In a rapidly changing Arctic, one area might serve as a refuge – a place that could continue to harbor ice-dependent species when conditions in nearby areas become inhospitable. This region north of Greenland and the islands of the Canadian Arctic Archipelago has been termed the Last Ice Area. But research led by the 91̽�� suggests that parts of this area are already showing a decline in summer sea ice.

Last August, sea ice north of Greenland showed its vulnerability to the long-term effects of climate change, according to a published July 1 in the open-access journal .

“Current thinking is that this area may be the last refuge for ice-dependent species. So if, as our study shows, it may be more vulnerable to climate change than people have been assuming, that’s important,” said lead author , a polar scientist at the 91̽��Applied Physics Laboratory.

How the last ice-covered regions will fare matters for polar bears that use the ice to hunt for seals that use the ice for building dens for their young, and for walruses that use the ice as a platform for foraging.

“This area has long been expected to be the primary refuge for ice-dependent species because it is one of the last places where we expect summer sea ice to survive in the Arctic,” said co-author , a principal scientist at the 91̽��Applied Physics Laboratory.

The study focused on sea ice in August 2020 in the Wandel Sea, an area that used to be covered year-round in thick, multiyear ice.

“Sea ice circulates through the Arctic, it has a particular pattern, and it naturally ends up piling up against Greenland and the northern Canadian coast,” Schweiger said. “In climate models, when you spin them forward over the coming century, that area has the tendency to have ice survive in the summer the longest.”

Like other parts of the Arctic Ocean, the ice here has been gradually thinning, though last spring’s sea ice in the Wandel Sea was on average slightly thicker than previous years. But satellite images showed a record low of just 50% sea ice concentration on Aug. 14, 2020.

The new study uses satellite data and sea ice models to determine what caused last summer’s record low. It finds that about 80% was due to weather-related factors, like winds that break up and move the ice around. The other 20%, or one-fifth, was from the longer-term thinning of the sea ice due to global warming.

The model simulated the period from June 1 to Aug. 16 and found that unusual winds moved sea ice out of the area, but that the multiyear thinning trend also contributed, by allowing more sunlight to warm the ocean. Then, when winds picked up, this warm water was able to melt the nearby ice floes.

The record-low ice concentration in 2020 was surprising because the average ice thickness at the beginning of summer was actually close to normal.

“During the winter and spring of 2020 you had patches of older, thicker ice that had drifted into there, but there was enough thinner, newer ice that melted to expose open ocean,” Schweiger said. “That began a cycle of absorbing heat energy to melt more ice, in spite of the fact that there was some thick ice. So in years where you replenish the ice cover in this region with older and thicker ice, that doesn’t seem to help as much as you might expect.”

The results raise concerns about the Last Ice Area but can’t immediately be applied to the entire region, Schweiger said. Also unknown is how more open water in this region would affect ice-dependent species over the short and long terms.

“We know very little about marine mammals in the Last Ice Area,” said Laidre, who is also an associate professor in the School of Aquatic and Fishery Sciences. “We have almost no historical or present-day data, and the reality is that there are a lot more questions than answers about the future of these populations.”

Other co-authors are Michael Steele and Jinlun Zhang at the UW; and Kent Moore at the University of Toronto. The research was funded by the U.S. National Science Foundation, NASA, the Natural Sciences and Engineering Research Council of Canada; the National Oceanic and Atmospheric Administration; the Office of Naval Research; and the World Wildlife Fund Canada.

For more information, contact Schweiger at schweig@uw.edu, Steele at mas@apl.washington.edu or Laidre at klaidre@uw.edu. Note: Schweiger is on Central European Time. Steele and Laidre are on Pacific Time.

Our knowledge of the dwindling sea ice coverage in the Arctic Ocean comes mostly through satellites, which since 1979 have imaged the sea ice from above. The 91̽��’s Pan-Arctic Ice Ocean and Modeling System, or , is a leading tool for gauging the thickness of that ice. Until now that system has gone back only as far as 1979.

A now extends the estimate of Arctic sea ice volume back more than a century, to 1901. To do so it used both modern-day computer simulations and historic observations, some written by hand in the early 1900s aboard precursors to today’s U.S. Coast Guard ships.

