IceBridge at the 2012 Goddard Science Jamboree

By George Hale, IceBridge Science Outreach Coordinator, NASA Goddard Space Flight Center

Operation IceBridge personnel participated in this year’sGoddard Science Jamboree on June 5. The yearly event is an opportunity forscientists and engineers at Goddard to share information about their meetingswith each other. This year’s Science Jamboree featured displays from a varietyof Goddard’s science missions, career panel talks, Hyperwall demonstrations,information sessions and a special lecture by Goddard Chief Scientist JimGarvin.

IceBridge project scientist Michael Studinger (left) and project manager Christy Hansen (right) at the Operation IceBridge display table

IceBridgeproject scientist Michael Studinger (left) and project manager Christy Hansen(right) at the Operation IceBridge display table. Credit: NASA/George Hale

Members of the Airborne Topographic Mapper (ATM) and Land,Vegetation and Ice Sensor (LVIS) instrument teams ran display tables with posters,photos and videos alongside a general IceBridge information display, adding awealth of information about the airborne polar mission. IceBridge scientistsand engineers answered questions about polar science, IceBridge’s instrumentsand the experience of surveying Arctic and Antarctic ice from the air. With thecompletion of a record-breaking Arctic campaign and several weeks of intenseAntarctic campaign planning ahead, the Science Jamboree was a good chance formembers of the IceBridge team to get together and show off all of their hardwork. Special thanks go out to all the people who took time out of their busy days to make the IceBridge presence at this year’s jamboree a success. 

Matt Beckley presented information on the LVIS instrument

Matt Beckley presented information on the LVIS instrument. Credit: NASA/George Hale

Weather and Operation IceBridge

By John Sonntag, OIB Instrument Team Lead, NASA

If you know the saying “make hay while the sun shines”, you’ve already got a pretty good idea of how weather affects flight operations for Operation IceBridge. Generally speaking, our flights require clear skies over the area in which we are operating on any given day. There are two good reasons for this. First, some of our sensors, including the Airborne Topographic Mapper and the Digital Mapping System, are optical instruments and need the sky between the aircraft and the ground to be cloud-free to obtain their measurements. Second, since we usually fly low and close to terrain (and sometimes amongst mountain peaks), our pilots need clear skies in order to see and avoid the terrain for flight safety reasons. These requirements mean that weather largely governs what we do on any given day, and makes it necessary for OIB project scientist Michael Studinger and myself to remain immersed in the minutiae of polar weather every day while we are in the field. On every potential flight day, we must make a decision about whether to fly and where to fly, and if we make the wrong decision we might face the mortifying prospect of returning from an expensive taxpayer-funded flight without science data to show for it. So far in the 3-year history of OIB, that has not happened, and Michael and I very much want to maintain that record.

Michael and I typically start studying the current weather patterns governing our operating areas at least a week prior to our deployment. It is helpful to develop a sense of context and a feeling for the current weather systems and their movements before we must begin making decisions on flight days. Our primary tools for this, and for all of our weather analysis tasks, are satellite imagery in several wavelengths, meteorological forecast models and point observations of current weather conditions from observers on the ground.

An early morning weather satellite image of Greenland and Arctic Canada, taken on 9 May 2012.

An early morning weather satellite image of Greenland and Arctic Canada, taken on 9 May 2012. This image is an infrared image from a NOAA polar orbiter, and while it shows significant cloud cover at several altitudes over western Greenland, we chose to fly a mission along a narrow corridor along the northwest coast of Greenland where the weather was clear. Credit: NOAA

Satellite imagery, most of which is provided by NOAA polar-orbiting satellites in our case, gives us a snapshot of the clouds over an area of interest. Imagery in the infrared band shows us not only the extent of the clouds over an area but also suggests the altitude of the cloud tops, since the infrared band is sensitive to temperature, and cloud temperatures are dependent on their altitude. Basically, bright white clouds are high, gray clouds are medium or low, and ground fog can sometimes be almost indistinguishable from the ice surface as their temperatures are similar. Visible imagery is better at showing us texture, which helps us distinguish between ice surface and fog, estimate the thickness and density of the cloud cover and determine the distance between cloud bases and the terrain beneath by virtue of the shadow they cast on the surface, especially when the sun angle is low. Another type of imagery we sometimes use is known as the “3 micron” band for its wavelength. This type is particularly sensitive to the amount of water vapor present in cloud masses.

