding line’, the area where the ice changes from being frozen solid to the land below to floating as part of the ice shelf. To understand how much ice is moving over the grounding line, we have to understand how much ice is at the grounding line, and to do this we have to fly along the grounding line (or slightly inshore of it).

The majestic Ellsworth Mountains, formed about 190 million years ago, are the highest range in Antarctica, and steeper than the Tetons. Their original name, Sentinel Range, describes their posture, as they watch over the Weddell Sea and the Ronne Ice Shelf.

In many areas of Antarctica, even knowing where the grounding line is takes a lot of work. Much of that work is done using satellite data through a process called “interferometry”. This process compares the returning radar signal from different satellite passes to determine where the ice begins to move under the influence of the ocean tides. In this scale, ice that is responding to the rise and fall of the tides is floating ice, and from this we can mark the grounding line. While technique identifies the grounding line, it does not show how much ice is moving across it; to determine that we need to collect ice thickness measurements. For today’s flight we moved just inland of the grounding line for about half of the Ronne Ice Shelf collecting ice thickness and other supporting data that will begin to fill in this important information.

Reference: Hellmer, H. H. et al. Nature, 2012. DOI:10.1038/nature11064. 

For more on the IceBridge project visit:

Posted By: Kirsty Tinto on November 01, 2012

Sea Ice on the left, touching up against an ice shelf along West Antarctica. (Photo from the camera in the belly of the plane). The plane is flying at ~1500 ft. of elevation – the estimated field of view is ~450 meters.

One piece of our IceBridge mission focuses on sea ice here in the south. Sea ice in the northern regions has been reducing at dramatic rates over the last decade, setting a new record just this year, but the story in the south is not so clear. In fact, there has been a buzz that Antarctic sea ice extent may just be increasing while the Arctic ice is decreasing. The issue is a complex one and involves not just sea ice extent (how much surface area the ice covers) but sea ice thickness (total volume of ice). While the extent of Antarctic sea ice is increasing, we also need to understand how the thickness is varying.

One of the trickier items in measuring sea ice is making the raw measurements of thicker and thinner ice. With only satellite measurements it is hard to get the true thickness of the ice, since the surface of the ice is often covered with snow that needs to be accounted for in our calculations. Using the snow radar on the IceBridge mission we can work out how much of what the satellite is measuring is actually snow.

Bellinghausen sea ice labeled to show open water (dark areas), dark grey ice (less than 15 cm thick) and thicker light grey ice. Image from the NASA IceBridge camera.

The Bellinghausen Sea sits just to the west of the Antarctic peninsula and in the southern winter months is generally covered with sea ice. We have flown two Bellinghausen sea missions this season – one to map out to the furthest edges and another to looks at the gradient of sea ice change as you move away from the coast or shoreline. The second Bellinghausen mission was important because in running profiles in and out from the coast it allowed us to measure how ice thickness patterns vary with distance from the shore. We need to understand these patterns of ice thickness in the southern end of the planet, how they may be changing and what connection they have to the climate system.

An pice of land ice that has separated as an iceberg (shows with a bluish coloring, approximately 30-40 meters in length) travels trapped amidst the floating sea ice in Bellinghausen Sea, Antarctica.

There has been much less study done on southern sea ice than northern sea ice because we get very few opportunities to make the measurements we need. We have two high priority flights to the Weddell Sea (on the eastern side of the Antarctic peninsula), but so far it has not been possible to fly them because of the weather. Hopefully before the end of this season we will be able to fly both these flights and fill in more pieces in the sea ice story.

For more on the IceBridge project visit:

Posted By: Kirsty Tinto on October 29, 2012

Shackleton Ridge bordering the Recovery Ice Stream East Antarctica. (Photo M. Studinger, NASA)

Last year IceBridge had its first flights into East Antarctica when it flew some missions into the Recovery Glacier area. Recovery is a section of Antarctic ice that lies east of the peninsular arm of West Antarctica, tucked behind the Transantarctic Mountains, a dividing line that separates west from east. We know from Satellite data that Recovery and its tributaries have a deep reach, stretching well inland to capture ice and move it out into the Filchner Ice Shelf draining a large section of the East Antarctic ice sheet. But there is a lot we don’t know about Recovery because the remoteness of the area has limited the number of surveys.