“This extends the record of sea ice thickness variability from 40 years to 110 years, which allows us to put more recent variability and ice loss in perspective,” said , a sea ice scientist at the UW’s Applied Physics Laboratory and first author of the study published in the August issue of the Journal of Climate.

“The volume of sea ice in the Arctic Ocean today and the current rate of loss are unprecedented in the 110-year record,” he added.

PIOMAS provides a daily reconstruction of what’s happening to the total volume of sea ice across the Arctic Ocean. It combines weather records and satellite images of ice coverage to compute ice volume. It then verifies its results against any existing thickness observations. For years after 1950, that might be fixed instruments, direct measurements or submarines that cruise below the ice.

During the early 20^th century, the rare direct observations of sea ice were done by U.S. Revenue cutters, the precursor to the Coast Guard, and Navy ships that have cruised through the Arctic each year since 1879. In the project, the UW, the National Oceanic and Atmospheric Administration and the National Archives have been working with citizen scientists to to recover unique climate records for science. The new study is the first to use the logbooks’ observations of sea ice.

“In the logbooks, officers always describe the operating conditions that they were in, providing hourly observations of the sea ice at that time and place,” said co-author , a researcher at the . If the ship was in open water, the logbook might read “steaming full ahead” or “underway.” When the ship encountered ice, officers might write “steering various courses and speeds” meaning the ship was sailing through a field of ice floes. When they found themselves trapped in the ice pack, the log might read “beset.”

These logbooks until recently could only be viewed at the National Archives in Washington, D.C., but through digital imaging and transcription by Old Weather citizen-scientists these rare observations of weather and sea ice conditions in the Arctic in the late 1800s and early 1900s have been made available to scientists and the public.

“These are unique historic observations that can help us to understand the rapid changes that are taking place in the Arctic today,” Wood said.

Wood leads the U.S. portion of the Old Weather project, which originated in 2010 in the U.K. The weather observations from historic logbooks transcribed by Old Weather citizen scientists have already been added to international databases of climate data and were used in the model of the atmosphere that produced the new results.

Officers recorded the ship’s position at noon each day using a sextant. They would also note when they passed recognizable features, allowing researchers today to fully reconstruct the ship’s route to locate it in space and time.

While the historic sea ice observations have not yet been incorporated directly into the ice model, spot checks between the model and the early observations confirm the validity of the tool.

“This is independent verification that the model is doing the right thing,” Schweiger said.

The new, longer record provides more context for big storms or other unusual events and a new way to study the Arctic Ocean sea ice system.

“The observations that we have for sea ice thickness and variability are so limited,” Schweiger said. “I think people will start analyzing this record. There’s a host of questions that people can ask to help understand Arctic sea ice and predict is future.”

The PIOMAS tool is widely used by scientists to monitor the of Arctic sea ice. The area of Arctic sea ice over the month of June 2019, and the PIOMAS-calculated volume, were the second-lowest for that time of year since the satellite record began.

The lowest-ever recorded Arctic sea ice area and volume occurred in September 2012. And while Schweiger believes the long-term trend will be downward, he’s not placing bets on this year setting a new record.

“The state of the sea ice right now is set up for new lows, but whether it will happen or not depends on the weather over the next two months,” Schweiger said.

The other co-author is at the 91̽��Applied Physics Laboratory. The research was funded by the National Science Foundation, NASA, and the North Pacific Research Board.

For more information, contact Schweiger at schweig@uw.edu or 206-543-1312 and Wood at krwood@uw.edu 206-526-6862.

In February 2018, a vast expanse of open water appeared in the sea ice above Greenland, a region that normally has sea ice well into the spring. The big pool of open water in the middle of the ice, known as a , was .

New analysis by researchers at the 91̽�� and the University of Toronto Mississauga shows that odd winds are to blame, not simple global warming. The was published Dec. 6 in Geophysical Research Letters.

Although last winter did see unusually warm in the Arctic, the authors identify the cause to be strong surface winds triggered by a dramatic warming in Earth’s upper atmosphere, known as a “.”

“During these events, temperatures in the stratosphere — about 30 kilometers above ground level — can warm by 10 or 15 degrees Celsius in just a few days,” said lead author , at the University of Toronto Mississauga.

The sudden warming of 18 to 27 F at some 18 miles elevation shifts air pressure and thus circulation patterns. In February 2018, it caused winds from Siberia to blow cold air into Northern Europe, creating a weather system that became known as the “.” That same weather pattern drew warmer air north up the east coast of Greenland, and generated persistent strong winds.