We often refer to ground observations to help us refine our interpretation of satellite imagery, primarily because they provide a reliable measurement of the distance between the ground and the cloud bases. Sometimes the clouds are high enough and the terrain sufficiently benign that we are able to fly below the cloud bases, and point observations occasionally allow us to make such a judgment with some confidence we might not otherwise have. We must be careful, however, to remember that these observations are valid at one point only, while our flights cover large distances.

But for forecasting weather into the future, we are highly dependent on computer meteorological models, which predict what the weather may be like later in a day, or into the next day or beyond. Such information is critical for planning and optimizing our flight selections. For example, we might examine satellite imagery early on a potential flight morning and conclude the weather over our target is clear, but if a forecast model shows that the weather there will deteriorate by mid-day we would probably choose not to fly there. Sometimes the reverse occurs, where morning imagery might show marginal conditions over a target area but the forecast models confidently predict quick improvement. In such a case we might choose to launch a flight into the area, if our confidence in the model predictions is sufficient.

A typical flight day for me (and probably Michael as well) literally starts with weather as soon as I roll out of bed. The first thing I do every morning, even before brushing my teeth, is to open up my laptop and download a few satellite images to get a sense of cloud cover. That way I can mull it over while I get showered and into my flight suit and have breakfast. After breakfast, Michael and I, and our pilots, head to the local airport’s weather office to get their take on the weather where we are going. I cannot stress enough the importance we place on our discussions with these professional meteorologists, nor can I praise them enough for the help they invariably give us. Most of them seem to genuinely enjoy the professional challenge we bring to them, since the kind of flying we do, and the weather we are dependent on, are so different from those of the flight crews they normally deal with. In this morning weather briefing, we go over everything they have available, including satellite imagery, model predictions, point observations, and their own professional and experientially-derived “feel” for the conditions. Once we have gathered all the information available, it is decision time. We always remember that when we launch a flight, we are committing the U.S. taxpayer to pay many thousands of dollars to operate a big, expensive aircraft that day. So we take this decision very seriously, and at times it can be a rather nerve-wracking process.

Icebergs in a northwest Greenland fjord shrouded in fog.

Icebergs in a northwest Greenland fjord shrouded in fog. Credit: NASA/Jim Yungel.

Once in the air we constantly monitor the weather to see if it was as we expected, based on the morning weather briefing. It usually is, though the exact locations of cloud boundaries and ceilings are sometimes slightly different from what was predicted, and occasionally ground fog might exist where we did not expect it. We find that ground fog is consistently the most difficult aspect of polar weather to predict, although it has never adversely affected a flight to a serious degree. We also monitor the winds and compare these to the forecasts, which is important because winds can create turbulence under certain conditions, and turbulence can create a variety of problems for us.

Once we land, Michael and I immediately head back to weather office to get a forecast for the next day. Next, based on what I heard at this post-flight briefing and on further information I obtain from the internet, I prepare a weather briefing for the entire field team, which I give at our nightly science meeting. This briefing usually has two parts. First is a quick retrospective analysis of the day’s mission, comparing the weather we expected with what we actually encountered. Doing this on a daily basis helps us fine-tune our understanding of the performance of various weather models, our interpretation of imagery and our general decision-making process. Next I give an overview of our expectation of the next day’s weather and which flights might be best-suited for it. This enables the flight crew and the instrument operators to prepare for the next day’s activities.

The next morning, the process starts all over again. By the time we end a long deployment (the current one will be 11 weeks long), I look forward to spending entire days without looking at a weather image. But to be honest, I am at heart a weather geek, and after being back home for a while I miss the sense of connectedness I had to the natural world from remaining so immersed in meteorology for such a long time.

I have found that the key to successful weather-based decision-making is to consult as wide a variety of sources as possible, diligently calibrate oneself to the strengths and shortcomings of all weather models and other sources of data, and probably most importantly, simply stay on top of the weather situation multiple times each day. By doing this we can develop an almost intuitive sense for the evolving weather regime, which helps us quickly digest new information and interpret it correctly. Finally, I think it’s important to cultivate a sense of humility with regards to weather forecasting. Meteorology is a complex business and there is much we do not know. This is particularly true in the polar regions, because in contrast to places such as the continental US, the measurements that feed weather prediction tools are extremely sparse. In practice this sense of humility translates into keeping an open mind about the weather, avoiding coming to hasty conclusions before consulting every possible source and having contingency plans ready in case things do not work out exactly as we thought.