Recovery Glacier with the lakes outlined in red. The yellow lines are the flight lines for the mission. (image courtesy of NASA IceBridge)

Several recent works have showed us that this area is important. Satellite measurements of the ice surface show small patches along the trunk of the glacier that are changing elevation more than their surroundings. These patches have been interpreted as lakes that lie under the ice sheet, coined the Recovery Subglacial Lakes. The lakes appear to drain and refill over time as the surface elevation over the lakes changes. To learn more about them and what they might tell us about the behavior of the glacier, we need to look under the ice.

But there is more we need to understand about this remote area, including simply needing to know the size and shape of the channel that delivers this ice out to the ice shelf and towards the Weddell Sea. Last year’s mission gave us some data points to outline the channel, but this year will help us provide a more complete imaging of what lies below this East Antarctic ice conveyor belt.

Recovery Glacier with “Which Way Nunatak” projecting up through the snow. A nunatak refers to an exposed section of ridgeline, or a peak that projects though the ice or snow in an ice field or glacier. (Photo by J. Yungel, NASA IceBridge)

We will fly cross sections along the lines of the retired ICESat satellite tracks, allowing us to compare the laser measurements we make of ice surface elevation to those made during the satellite mission. We will end the day flying along the Recovery channel to get another look at one of the interpreted lakes. Combining last years’ data, ICESat data and this year’s data will give us a better picture of the area that has been carved beneath the Recovery glacier, the amount of ice that can be moved through the glacier and its tributaries, and how the lakes under the ice might fit into the larger story.

Posted By: Kirsty Tinto on October 18, 2012
Snow blowing off the ice

Snow blowing off the ice and out to sea as we approached our survey site on
a windy day in the Amundsen Sea (30 knot winds were beneath us at times)

October 2012 IceBridge Antarctica resumes … Mission goal…monitoring the polar regions…Mission target… determine changes in ice cover and thickness, refine models for future sea level rise…Mission instruments…airborne geophysics. Good luck team.

The crews have spent the last few weeks in Palmdale, where the DC8 is based, for instrument installation and test flights prior to our move down to Punta Arenas, our home base for IceBridge Antarctica.

View From the DC8

View from the DC-8 as it travels from Santigo to Punta Arenas. Clockwise from top left: forward camera, nadir (directly below) camera, forward bay, aft bay both filled with equipment and supplies.

Instrument Run Down: We are flying with the same instrument suite as last year allowing us to see above, below and through the ice. Laser altimetry, for surface ice measurements, measured by the NASA Airborne Topographic Mapper, visible band photography, to allow for draped imagery, from NASA’s DMS (Digital Mapping System), three radar systems from Cresis to measure the ice thickness, composition and bed imagery (MCoRDS, Snow and KU band) and gravity to refine what is under the ice with Lamont using Sander Geophysics’ AIRGrav gravimeter.

ATM and the gravimeter both require GPS base stations on the ground throughout the deployment. Combined with the GPS receivers on the plane these allow very precise positioning of the aircraft, and the sensors on board, which is critical to all the measurements we make. Setting up the GPS stations is one of the first jobs in Punta Arenas.