“This [wind pattern] lasted a week, and these were the warmest temperatures and strongest winds observed in north Greenland since observations began in the 1960s,” Moore said. “Winds were close to hurricane force and temperatures were above freezing. Once we got that piece of the puzzle, we realized it could be wind rather than warmth that caused the polynya.”

The study relied on a 91̽��tool, the , or PIOMAS, to reconstruct sea ice conditions in the Arctic Ocean.

The authors used PIOMAS to run a simulation with the atmospheric conditions of 2018 but with thicker sea ice that was present in the Arctic in 1979, to see if thinner sea ice due to climate change caused the open water to appear. The patch of open water in that area was unprecedented in observations and lasted about three weeks, from mid-February through the first week of March.

“We used to ask the question hypothetically: What would have happened if the ice had been as thick as in 1979?” said co-author , a polar scientist at the UW’s Applied Physics Laboratory. “Now, we simulate it. The answer was that the thinning of the ice didn’t matter much, but strong winds were responsible.”

A longtime sea ice researcher, Schweiger was surprised. He thought thinning ice would be the decisive factor.

“But when we looked closer, it wasn’t. Letting your intuition guide your hypothesis, then letting yourself be convinced otherwise — that’s science,” he said.

The other co-authors on the study are and , both in the 91̽��Applied Physics Laboratory.

The 91̽��tool is also commonly used to gauge the total volume of Arctic sea ice in a given month. Overall the 91̽��tool shows the minimum volume of Arctic sea ice, reached in September, has recovered slightly from its all-time low in 2012, but is still following a long-term decline over the past four decades.

“We’ve lost about half of the extent, we’ve lost half of the thickness, and if you multiply these two things, we’ve lost 75 percent of the September sea ice,” Schweiger recently .

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For more information, contact Schweiger at schweig@uw.edu or 206-543-1312 and Moore at gwk.moore@utoronto.ca or 905-569-5766. (Note: Schweiger is traveling Dec. 17-27 with limited email access.)

Adapted from a University of Toronto .

A finds that a substantial chunk of summer sea ice loss in recent decades was due to natural variability in the atmosphere over the Arctic Ocean. The study, from the 91̽��, the University of California Santa Barbara and federal scientists, is published March 13 in Nature Climate Change.

“Anthropogenic forcing is still dominant — it’s still the key player,” said first author , a climate scientist at the University of California Santa Barbara who holds an affiliate position at the UW, where he began the work as a research scientist in the UW’s Applied Physics Laboratory. “But we found that natural variability has helped to accelerate this melting, especially over the past 20 years.”

The paper builds on previous work by Ding and other 91̽��scientists that found changes in the tropical Pacific Ocean have in recent decades that has boosted warming in that region.

The hot spot is a large region of higher pressure where air is squeezed together so it becomes warmer and can hold more moisture, both of which bring more heat to the sea ice below. The new paper focuses specifically on what this atmospheric circulation means for Arctic sea ice in September, when the ocean reaches its maximum area of open water.

“The idea that natural or internal variability has contributed substantially to the Arctic sea ice loss is not entirely new,” said second author , a 91̽�� polar scientist who tracks Arctic sea ice. “This study provides the mechanism, and uses a new approach to illuminate the processes that are responsible for these changes.”

Ding designed a new sea ice model experiment that combines forcing due to climate change with observed weather in recent decades. The model shows that a shift in wind patterns is responsible for about 60 percent of sea ice loss in the Arctic Ocean since 1979. Some of this shift is related to climate change, but the study finds that 30-50 percent of the observed sea ice loss since 1979 is due to natural variations in this large-scale atmospheric pattern.

“What we’ve found is that a good fraction of the decrease in September sea ice melt in the past several decades is most likely natural variability. That’s not really a surprise,” said co-author , a 91̽��professor of atmospheric sciences.

“The method is really innovative, and it nails down how much of the observed sea ice trend we’ve seen in recent decades in the Arctic is due to natural variability and how much is due to greenhouse gases.”

The long-term natural variability is ultimately thought to be driven by the tropical Pacific Ocean. Conditions in the tropical Pacific set off ripple effects, and atmospheric waves snake around the globe to create areas of higher and lower air pressure.

