Combined Arctic ice observations show decades of loss

Locations of Arctic Ocean sea ice thickness measurements from aircraft (AIR-EM and IceBridge), fixed points (other panels on the left), satellite (ICESAT) and under-ice submarines. Credit: R. Lindsay / Univ. of Washington.

from phys.org, March 5, 2015

It's no surprise that Arctic sea ice is thinning. What is new is just how long, how steadily, and how much it has declined. University of Washington researchers compiled modern and historic measurements to get a full picture of how Arctic sea ice thickness has changed.

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

"The ice is thinning dramatically," said lead author Ron Lindsay, a climatologist at the UW Applied Physics Laboratory. "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 Those records are less common since 2000, but have been replaced by a host of airborne and satellite measurements, as well as other methods for gathering data directly on or under the ice.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 average annual sea ice thickness, in meters, for the central Arctic Ocean. Red dots are submarine records. The green line is the long-term trend. Credit: R. Lindsay / Univ. of Washington.

The data also includes the NASA IceSat satellite that operated from 2003 to 2008, IceBridge aircraft-based measurements that NASA is conducting until its next satellite launches, long-term under-ice moored observations in the Beaufort Sea 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 UW professor Drew Rothrock, who used the U.S. Navy submarine measures of ice thickness to first establish the thinning of the ice pack through the 1990s. [Dr. Peter Wadhams of Cambridge University was using upward looking radar aboard submarines back in the 1970s to do this.  The article should have mentioned his work.] Vessels carried upward-looking sonar to measure the ice draft so they knew where they could safely surface. Further analysis of those records found a 36% 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 Unified Sea Ice Thickness Climate Data Record that now includes around 50,000 monthly measurements standardized for location and time. The archive is curated by scientists at the UW Applied Physics Laboratory and stored at the U.S. National Snow and Ice Data Center.

Lindsay also is part of a UW group that produces a widely cited calculation of monthly sea-ice volume 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 Axel Schweiger, a polar scientist at the UW 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."

 Explore further: Submarine data used to investigate turbulence beneath Arctic ice

http://phys.org/news/2015-03-combined-arctic-ice-decades-loss.html

Peter Sinclair: A warning from Jason Box and a Tale of Two Arctics

by Peter Sinclair, This Is Not Cool, March 16, 2015

At last week’s Arctic Summit in Oslo, put on by The Economist magazine, the atmosphere was sober.

Dark Snow Project founder Dr. Jason Box was the only scientist on the agenda, his presentation subtitled “A Warning.”

After a morning of presentations crafted to put a positive spin on the realization that an Arctic oil, minerals, and shipping Bonanza was not as imminent as once hoped, Dr. Box captured the attention of the assembled ministers, magnates, and academics. The whole room seemed to lean closer with each ever-more-ominous graph.

Climate change was a constant gorilla in the room, but there was another one, a bigger one, even more frightening to many of the players, — the creeping idea that energy prices, oil prices in particular, might have gone off script, and no one quite knows if they  are going to behave anymore as in the past.

There was agreement that energy development in the arctic is dormant for now due not only to oil prices, but to the recognition that the engineering and logistical barriers are far more difficult than imagined a few years ago. Shipping as well is under a cloud, not least because of questions about Russian intentions and behavior.

It’s not getting any more predictable up there.

Reuters:

A fall in oil prices may help long-term exploitation of fossil fuels in the Arctic by averting a short-lived “gold rush” into the vulnerable icy region, Norway’s Foreign Minister Boerge Brende said on Thursday. 

Exploitation of oil and gas required long planning to safeguard the fragile environment, which is heating up faster than the world average because of global warming, he said. 

“It is safe to assume that Arctic gas will have its day,” he said in a speech at an Arctic conference, saying that burning natural gas emitted half the amount of heat-trapping carbon dioxide as coal. 

Brende said some projections for an opening of the Arctic to shipping, oil and gas exploration and mining had been too optimistic amid a thaw that has cut the extent of winter sea ice on the Arctic Ocean close to a record low this month. 