In the spirit of international collaboration: Honoring the Terra Nova Expedition

By Michael Studinger, IceBridge Project Scientist, NASA Goddard Space Flight Center/UMBC

Thule Air Base, Greenland – March 29, 2012 is a special day for polar researchers worldwide. It marks the centennial of Sir Robert Falcon Scott’s death on the Ross Ice Shelf. Many commemorative events have taken place around the world to remember the scientific accomplishments of the Terra Nova Expedition, particularly those of the Pole Party consisting of Robert Falcon Scott, Edward Wilson, Henry Bowers, Lawrence Oates and Edgar Evans. The most prominent event was a National Service of Commemoration for Captain Scott and the Pole Party at St. Paul’s Cathedral in London, with IceBridge’s own Seelye Martin attending as a guest of honor.

In 2008 I had the privilege to visit Captain Scott’s historic Terra Nova Hut on Cape Evans in Antarctica, and the geographic South Pole, where the National Science Foundation installed a sign bearing Scott’s famous quote said when the party realized the Norwegian expedition, led by Roald Amundsen, had been there first: “The pole. Yes, but under very different circumstances from those expected.” These are moments in my life that I will never forget. Walking through the Terra Nova Hut, which looked like it has been frozen in time, took my breath away.

Inside Captain Scott’s Terra Nova Hut on Cape Evans. The hut was built in 1911 by members of the British Antarctic Expedition (Terra Nova Expedition) and used as base for the trek to South Pole from which Scott and four of his team members never returned. The hut is remarkably well preserved but is undergoing restoration by the Antarctic Heritage Trust to protect it from further decay. The kitchen area on the left is one of the many areas inside and outside the hut that are being worked on. The hut is part of the 100 most endangered sites on the World Monuments Watch List. It is a remarkable place to be to say the least. Credit: Michael Studinger/NASA.

One hundred years later polar research has changed dramatically. On the day of the centennial, NASA’s Operation IceBridge and the European Space Agency’s CryoVEx campaign coordinated flights of two aircraft from different locations over the Arctic Ocean on a track flown shortly before by ESA’s CryoSat-2 spacecraft 600 km (370 miles) above us. We are able to do this because we have modern satellite images that are a few hours old and computer models showing the cloud cover in the survey area. We have modern means of communication that allow us to coordinate these science flights a few hours before takeoff. We know our position within a few feet and the NASA Airborne Science program flight tracker shows our position in real time. A lot has changed to say the least, but nevertheless operating in the remote polar regions remains a challenge even today. Modern navigation computers routinely get confused within a few miles of either the North or South Pole, the extreme cold still poses a challenge and weather predictions can be wrong. The safety and success of our operations is only possible because of extremely experienced and skilled members of the aircrew and instrument teams that excel in meeting the challenges of the polar environment every day.

Discovery Hut near McMurdo Station in Antarctica

McMurdo Station in Antarctica with the historic Discovery Hut in the foreground. The hut was built during Scott’s 1901-1903 expedition. The contrast between old and new is amazing. Observation Hill, the site of the Terra Nova memorial cross can be seen in the background on the right. Credit: Michael Studinger/NASA.

Today’s polar research is driven by a spirit of international collaboration and the joint NASA/ESA flight on March 29, 2012 is a fine example of what can be accomplished when many nations and organizations team up instead of competing with each other. Recognizing the enormous accomplishments of the early polar explorers, we dedicate this flight to the members of the Terra Nova Expedition, who died in Antarctica one hundred years ago.

NASA P-3 flight path

Flight path of the NASA P-3 Orion in yellow during the joint sea ice science mission with ESA’s CryoVEx airborne campaign stationed in Alert on Ellesmere Island and CryoSat-2.


New perspectives on the IceBridge sea ice campaign

By Nathan Kurtz, IceBridge scientist, NASA Goddard Space Flight Center/Morgan State Univ.