Teasing apart the natural and human-caused parts of sea ice decline will help to predict future sea ice conditions in Arctic summer. Forecasting sea ice conditions is relevant for shipping, climate science, Arctic biology and even tourism. It also helps to understand why sea ice declines may be faster in some decades than others.

“In the long term, say 50 to 100 years, the natural internal variability will be overwhelmed by increasing greenhouse gases,” Ding said. “But to predict what will happen in the next few decades, we need to understand both parts.”

What will happen next is unknown. The tropical Pacific Ocean could stay in its current phase or it could enter an opposite phase, causing a low-pressure center to develop over Arctic seas that would temporarily slow the long-term loss of sea ice due to increased greenhouse gases.

“We are a long way from having skill in predicting natural variability on decadal time scales,” Ding said.

The research was funded by NOAA, the National Science Foundation, NASA and the Tamaki Foundation. Other co-authors are Stephen Po-Chedley, Edward Blanchard-Wrigglesworth and Ryan Eastman in the UW’s Department of Atmospheric Sciences; Eric Steig in the UW’s Department of Earth and Space Sciences; and Michelle L’Heureux, Kristin Harnos and Qin Zhang at the National Oceanographic and Atmospheric Administration’s Climate Prediction Center.

###

For more information, contact Ding at qinghua@ucsb.edu, Schweiger at 206-543-1312 or axel@apl.uw.edu and Battisti at 206-543-2019 or battisti@uw.edu.

NOAA: NA15OAR4310162; NSF: ARC-1203425; NASA: NNXBAQ35G

So far, this summer’s melt season is following the overall downward trend in sea ice area, as seen from NASA satellites. A 91̽�� tool tallies a related value — the volume of floating Arctic ice. As of this week, it found the total mass of ice in the Arctic Ocean is at its second-lowest recorded volume for the beginning of July.

“The ice seems to be pretty thin,” said , a polar scientist with the UW’s Applied Physics Laboratory. “It’s essentially tied with 2011 and 2012, which were also pretty low at this time of year.”

Schweiger is one of the developers of the Pan-Arctic Ice Ocean Modeling and Assimilation System, or , which combines weather observations, sea-surface temperature and satellite pictures of ice coverage to compute ice volume and then compares that with on-the-ground measurements. The tool is widely used to assess the volume of ice in the Arctic Ocean, now an area closely looked at for fishing, navigation, oil exploration and even .

PIOMAS ice numbers starred in an animated graphic posted this week by a climate scientist at the University of Reading:

Meanwhile, in the Arctic, sea ice volume is at a record low for the time of year according to PIOMAS.

— Ed Hawkins (@ed_hawkins)

“I previously made a similar spiral for global temperatures which proved popular,” creator wrote in an email. “Sea ice was an obvious variable to look at next as it has a trend in the opposite direction.”

His graphic captures the overall downward trend in ice volume, as well as the seasonal cycle and the differences from one year to the next.

“It’s an interesting way of visualizing it,” Schweiger said. “By these circles getting smaller, you see overall that the ice volume is shrinking, but you also see the seasonal differences with September values decreasing more than the winter values.”

PIOMAS data had previously starred in the “” showing colored lines that each represent a month of ice volume spiraling in toward the center. It has also appeared as , animated , a featured in Wired magazine, and a of more standard graphs of Arctic sea ice.

Human-generated emissions are slowly boosting carbon dioxide levels to cause gradual temperature increases, which in turn create the closely-watched retreat of Arctic sea ice.

The March was the smallest in the satellite record, and the over the month of June was also a record low. The areal extent of Arctic sea ice, as by the U.S. National Snow and Ice Data Center in Colorado, is dancing around its 2012 record low.

“Whatever ice was gained in 2015, that seems to have been lost, and we’re continuing on a long-term downward trend,” Schweiger said.

The newly released June ice volume numbers from PIOMAS show an average volume of 16,500 cubic kilometers, which is about identical to 2011 and just above the 2012 all-time low.

“The June volume is just a little bit shy of the record, but the difference is within the noise in terms of the accuracy of the data,” Schweiger said. “Right now, based on volume, it’s technically a tie with 2012,” he said. “What that means for September is unclear.”

The fate of the ice this summer will depend on the weather over coming months, especially temperature, cloud cover, wind and storms.