Our First Mission for 2012 is Thwaites Glacier – Going Straight to the Heart of the Changes. On our way out of Punta Arenas, out past the airport, I noticed this feature in the landscape:
Paleo Landscape
It appears to be the paleo-shoreline from the last interglacial (~80,000 yr BP), when sea level was higher than present. The very flat terrain results in any sea level change causing a large shoreline retreat. Evidence like this of changing shorelines, is one method scientists use to determine past sea level under a different climate. As we study different areas around the world, we must account for the local changes in how the land has risen or fallen. Changes in sea level can be a combination of an adjusted world/ocean wide (eustatic) sea level and the more local response from the rebounding (isostatic ) of the land that was previously depressed under a glacier as local ice is unloaded during deglaciation. Here the history of the shoreline was governed by a combination of changes in eustatic sea level and the isostatic response to deglaciation of the local ice load (De Muro et al. 2012). Putting together information from around the world we eventually build up a picture of the global changes that have occurred in sea level. Changes in sea level are directly connected to our work monitoring polar ice.

When we fly over the ice, we are monitoring how the ice sheets are changing at present, and learning how to understand the complicated interactions between the atmosphere, the ocean and the ice. Studying this helps us to understand which ice bodies are most likely to contribute to sea level, how quickly they changed in the past, and how quickly they might change in the future. It’s good to get this reminder as we head out on our first flight – especially as it is to survey the area where the glacier switches from being frozen to the land below [the bed] to where it goes afloat, called the ‘grounding line’.

Our first flight of the season will be along the Thwaites Glacier. Thwaites and Pine Island Glacier are two ‘glaciers of interest’, both large outlet glaciers that serve as conduits out of the ice mass of the West Antarctic Ice Sheet (WAIS), moving ice off the land into the surrounding ocean, and long considered its Achilles heel. Thwaites glacier has a very wide region of fast ice flow over its grounding line, and a relatively small change in that width has the potential to greatly increase the flux of ice into the ocean. Through the radar and gravity measurements collected on previous IceBridge missions we have been able to get a sense of the bed shape tipping downward as you move inland from the ice edge, and where pockets of water lie under the icesheet. Our goal today is to collect enough data to develop a more complete image of what lies under the ice in this area.

Image of the inward sloping bed, and the ice front pinning to a rocky ridge. From: Tinto, K. J. and R. E. Bell (2011), Progressive unpinning of Thwaites Glacier from newly identified offshore ridge: Constraints from aerogravity, Geophys. Res. Lett., 38, L20503, doi:10.1029/2011GL049026.

2009 Operation IceBridge surveyed a grid in front of Thwaites grounding line and identified a ridge in the rock of the sea floor. In the last few months a large section of Thwaites glacial tongue broke off just seaward of that ridge. This mission will fly back and forth along nine lines parallel to the grounding line of Thwaites glacier. In combination with flights from previous years, this will give us a map of the grounding zone at 2.5 km spacing.

Thwaites Glacier

Thwaites Glacier from the air. Thwaites Glacier is so low and wide it is hard to get a good picture, but here you can see the fractured area on still-grounded ice where the fast flow is focused. You can also see the tracks from this region being carried out across the floating tongue. The grounding line is marked by the change to brighter white (more broken) ice just below the words “Fastest flow”. The eastern ice shelf is hidden by the wing of the plane, but the broken front of the floating tongue is in approximately the position of the submarine ridge of Tinto & Bell, 2011.


The tongue of Thwaites

Image of the tongue of Thwiates Glacier prior to the most recent ice ice section break off. Image from New Hampshire University MODIS Data Viewer tool.

We are hoping to learn more about goes on underneath this icy reach of the Earth each time we take flight.

Posted By: Kirsty Tinto on November 08, 2011
Pine Island Glacier, Antarctica

The leading edge of the floating ice tongue of the Pine Island Glacier Antarctica (photo by M. Wolovick)

By Kirsty Tinto & Mike Wolovick

As little as a few decades ago you could ask a scientist what it was like to monitor the changing ice in Antarctica and the response might have been “Like watching paint dry” — seemingly no change, with no big surprises and not too exciting. Well times have changed. The Ice Bridge Mission is deep into its third Antarctic season collecting data on the condition of the continental scale ice sheet and the floating sea ice that surrounds it, and has noted some exciting results.