“We should be very happy that there was not a ‘gold rush,’ ” he told reporters in Oslo. “A ‘gold rush’  is not positive, it’s throwing oneself at resources at breakneck speed.” 

“The Arctic is a very vulnerable area where we have to go step by step” with strong environmental rules, he said. 

Still, he said that fossil fuels would continue to dominate the world’s energy mix and would be needed from more Arctic areas. 

Statoil’s Snoehvit gas field, in the Barents Sea, is so far Norway’s only Arctic offshore field. Eni’s Goaliat field is due to start producing oil in mid-2015. 

Brent oil futures traded at $58 a barrel on Thursday, slightly more than half its average of around $110 from 2011-13. The fall has discouraged investments in the high-cost Arctic.

Meanwhile, at yet another conference on the future of the Arctic, the same week,  a more euphoric “Chamber of Commerce” atmosphere prevailed.

Scientific American:

ROVANIEMI, Finland—In one of this nation’s northernmost cities and at the close of a winter that citizens here have called unusually mild, foreign ambassadors spoke of their nations’ hope to do business in the Arctic, Finnish spokesmen outlined their plans to attract international money, and business owners burnished their cases for investment in the polar north. 

“Nordic lights is a good example of business actually nowadays,” Juha Mäkimattila, the chairman of the Lapland Chamber of Conference, said at a dinner for foreign guests, Wednesday, with a slideshow of aurora borealis photographs thrumming behind him. “We can actually make money on the northern lights from people from new parts of the world.” 

At the two-day Arctic Business Forum, hosted by the Lapland chamber, delegations from more than 20 nations, most which do not border the Arctic Circle, said the tone reflected a robust appetite for economic expansion, natural resource extraction and an optimistic prognosis for strong tourist spending. 

Meeting in a city that advertises itself on its website as “The Official Hometown of Santa Claus,” most speakers alluded to environmental management but didn’t get into the problems of melting permafrost or the additional threats of future oil spills or the loss of species. 

On both days, the tone was bullish. Diplomats from global trade and economic powers signaled their governments’ growing interest in Arctic transit and heavy shipping in the Arctic Ocean.

http://climatecrocks.com/2015/03/16/a-tale-of-two-arctics/

Limiting global warming to 2°C: the philosophy and the science

How much more glacial melting can the planet stand? NASA

by Lawrence Torcello and Michael Mann, The Conversation, October 21, 2014

Industrial civilization must become technologically, economically, politically, and morally sustainable to hold the earth’s temperature below 2 °C (3.6 °F) higher than its preindustrial average. The problem is not insurmountable. It is possible, then, that we’ll benefit in the long run from having to deal with human-caused global warming, by being forced to mature politically and ethically.

As of yet, however, the world has largely failed to move beyond moral, political, and economic parochialism. Our continued failure will supplant the promise of sustainability with a legacy of collapse.

At our present pace of fossil fuel burning we will, by 2036, exceed the 2 °C limit (using the Northern Hemisphere mean temperature on a true pre-industrial (1750-1849) baseline under the assumption of a mid-range (3 °C) equilibrium climate sensitivity). And if we reach 2 °C warming, then natural feedback could threaten to drive further warming, making it possible for warming in the range of 3 °C or more to occur. If temperatures warm 3 °C (5.4 °F) or more, we may simply be unable to cope with the consequences.

In short, our current model of development could prove catastrophic for human civilization and the natural world.

The philosophy

In the 18th century David Hume wrote provocatively:

It is not contradictory to reason to prefer the destruction of the whole world to the scratching of my finger.

Hume was not endorsing such judgments. Rather, he was saying that our reasoning tends to be framed by non-rational, and in his example, selfish passions. Cavalier attitudes about climate change in the regions most prepared to cope with it seem to confirm Hume’s insight.

In response to Hume, Immanuel Kant reasoned there was an ethical duty to treat others by standards consistent with one’s own moral status. Doing so encourages a cosmopolitanism that looks beyond national borders.