Arctic sea ice reached an all-time low in September 2012. 91̽��research since that although a huge August storm helped break up more ice floes, that record was mainly due to warm temperatures.

In a recent compilation of expert for this year, Schweiger and 91̽��colleague estimated that Arctic sea ice will close out this fall at about 4.2 million square kilometers — more than the 3.63 million square kilometers low in 2012, but below the previous second-lowest level of 4.32 million square kilometers in 2007. If their prediction holds up, this summer will be among the three largest amounts of open water seen to date in the Arctic Ocean.

“I don’t think we know one way or the other,” Schweiger said. “It will essentially depend on the weather between now and the fall.”

###

For more information, contact Schweiger at axel@apl.washington.edu or 206-543-1312. Download the sea ice volume animation .

The , published in The Cryosphere, show a thinning in the central Arctic Ocean of 65 percent between 1975 and 2012. September ice thickness, when the ice cover is at a minimum, is 85 percent thinner for the same 37-year stretch.

“The ice is thinning dramatically,” said lead author , a climatologist at the 91̽��. “We knew the ice was thinning, but we now have additional confirmation on how fast, and we can see that it’s not slowing down.”

The study helps gauge how much the climate has changed in recent decades, and helps better predict an Arctic Ocean that may soon be ice-free for parts of the year.

The project is the first to combine all the available observations of Arctic sea ice thickness. The earlier period from 1975 to 1990 relies mostly on under-ice submarines. Those records are less common since 2000, but have been replaced by a host of airborne and satellite measurements, as well as other methods for gathering data directly on or under the ice.

“A number of researchers were lamenting the fact that there were many thickness observations of sea ice, but they were scattered in different databases and were in many different formats,” Lindsay said. The U.S. National Oceanic and Atmospheric Administration funded the effort to compile the various records and match them up for comparison.

The data also includes the NASA that operated from 2003 to 2008, that NASA is conducting until its next satellite launches, long-term under-ice from the Woods Hole Oceanographic Institution, and other measures from aircraft and instruments anchored to the seafloor.

The older submarine records were unearthed for science by former 91̽��professor Drew Rothrock, who of ice thickness to first establish the thinning of the ice pack through the 1990s. Vessels carried upward-looking sonar to measure the ice draft so they knew where they could safely surface. of those records found a 36 percent reduction in the average thickness in the quarter century between 1975 and 2000.

“This confirms and extends that study,” Lindsay said. The broader dataset and longer time frame show that what had looked like a leveling off in the late 1990s was only temporary. Instead, adding another 12 years of data almost doubles the amount of ice loss.

The observations included in the paper all have been entered in the that now includes around 50,000 monthly measurements standardized for location and time. The archive is curated by scientists at the 91̽��Applied Physics Laboratory and stored at the .

Lindsay also is part of a 91̽��group that produces a widely cited that combines weather data, sea-surface temperatures and satellite measurements of sea ice concentration to generate ice thickness maps. Critics have said those estimates of sea ice losses seemed too rapid and questioned their base in a numerical model. But the reality may be changing even faster than the calculations suggest.

“At least for the central Arctic basin, even our most drastic thinning estimate was slower than measured by these observations,” said co-author , a polar scientist at the 91̽��Applied Physics Laboratory.

The new study, he said, also helps confirm the methods that use physical processes to calculate the volume of ice each month.

“Using all these different observations that have been collected over time, it pretty much verifies the trend that we have from the model for the past 13 years, though our estimate of thinning compared to previous decades may have been a little slow,” Schweiger said.

The new paper only looks at observations up to the year 2012, when the summer sea ice level reached a record low. The two years since then have had slightly more sea ice in the Arctic Ocean, but the authors say they are not surprised.

“What we see now is a little above the trend, but it’s not inconsistent with it in any way,” Lindsay said. “It’s well within the natural variability around the long-term trend.”

Additional funding for the project was from the National Science Foundation and NASA.

###

For more information, contact Lindsay at rlindsay@uw.edu or Schweiger at 206-543-1312 or schweig@uw.edu.

While changes in weather may play a big role in short-term changes in sea ice seen in the past couple of months, changes in winds have apparently led to the more general upward sea ice trend during the past few decades, according to 91̽�� research. A new modeling study to be published in the shows that stronger polar winds lead to an increase in Antarctic sea ice, even in a warming climate.