Pine Island Glacier

The Pine Island Glacier Ice Stream survey plan was focused on \’mowing the lawn\’ or going back and forth across the glacier to capture changes in elevation from earlier surveys. (image Ice Bridge Program)

On a recent survey flight, which was designed to be fairly routine flying back and forth across the main trunk of Pine Island Glacier, a large crack was spotted in the floating ice tongue in the front of the glacier — a crack large enough to bury a building 16 stories high. This means more changes are coming in the future of this active ice stream.

Pine Island Glacier has been under intense focus as one of the fastest moving, and rapidly thinning glaciers in Antarctica. The planned survey was a grid back and forth across the main trunk of Pine Island Glacier. The pilots refer to this kind of survey as “mowing the lawn.” This type of data collection is essential for putting together a more complete “picture” of the glacier surface, depth, and its underlying surface, and its “grounding line.” The grounding line, shown here as the white line running through the image of the survey plan, is the front edge of where the glacier is frozen all the way to the bottom surface beneath it. The glacier extends beyond the grounding line but as a “floating tongue” of ice.

Pine Island Glacier

A large crack has developed in the floating tongue of the Pine Island Glacier an indication of a calving event in the future of this fast moving ice stream. (photo M. Wolovick)

Glacial tongues can be many meters thick, but because they rest on water they are susceptible to warming from the water below. It is not unexpected for sections of the tongues of glaciers to break off – in fact for this glacier scientists expect to see it occur about twice a decade (the last notable occurrence was in 2007). It is, however, impressive to see it actually developing, and to realize the scale of the crack as it begins – at least 50 meters deep, and up to 250 meters wide. Yes this is much better than watching paint dry.

Lamont-Doherty Earth Observatory has been a partner in this NASA led project collecting airborne gravity. The Ice Bridge Mission is designed to fill the gap between two satellite missions, IceSat I and IceSat II, collecting data on ice thickness in both polar regions. IceSat II is intended to be in orbit in another 4 to 5 years.

Posted By: Kirsty Tinto on November 20, 2010

Shadow of the DC-8 on Antarctic ice

The IceBridge mission has been having trouble getting flights up recently, which we have been assured is par for the course in this kind of work, but still it is frustrating! Here we are down in Punta Arenas waiting…waiting…waiting. We have faced a series of weather related stoppages and then the normal issues with equipment repairs causing this season to unfold with agonizing slowness. We were, of course, spoiled by all our successes of the prior campaigns, when flights seemed to lift off with uncanny regularity!

Kristy Tinto and Jim Cochran in Torres del Paine national park waiting for an 'all clear' to resume the mission flights.

However, last week there was a period where the weather and airplane were in synch and we got three flying days in a row, one to the South Pole with my colleague onboard, and two that I was on along the Western edge of the Antarctic Peninsula. The targets of my two flights were the ice shelves, where the ice flows off the Antarctic continent and ends floating in the sea. (see image)

Edge of floating ice shelf

I was eager to be involved in these two flights along the Antarctic Peninsula as they were to survey the Getz and the Dotson ice shelves which involves flying over the Amundsen Sea and past Thwaites Glacier. These floating ice shelves appear in a line, Thwaites, then Dotson, and then Getz (moving from the direction of tip of the peninsula downward). I have been working on data that were collected last year from the Thwaites area so it was good to at least be flying in the ‘neighborhood’. The Dotson flight was particularly useful for me, since the grid flown over it can be connected in to the Thwaites grid, extending my survey area and our understanding of that area.

I hadn’t been on a science flight before, so everything was new to me. There is a network on the plane so we can all sit with our laptops and follow our position on the map, see where we are going, how high and fast we are flying, and other information. There are additional cameras looking forwards and downwards, so we have a wide field of view in addition to looking out the window (which we did plenty of!) (see image)!