As the IceBridge Arctic sea ice campaign continues another successful year, I’ve been given this wonderful opportunity to discuss my experiences on the mission, and more importantly, how they relate to the critical science questions that need to be answered. I realize that there are many details I find intriguing as a scientist that are inherently uninteresting to non-scientists, so I won’t wax philosophical about how impressed I was to see things like the self-similar structure of deformation patterns in sea ice (if you actually came here for that, I apologize). My aim is to communicate the importance of what we are learning to the broader public who funds and ultimately benefits from this work. I hope you learn something about why we are devoting so many resources to this scientific study, as this is perhaps the most effective type of ‘bridge’ the IceBridge mission can make: to raise awareness of the state of the climate and present the scientific facts as we have gathered them through a long and arduous field campaign.

IceBridge science team member Nathan Kurtz checking out the sea ice conditions

IceBridge science team member Nathan Kurtz checking out the sea ice conditions. Credit: James Yungel/NASA.

This was my first trip to the ice-covered regions of the Arctic and I fully admit to reverting back to an excited childlike state of wonder as my initial flight to Thule, Greenland, touched down. It was quite striking to take in the sight of the vast snow-covered mountains and frozen sea, feel the bitter cold draining the heat and life from my body and realize that actual ‘monsters’ with an instinctive mindset to view humans as prey were all around. But I was shocked to see a hardened community of people standing resolute against these elements. Even more shocking, was to imagine why humans came here thousands of years ago without modern technology. What led them here? For me, the Arctic has always symbolized the unknown, but with hidden treasures awaiting anyone brave enough to explore it. But I realize my subjective symbolic interpretation is also remarkably universal in that native settlers, polar explorers and scientists must also have come to the Arctic with a desire to explore an unknown wilderness and gain some new knowledge from their experience. 

On the scientific end of this knowledge spectrum, recent studies have increasingly shown the importance of the Arctic to the climate. The once seemingly insignificant and remote Arctic region is now understood to be intimately connected to the rest of the planet. Sea ice variability affecting the severity of snow storms in Europe, melting sea ice increasing the absorption of sunlight by the Earth and melting ice sheets causing sea level rise are but a few of many such connections. We are learning that what happens in the Arctic will profoundly affect the whole of humanity all over the Earth. Viewed in this way, it is no longer a coincidence that humans have taken such a keen interest in the Arctic, and that this wild frontier is indeed a source of valuable knowledge waiting to be unearthed.

Looking out across the sea ice near Thule, Greenland

Looking out across the sea ice near Thule, Greenland. Credit: Nathan Kurtz/NASA

As a scientist, the purpose of my trip here is to learn more about the Arctic sea ice cover. My job is to use a combination of lasers, radars, cameras and infrared sensors to determine how the thickness of sea ice is changing, and whether any observed changes can be linked to the larger climate system. Flying over the sea ice with all the IceBridge instruments operating simultaneously has given me a whole new perspective on the mission. It has taken me from my normal desk job of looking at numbers on a computer screen, to the reality of what those numbers represent, and back again full-circle to connecting these concepts in a meaningful way. It has given me the opportunity to physically see that an increased laser surface elevation is actually a large sea ice pressure ridge, a widely spaced radar return is actually a snow drift. That, ultimately, all of the IceBridge results are indeed real and meaningful. It is this connection between numbers on a computer screen to the reality of the ground which will provide me and other scientists with the ability to come up with a rigorous scientific explanation of precisely what role sea ice thickness changes will have on the climate. 

In the course of my own analysis of the IceBridge data I have been constantly questioning my methods to ensure that my excursions into the abstract realm of mathematical and scientific theory do not lose sight of this connection to the things I’ve seen on the ground. Questions such as what do I do when I try to invert a matrix of IceBridge data and it explodes? How can I utilize statistics to determine just how accurate these measurements are? Are my solutions to these problems in tune with the physical environment I have witnessed? This ultimately translates into maintaining high standards and objectivity, which is critical to any scientific research area.

Sunrise over sea ice near the North Pole

Sunrise over sea ice near the North Pole. Credit: James Yungel/NASA

But this is, admittedly, my own subjective understanding of my role in this project. More important, is how my understanding and use of these concepts relates to the scientific results being obtained, and how these results can then be translated into a general statement for the public such as ‘the sea ice thickness decreased by x centimeters’ Towards this end, I and a large team of people have worked for the past two years on developing methods to turn the instrument data from IceBridge into clear and understandable scientific data products. We recently reached a major milestone in the project by demonstrating our ability to produce easy to understand products such as snow depth and sea ice thickness from past missions. In the interest of promoting honest and open exchange of scientific knowledge, we have given public access to these data sets (http://nsidc.org/data/idcsi2.html) in such a way that anyone can look at the latest results of the project. In doing so, we went from the realm of raw instrument data, to something that anyone can understand and interpret.