“The overwhelming evidence is that the Southern Ocean is warming,” said author , an oceanographer at the 91̽��Applied Physics Laboratory. “Why would sea ice be increasing? Although the rate of increase is small, it is a puzzle to scientists.”

His shows that stronger westerly winds swirling around the South Pole can explain 80 percent of the increase in Antarctic sea ice volume in the past three decades.

The polar vortex that swirls around the South Pole is not just stronger than it was when satellite records began in the 1970s, it has more convergence, meaning it shoves the sea ice together to cause ridging. Stronger winds also drive ice faster, which leads to still more deformation and ridging. This creates thicker, longer-lasting ice, while exposing surrounding water and thin ice to the blistering cold winds that cause more ice growth.

In a computer simulation that includes detailed interactions between wind and sea, thick ice — more than 6 feet deep — increased by about 1 percent per year from 1979 to 2010, while the amount of thin ice stayed fairly constant. The end result is a thicker, slightly larger ice pack that lasts longer into the summer.

“You’ve got more thick ice, more ridged ice, and at the same time you will get more ice extent because the ice just survives longer,” Zhang said.

When the model held the polar winds at a constant level, the sea ice increased only 20 percent as much. A by Zhang showed that changes in water density could explain the remaining increase.

“People have been talking about the possible link between winds and Antarctic sea ice expansion before, but I think this is the first study that confirms this link through a model experiment,” commented , a polar scientist at the 91̽��Applied Physics Lab. “This is another process by which dynamic changes in the atmosphere can make changes in sea ice that are not necessarily expected.”

The research was funded by the National Science Foundation.

Still unknown is why the southern winds have been getting stronger. Some scientists have theorized that it could be related to global warming, or to the ozone depletion in the Southern Hemisphere, or just to natural cycles of variability.

Differences between the two poles could explain why they are not behaving in the same way. Surface air warming in the Arctic appears to be greater and more uniform, Zhang said. Another difference is that northern water is in a fairly , while the Antarctic sea ice floats in open oceans where it expands freely in winter and melts almost completely in summer.

The sea ice uptick in Antarctica is small compared with the amount being lost in the Arctic, meaning there is an overall decrease in sea ice worldwide.

Many of the global climate models have been unable to explain the observed increase in Antarctic sea ice. Researchers have been working to improve models to better reproduce the observed increase in sea ice there and predict what the future may bring.

Eventually, Zhang anticipates that if warmer temperatures come to dominate they will resolve the apparent contradiction.

“If the warming continues, at some point the trend will reverse,” Zhang said.

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For more information, contact Zhang at 206-543-5569 or zhang@apl.washington.edu.

“Every summer when the sun melts the surface the water has to go someplace, so it accumulates in these ponds,” said , a polar scientist at the 91̽��Applied Physics Laboratory and principal investigator since 2000 of the . “This doesn’t look particularly extreme.”

After media coverage in , and the U.K.’s , Morison returned from overseas travel late last week to a pile of media inquiries. Over the weekend the team posted an on the project website.

One of the issues in interpreting the image, researchers said, is that the camera uses a fisheye lens.

“The picture is slightly distorted,” said Axel Schweiger, who heads the Applied Physics Laboratory’s Polar Science Center. “In the background you see what looks like mountains, and that’s where the scale problem comes in – those are actually ridges where the ice was pushed together.”

Researchers estimate the melt pond in the picture was just over 2 feet deep and a few hundred feet wide, which is not unusual to find on an Arctic ice floe in late July.

In the midst of all the concern, the pool drained late July 27. This is the normal cycle for a meltwater pond that forms from snow and ice — it eventually drains through cracks or holes in the ice it has pooled on.

The now-infamous buoy was first plunked into floating ice in April, at the beginning of the melt season, about 25 miles from the North Pole. Morison drilled a hole about three football fields away for a second camera, which is pointing in a different direction and shows a more typical scene. Since then the ice floe holding both cameras has drifted about 375 miles south.

The U.S. National Science Foundation has funded an observatory since 2000 that makes yearly observations at fixed locations and installs 10 to 15 drifting buoys.