Scientists snapping images out the window

The different kinds of ice we flew over captured my interest…from icebergs in the open water, to big plates of sea ice, the expanse of flat, floating ice shelves and the crevassed glaciers. Each has a function in the polar region and studying the movements, expanse, depth of each can tell us a different piece of information about our changing polar region. There was a lot of variation in what was all essentially ice. For this flight, however, the targets was ice shelves, where the ice is floating on the sea. Collecting gravity data, which is Lamont’s role in this project, is important on these surveys because while the other instruments can measure the top (laser), bottom and internal surfaces of the ice (radar), they don’t “see” all the way down to the sea floor. The gravity measurement is controlled by the bathymetry of the sea floor, as well as by changes in geology, so we can use it to model the sea floor. Knowing what is under the shelves, how the ice is “hinged” to the continent, and how the ocean water beneath is coming into contact with the ice flowing off the continent is important to understanding how that ice might melt or move in the future.

On the trip home, I sat in the jump seat in the cockpit, a real treat! We flew back in to Punta Arenas over vegetated valleys, the landscape still marvelous but very different from how we had spent the day (see image).

Flying over Punta Arenas

Posted By: Kirsty Tinto on October 22, 2010

DC-8 plane outfitted for measuring the ice

Operation IceBridge Antarctica ramps up for a second year of ice surveys.  Originating from Chile, a series of airborne missions will be flown almost daily from the airbase in Punta Arenas.  Using a DC-8 jet airliner, the flights will run up to 11 hours each as they cross Drake’s Passage and the Southern Ocean to reach their destinations of monitoring Antarctic sea ice, the Antarctic peninsula and the western edges of the continent, before returning back to Chile each night. Flights will include some low altitude (~1,500 ft.) flights, and a few high altitude flights (~35,000 ft.).  For this season we will re-fly some of last year’s lines as well as adding some new locations to the flight plans.  One area to be resurveyed is an area of ongoing change – the Pine Island Glacier. This year the project design includes flying further back over the major trunk of the glacial ice stream in order to better understand the broader glacier dynamics.  The sea ice flights are also of interest to the science community since Antarctic sea ice, unlike Arctic sea ice, is actually growing in extent. Developing a better understanding of why this might be occurring is extremely important to understanding the full Antarctic climate dynamics.

The instruments on the plane include laser to map and identify surface changes (Laser Vegetation Imaging Sensor [LVIS] & Airborne Topographic Mapper [ATM]), radar to penetrate through the snow/ice and image below providing information on the bedrock support and internal ice characteristics, and gravity to measure the size and shape of any ocean water filled cavities at the outlets of some of the main fast-moving glaciers. Before embarking on the actual mission, test flights must be flown to check each instrument.  The five-hour test flights cruise over and around the Mojave desert, with different flight lines planned to test different instruments.  To me the most exciting was a ‘pitch and roll’ over Lake Mead for the LVIS scanning instrument to collect surface topography data.  The pitch is like putting the plane on a seesaw and tipping it forward and backward – which feels very impressive, and shows up in the vertical acceleration felt by the gravimeter and the butterflies in my stomach!  The roll maneuver involves flipping the plane side to side (although not all the way over), and looks very impressive out the window!  The instruments performed well so we move on to Chile.

The DC-8 carries 40 passengers and the seats are pretty big, so after a comfortable long-haul flight we spend Wednesday setting up the ground station – a hut where LVIS, ATM and gravity all have GPS antennae set up outside – and getting the gravimeter ready to measure.  Our gravity team includes Jim Cochran, and me from Lamont and Kevin and Sean from the Sanders gravity group. Because the gravimeter must stay plugged in at all times, by NASA guidelines it must be monitored round the clock.  We switch on and off this duty and every six hours swap generators and refuel.  Easy.   However the wind is blowing 76 km/hr, and gusting to 94 km/hr, so walking out to the plane is a challenge.  The good thing about Punta Arenas is that there are not many things blowing around – anything not tied down blew away a long time ago!