Kant advocated justice beyond borders.

The concept of “justice as fairness,” advanced more recently by John Rawls, recommends that benefits enjoyed by the most advantaged members of society contribute to the prospects of the least advantaged. Influentially, the contemporary philosopher Peter Singer argues that affluent citizens of the world have an ethical responsibility to assist the global poor and disenfranchised.

Any politically just and morally accountable framing of climate policy must involve consistently weighing the actions of affluent industrialized nations against their impacts on the least advantaged.

So far, the wealthiest nations of the world have exploited the benefits of fossil fuel extraction while securing a future of increased suffering for the planet’s least fortunate. Developing nations of the world cannot sustain a similar rate of carbon based growth to the one previously enjoyed by developed nations.

Those least responsible for climate change are most vulnerable to it, constrained by it, and face the greatest imminent danger from it. To avoid the dangerous comfort of provincialism we in the developed world must understand the dangers faced by those at the frontline of global warming impacts.

The science

Currently, at just 0.9 °C (1.6 °F) warming, sea levels have risen eight inches. As a result, millions in the developing world are increasingly vulnerable to coastal storm surges. Tropical cyclones have an ever more damaging reach over the coastal poor, while warming oceans ratchet their destructive power.

As the Antarctic and Greenland ice sheets continue melting, another three feet and possibly as much as six feet of sea level rise by 2100 can be anticipated.

This means the warming level already reached will likely displace millions of people worldwide. Entire island cultures may be scattered and their traditional ways of life destroyed. Any resulting refugee crisis will be exacerbated by a greater range of agricultural pests, tropical diseases, increasingly frequent heat waves, wildfires, droughts, and subsequent crop failures. Migrating climate victims will be at risk of further injustice as social and political tensions intensify.

Kiribati is under threat: it’s our responsibility to save it. David Gray

And to it, we must add a reckoning with what is now the greatest ongoing mass extinction period since dinosaurs wandered the earth. Despite having accessible public information about global warming for more than two decades, many countries continue emitting greenhouse gasses at record-breaking rates.

Unfair devastation

To be sure: the planet we hope to leave the youngest children alive today and their offspring will be a world of unfair ecological devastation, with little margin for error on their part. If we don’t take aggressive action now it will remain a world of increased suffering, hunger and starvation, and ever less biodiversity.

Members of the industrialized world shoulder a shared moral responsibility for the ongoing consequences of our current behavior. We have long understood how to curb global warming through carbon pricing agreements. Instead we have postponed action while many in the political and industrial sectors, with financial interests in collective inaction, encouraged (and in some cases financed) a phony, immoral, and dangerous attack on settled science.

Climate justice and practical necessity require that wealthy nations assist the developing world in addressing climate related threats while adapting sustainably. Likewise, wealthy nations must act aggressively in a sincere effort to avoid the 2 °C threshold.

Doing so is a moral and practical imperative that will require legally binding mitigation plans, increased investment in sustainable infrastructure, and renewable technologies.

If we fail to avoid 2 °C warming, a possibility we must be ready for, aggressive action taken now will still position the next generation to better build on our efforts—while learning from our mistakes. The difficulty of our situation is no excuse for moral dithering.

This article has been updated to include more detail about the basis for passing 2 °C by 2036.

https://theconversation.com/limiting-global-warming-to-2-c-the-philosophy-and-the-science-32074

Scientists probe poorly understood linkage between melting Arctic and extreme weather

by Christa Marshall, E&E reporter, Climate Wire, August 18, 2014

Snowmageddon in Washington, D.C. Extreme floods in the United Kingdom last winter. A Texas heat wave two years ago.

For scientists, they all may be a byproduct of a warming Arctic. Or they might not, as much of the research on causation is still in early stages.