The buoys record weather, ice, and ocean data, and the webcams transmit images via satellite every 6 hours. Images show the ice, buoys and yardsticks placed in the snow to track the surface conditions throughout the summer melt season. Maybe the instruments will survive the summer without getting crushed by shifting ice to record data for another year. Maybe they will fall in the water and eventually wash ashore. Researchers place the buoys to try to maximize their useful lifetime.

While researchers say the so-called lake at the North Pole is not out of the ordinary, there is a lot of meltwater that could affect the sea ice in coming weeks, in the closely watched lead-up to the September ice minimum.

Last summer the sea-ice hit a record low in extent since measurements began in 1979. This year the melting started a bit later than usual, Schweiger said, but picked up in the last couple of weeks. Late summer is usually the strongest period of shrinking because the ice is already thin.

“Whether we’re going to see another record or not is still up in the air,” Schweiger said.

He flew over the ice last month in a to drop instruments that measure oceanic and atmospheric conditions and ice motion.

Morison was last on the ice in April when he deployed the buoys. His forecast for this summer, based on years of experience, is included on a compiled by the National Atmospheric and Oceanic Administration’s Seattle office.

Morison will not change his June estimate that this summer will come close to, but not pass, the 2012 record, but he is having his doubts. Looking at the photos from the recent flyover shows more melt along the Alaskan coast, and his experience suggests that ice is fragile.

“I think it’s going to be pretty close to last year,” Morison said. “Up in the Canada Basin the ice looks like Swiss cheese, with lots of holes. Even though the ice extent is pretty good, our thinking is that if there’s a big storm event we’re going to see a rapid breakup of that ice and it’s going to disappear pretty quickly.”

The 91̽��team manages another sea-ice tracking tool. The U.S. National Snow and Ice Data Center publishes daily images and calculations of , while the 91̽��group combines those satellite images and other data to tabulate . For many people, the UW’s monthly updates are a go-to source for getting the latest numbers on sea ice.

And while the North Pole lake news stories don’t exactly hold water, 91̽��researchers say that it at least shows public interest and concern.

“While the hoopla about Santa’s swimming pool was off the mark,” Morison said, “it is the long-term observational record from these buoys that provides the perspective needed to understand what really is going on.”

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For more information, contact Morison at 206-543-1394 or morison@apl.washington.edu and Schweiger at 206-543-1312 or axel@apl.washington.edu.

New satellite observations confirm a 91̽�� analysis that for the past three years has produced widely quoted estimates of Arctic sea-ice volume. Findings based on observations from a European Space Agency satellite, published online in , show that the Arctic has lost more than a third of summer sea-ice volume since a decade ago, when a U.S. satellite collected similar data.

Combining the 91̽��model and the new satellite observations suggests the summer minimum in Arctic sea ice is one-fifth of what it was in 1980, when the model begins.

“Other people had argued that 75 to 80 percent ice volume loss was too aggressive,” said co-author , a polar scientist in the 91̽��Applied Physics Laboratory. “What this new paper shows is that our ice loss estimates may have been too conservative, and that the recent decline is possibly more rapid.”

The system developed at the 91̽��provides a 34-year monthly picture of what’s happening to the total volume of Arctic sea ice. The Pan-Arctic Ice Ocean Modeling and Assimilation System, or , combines weather records, sea-surface temperature and satellite pictures of ice coverage to compute ice volume. It then verifies the results with actual thickness measurements from individual moorings or submarines that cruise below the ice.

“Because the ice is so variable, you don’t get a full picture of it from any of those observations,” Schweiger said. “So this model is the only way to reconstruct a time series that spans multiple decades.”

The 91̽��system also checks its results against five years of precise ice thickness measurements collected by a specialized satellite launched by NASA in 2003. The Ice, Cloud, and Land Elevation Satellite, or , measured ice thickness across the Arctic to within 37 centimeters (15 inches) until spring of 2008.

The U.K.’s satellite resumed complete ice thickness measurements in 2010; this is the first scientific paper to share its findings about the recent years of record-low sea ice.

Between 2008 and now, the widely cited 91̽��figures have because of the substantial ice loss they showed.

“The reanalysis relies on a model, so some people have, justifiably, questioned it,” Schweiger said. “These data essentially confirm that in the last few years, for which we haven’t really had data, the observations are very close to what we see in the model. So that increases our confidence for the overall time series from 1979 to the present.”