To further improve the utility of the IceBridge sea ice campaigns, we are attempting an unprecedented feat: to produce a quick version of the scientific products to support operational forecasting of sea ice. This is shaping up to be a monumental undertaking, and we are working hard to understand how to work with days-old field data. It remains to be seen what role IceBridge can play in sea ice forecasting and how we can interpret the data to come up with statements about the state of Arctic sea ice for the general public. But, so far the results from the first few flights look fantastic! We have also provided our preliminary results to support an ESA sponsored campaign conducting field missions in the area. Everything is proceeding in a positive direction, so stay tuned for more updates as the IceBridge mission continues!

Getting Ready for the 2012 Arctic Campaign

By Michael Studinger, IceBridge Project Scientist, NASA Goddard Space Flight Center/UMBC

Wallops Flight Facility, Wallops Island, VA – Welcome to the fourth annual Arctic campaign with NASA’s Operation IceBridge. Over 75 days, we will collect data with two aircraft over the Greenland Ice Sheet, the Arctic Ocean and the Canadian ice caps. We will be based in Kangerlussuaq and Thule Airbase in Greenland, and in Fairbanks, Alaska for sea ice flights over the Beaufort Sea.

During the past several weeks, Operation IceBridge teams have worked at NASA’s Wallops Flight Facility on the eastern shore of Virginia, installing cutting-edge laser altimeters and extremely sensitive radars that will allow us to measure changes in sea ice thickness in the Arctic Ocean. We will also be monitoring changes in the thickness of ice sheets and glaciers that cover most of the subcontinent of Greenland and the Canadian Arctic Archipelago. We will start our campaign with NASA’s P-3B Orion research aircraft from Wallops at Thule Airbase in northern Greenland with sea ice missions over the Arctic Ocean. The extent and thickness of the sea ice cover in the Arctic Ocean is declining quickly and we are there to take measurements that document this change from year to year. The second plane in this year’s Artic campaign, a Falcon HU-25 jet operated by NASA’s Langley Research Center in Hampton, Va., will join the campaign later in April carrying the Land, Vegetation, and Ice Sensor (LVIS), a high-altitude laser altimeter capable of measuring a 2-km-wide (1.2-mile-wide) swath.

The P-3B aircraft inside the hangar at NASA’s Wallops Flight Facility in Virginia.

The P-3B aircraft inside the hangar at NASA’s Wallops Flight Facility in Virginia. Credit: Michael Studinger.

Before we can start collecting data over the Artic we have to make sure that all installed sensors on the P-3 work and are calibrated. In order to make extremely precise laser altimeter measurements of the ice surface elevation we calibrate the instruments using target sites at the Wallops Flight Facility that we have surveyed on the ground. A second test flight takes us out over the Atlantic Ocean, some 200 miles away from the coast, where we can switch on the radar systems from the Center for Remote Sensing of Ice Sheets (CReSIS) at the University of Kansas, without interfering with other systems. We use the radar signal that is bouncing back from the ocean surface to calibrate the radars. We also did a couple of maneuvers at high-altitude over the Atlantic to calibrate the antennas of the ice-penetrating radar systems that we will use to survey the sea ice, glaciers and ice sheets.

Research flying has little in common with everyday air travel. One of the maneuvers that we do during the test flights is to fly the aircraft at a 90° roll angle with the wings perpendicular to the horizon. Fasten your seat belts! You will (hopefully) never experience something like this on a commercial flight.

The P-3B on the ramp before a test flight. The antennas of the ice-penetrating radar system can be seen mounted under the wings.

The P-3B on the ramp before a test flight. The antennas of the ice-penetrating radar system can be seen mounted under the wings. Credit: Michael Studinger.

We are collaborating with other experiments such as CryoVEx, the CryoSat-2 calibration and validation campaign from the European Space Agency. We will also work closely together with teams that work on the ground and take measurements over sea ice in the Arctic Ocean, and do coordinated flights with an ER-2 high-altitude aircraft from NASA’s Dryden Flight Research Center in Edwards, Calif. The ER-2, a civilian research version of the Air Force’s U-2 , will carry the Multiple Altimeter Beam Experimental Lidar (MABEL). The ER-2 will fly out of Keflavik, Iceland, and climb to 60,000 feet on its way to Greenland to measure the same tracks as the P-3B Orion.