Posted By: Web Team on November 24, 2009

The Patagonian ice fields seen from 35,000 feet

For the first time in more than 40 days, the nose of the NASA DC-8 is pointing north after taking off from Punta Arenas airport. We have completed our Antarctic survey flights and are heading back home to Palmdale, California. But before we start climbing to cruising altitude we are flying at 300 ft above the Strait of Magellan just outside Punta Arenas to collect atmospheric chemistry data. After two passes over the strait, we head north towards Santiago and enjoy the spectacular view of the Patagonian Ice Fields and the Torres del Paine from 35,000 feet.

Over the past five weeks, the ICE Bridge teams have collected a landmark data set over Antarctica. We had originally planned to fly 17 missions but actually accomplished 21. We have flown more than 155,000 kilometers or almost 100,000 miles. This is almost four times around the world in 40 days. During this time, we collected high precision measurements of the ice surface elevation of many glaciers and ice shelves in Antarctica. We have also mapped the thickness of the glacier ice and snow cover, have measured the freeboards and snow thicknesses of the sea ice in the Weddell and Ross Seas, and have collected gravity measurements that will allow us to estimate the water depth beneath the floating glacier tongues. We have collected an enormous amount of data and are keen to analyze it with our colleagues when we are back in our labs. From the analysis of this data we will gain a much more detailed understanding of how the glaciers, ice sheets, and sea ice respond to changes in the climate system.

A project of this size is only possible with the support of many people. We could not have done this without the help and support of our Chilean friends and colleagues in Punta Arenas and Valdivia, the airport and hotel staff, and the many NASA and university people back home who have worked long hours to make this project happen. We thank NSF for giving us access to their forecasts, and help and assistance from the forecaster at the British Rothera Base (thanks Tony). For planning our flights, we also acknowledge our use of and dependence on the UCAR/NCAR NSF-supported Antarctic Mesoscale Prediction System. We had terrific aircraft crews both in the air and on the ground as well as excellent science teams. We all had a great time in Punta Arenas and are looking forward to come back next year for another ICE Bridge campaign over Antarctica.

Map with flight lines of the Operation ICE Bridge 2009 Antarctic campaign.

Map with flight lines of the Operation ICE Bridge 2009 Antarctic campaign.

Posted By: Web Team on November 17, 2009

Valley of Ice

The ice in this valley is moving towards the coast

Michael Studinger, Instrument Co-Principal Investigator, Lamont-Doherty Earth Observatory:

PUNTA ARENAS, Chile–The weather forecast for our survey over the Larsen C Ice Shelf looks good. Given the difficult weather over the past couple of days this is a welcome change. After studying satellite images and computer models and talking to the meteorologist at the Punta Arenas airport we decide to fly. We will follow the flow of ice from Antarctica’s interior to the ocean where the ice breaks into icebergs and eventually melts.

The flight will take us through an almost complete tour of the Antarctic cryosphere. Our tour begins over the small ice caps of the Antarctic Peninsula. The snow and ice that forms these ice caps eventually flows downhill through steep valleys, reaching glaciers and ice streams.

Larsen Ice Shelf

Glaciers flowing down steep valleys transport ice from the interior of Antarctica to the Larsen Ice Shelf near the coast

I am seated in the cockpit behind our two pilots to get a better view of the scenery. We are descending into a steep valley filled with ice on its way to the remnants of the Larsen B Ice Shelf that broke apart a few years ago. The ice here forms a huge floating surface that appears endless. Warm seawater lies below the ice; we are here to study how it melts the ice shelf.

The ice flowing into the valleys is pushing the ice shelves away.  Eventually huge ice chunks break off to form icebergs. Our next survey line takes us to the edge of the ice shelf where several gigantic icebergs can be seen floating in the distance, along with pools of open water. After crisscrossing what’s left of Larsen C we head back to the crest of the Antarctic Peninsula and repeat a different survey line. Each time I look out of the window I see a breathtaking but fragile landscape.

Our tour ends at the edge of Larsen C Ice, where sea ice meets open water.

Our tour ends at the edge of Larsen C Ice, where sea ice meets open water.

Heading home.

Heading home.