Arctic sea ice is shrinking and thinning at the same time, Schweiger explained, so it’s normal for the summer ice volume to drop faster than the area covered, which today is about half of what it was in 1980.

Schweiger cautioned that past trends may not necessarily continue at the same rate, and predicting when the Arctic might be largely ice-free in summer is a different question. But creating a reliable record of the past helps to understand changes in the Arctic and ultimately helps to better predict the future.

“One question we now need to ask, and can ask, is what are the processes that are driving these changes in the ice? To what degree is it ocean processes, to what degree is this in the atmosphere?” Schweiger said. “I don’t think we have a good handle on that yet.”

The 91̽��system was created by co-author , an oceanographer at the Applied Physics Laboratory. The 91̽��portion of the research was funded by NASA and the Office of Naval Research.

Other co-authors are first author Seymour Laxon, Katharine Giles, Andy Ridout, Duncan Wingham and Rosemary Willatt at University College London; Robert Cullen and Malcolm Davidson at the European Space Agency; Ron Kwok at NASA’s Jet Propulsion Laboratory; Christian Haas at York University in Canada; Stefan Hendricks at the Alfred Wegener Institute for Polar and Marine Research in Germany; Richard Krishfield at Woods Hole Oceanographic Institution; Sinead Farrell at the University of Maryland; and Nathan Kurtz at Morgan State University in Baltimore.

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For more information, contact Schweiger at 206-543-1312 or axel@apl.washington.edu.

American Geophysical Union / Natural Environment Research Council press release:

Article on NASA role:

But new results from the 91̽�� show that the August cyclone was not responsible for last year’s record low for Arctic sea ice. The study was published online this week in .

“The effect is huge in the immediate aftermath of the cyclone, but after about two weeks the effect gets smaller,” said lead author , an oceanographer in the UW’s Applied Physics Laboratory. “By September, most of the ice that melted would have melted with or without the cyclone.”

Recent research showed that the was the most powerful ever seen during the month of August, and the 13^th most powerful of all Arctic storms in more than three decades of satellite records.

“The storm was enormous,” said co-author , a polar scientist in the Applied Physics Laboratory. “The impact on the ice was immediately obvious, but the question was whether the ice that went away during the storm would have melted anyway because it was thin to begin with.”

The 91̽��team performed the climate scientist’s equivalent of a forensic exam: They ran a computer simulation of last summer’s weather and compared it against a second scenario that was identical except that there was no cyclone.

Results showed the storm caused the sea ice to pass the previous record 10 days earlier in August than it would have otherwise, but only reduced the final September ice extent by 150,000 square kilometers (almost 60,000 square miles), less than a 5 percent difference. By comparison, the actual minimum ice extent was 18 percent less than the previous record set in 2007.

The study also revealed a surprising mechanism for the cyclone-related melting. Earlier discussions about the cyclone’s effect had focused on winds breaking up the ice or driving ice floes into areas of warmer water. The results suggest that neither process led to much increase in melting.

Relatively recent research shows that in the summertime, thin ice and areas of open water allow sunlight to filter down to the water below. As a result, while a layer of ice-cold fresh water sits just beneath the sea ice, about 20 meters (65 feet) down there is a layer of denser, saltier water that has been gradually warmed by the sun’s rays.

Blowing on polar water is like blowing on a layered cocktail. When the cyclone swept over the drifting ice floes, underside ridges churned up the water to bring sun-warmed seawater to the ice’s bottom edge. The model suggests that during the cyclone there was a quadrupling of melting from below, and that this was the biggest cause for doubling ice loss during the three-day storm.

“We only looked at one big storm. If we want to understand how storms will affect the ice cover in the future we need understand the effect of storms in different conditions,” said co-author .

More sunlight reaches the water in a year with unusually thin summer ice, such as 2012, so this process is a potential multiplier effect for sea-ice melting.

The results are of interest beyond understanding climate change. As sea ice thins and melts, economic and political concerns require better sea-ice forecasts to protect ships and instruments that might travel in those waters.

“One thing we are working on, and that needs to be included in future computer simulations, is how bigger waves created by wind blowing over more extensive open water help break up the sea ice into floes, and how these smaller floes respond to warm water,” said co-author .

The research was funded by the , the U.S. and .

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For more information, contact Schweiger at 206-543-1312 or axel@apl.washington.edu.