We have now completed all our test flights here at Wallops and are ready to go to Greenland where we hope to map much of the sea ice cover over the Arctic Ocean and the Greenland Ice Sheet.

A Crack in the Pine Island Glacier Ice Shelf

A crack runs across the floating ice shelf of Pine Island Glacier in Antarctica, seen from NASA’s DC-8 on Oct. 14, 2011. Credit: Michael Studinger/NASA

Note: IceBridge flew a second mission to the Pine Island region on Wed., Oct. 26. Look for more imagery of the crack coming soon. To see more pictures from the Oct. 14 flight, go to the NASA_ICE flickr page.

After more than two weeks of successful flights over Antarctica and its surrounding waters and sea ice, one of the more interesting things NASA’s Operation IceBridge team has seen this year is a large crack running across the floating ice shelf of Pine Island Glacier. The team observed the crack on the DC-8’s Oct. 14 flight. The flight was designed to get better measurements of the region around the ice shelf’s grounding line — where the shelf meets the landmass under the water. It was also flown to collect data along lines that a ground-based expedition will traverse in the coming months. 

That data was collected, as expected. What wasn’t expected was the crack.

Pine Island is one of the largest and fastest-moving glaciers in Antarctica. It has captured scientists’ attention for years because of the rate at which its ice is thinning. The ice shelf thins, the grounding line retreats and the speed of the glacier increases. As it sits on bedrock below sea level — West Antarctica is the last place with such so-called “marine glaciers” — and drains about 10 percent of the West Antarctica ice sheet, scientists are concerned about the impact Pine Island’s continued thinning will have on sea level.

Ice shelves naturally calve icebergs to shed ice that flows from the landmass to the sea. However, given Pine Island’s prominence as a target of study for glaciologists, the crack is at the very least an interesting observation.

“It’s part of a natural cycle, but it’s still very interesting and impressive to see up close,” said IceBridge project scientist Michael Studinger. “It looks like a significant part of the ice shelf is ready to break off.”

The IceBridge team made a preliminary calculation that the area that could calve in the coming months covers about 310 square miles (800 square kilometers), Studinger said.

The team on the DC-8 observed the crack running across the breadth of the ice shelf. Credit: Michael Studinger/NASA

Peter Rejcek, Editor of The Antarctic Sun, wrote a piece about the crack that notes its location is about nine miles north of where a largely National Science Foundation-funded team, led by Bob Bindschadler of NASA’s Goddard Space Flight Center, will drill this December and January. The team will put instruments below the ice shelf to provide data about ice sheet-ocean dynamics.

Rejcek writes:

Bindschadler had previously calculated the propagation of earlier iceberg-releasing cracks at less than 50 meters per day. This crack must have moved much faster across the ice shelf, he said via e-mail.

“The characteristics of the PIG crack that I find surprising are the fact that it is so far across the ice shelf after not having been observed up until the end of last season,” he said.

The location of the crack is near where past rifts have appeared in the ice shelf, according to Bindschadler. He estimated that a new, rather large iceberg will probably form in the coming months, if not weeks.

“I hope that our field team will have enough time to get onto the ice shelf and set up GPS receivers before the calving event,” Bindschadler said. “We’d like to measure if the ice shelf notices the loss.”

Ted Scambos, lead scientist at the Boulder, Colo.-based National Snow and Ice Data Center, agreed that it’s likely that the crack is part of a natural cycle.

“These are cyclical, occurring every few years, very similar in size and even shape,” said Scambos via e-mail. “As a cyclical process, they are not part of the real climate-change/ice-shelf disintegration story.”

In 2002, the Larsen B Ice Shelf on the eastern side of the Antarctic Peninsula disintegrated in spectacular fashion, losing about 3,250 square kilometers of ice in a single season. More recently, the Wilkins Ice Shelf on the western side of the peninsula has started to collapse. Scientists believe both events are linked to climate change, though some researchers have suggested that wave action from distant storms could have helped break up the Wilkins Ice Shelf.

“If something different happened this time; for example, the pace of calvings changed, or this one was farther upstream from the past ones, then it might signal some major change in the Pine Island system,” said Scambos, adding that the area is changing in other ways, but the rate of calving has been steady over the last few decades.