A new review article, released yesterday in Nature Geoscience, offers one additional theory about the link between the Arctic and extreme weather in mid-latitudes, pointing to a possible connection between snow in Siberia and unusual events in much of the United States, Europe and East Asia. But ultimately, the synthesis paper reports that much of the science remains uncertain about the link, as there is contradictory evidence for all of the main theories.

"The discussion on the topic until now has been 'he said, she said' where the ideas presented have been of individual scientists and have covered the spectrum of all possible opinions. This is the first that a group of leading experts with varying opinions all on the same paper and is the most authoritative consensus on the subject," said Judah Cohen, a scientist at Atmospheric and Environmental Research Inc. and lead author of the review article, which included scientists from six universities, research institutes and NOAA.

Basic statistics initially appear to reveal a link between Arctic changes and weather elsewhere. Since the late 1970s, Arctic September sea ice has declined at a rate of 12.4% per decade. The Arctic region has warmed about twice the global average, a phenomenon known as Arctic amplification. At the same time, there has been a trend toward many types of extreme weather in mid-latitudes.

The amount of precipitation on very wet days has increased since the late 1990s in mid-latitudes, for instance, and the percentage of warm days exceeding the 90th percentile has increased from 10% before 1980 to 16% now, the paper notes.

Dynamics that conflict with climate models

The scientists focused on winter weather extremes, as that season has "not always followed the warming script," Cohen said. "While global warming theory is consistent with record warm temperatures and more intense precipitation events, it does not directly explain cold extremes," the paper says. For example, the number of days continuously below freezing has increased in mid-latitudes, a dynamic that is not consistent with the projections of climate models.

The scientists examined dozens of papers and categorized them into three main theories about a possible link between the Arctic and different types of mid-latitude extreme weather. One suggests that warming spurs extra snow over Eurasia, as well as sea ice loss, which in turn shifts storm tracks south.

A second -- and highly discussed -- hypothesis is that a warming Arctic causes the jet stream to weaken and meander more in a North-South direction. Weather systems embedded in the jet stream then move more slowly, allowing events such as lengthy heat waves.

"The temperature difference between the Arctic and mid-latitudes is lessening. This is important because the west to east winds of the jet stream are driven by that temperature difference," said Rutgers University scientist Jennifer Francis, the lead proponent of the theory, in congressional testimony last year. Francis -- one of the co-authors of the new review article -- argued that the lessening temperature differential drives the North-South movement of air.

The third concept -- relevant for winter extremes -- is that the loss of sea ice in the Barents and Kara Seas in fall and winter helps create atmospheric "waves" that transfer energy from the low to the high atmosphere, that in turn alters the deep pressure known as the polar vortex, helping send Arctic blasts south.

The researchers added a fourth theory, that this "wave" phenomena may be boosted by increased snow cover over Siberia in October as well, in conjunction with the loss of sea ice. Previously, sea ice and snow cover on land largely had been talked about separately with the wave theory. "They can amplify the same result," Cohen said.

Four conflicting theories

Each of the theories has drawbacks, according to the paper. While most models show that warming leads to a southward movement of storm tracks, others do not, Cohen said.

The jet stream theory is probably the most controversial, as it is the least studied of the three, even as it is the most discussed, he said. The concept was the focal point of a National Academy of Sciences report in April synthesizing input from an earlier scientific meeting on the plausibility of the Arctic-weather link.

While the jet stream theory is plausible, there are also forces working against it "that may be canceling each other out," Cohen said. Arctic warming is occurring more at the surface and not at jet stream latitudes, he said. The tropics are more where warming is occurring at high latitudes, so it's not clear how much that is countering any influence on the jet stream from the north, he said.

For all three theories, it also is unclear how much Arctic amplification may be caused by mid-latitude weather in the first place via transfer of heat, as opposed to the reverse. Cohen called for more Arctic monitoring stations of everything from humidity to temperature to get a firmer grasp of what's happening.

Earlier this year, five climate scientists wrote a letter in Science during then-frigid temperatures in the eastern United States, urging the public to not make immediate conclusions about a climate change connection to the extreme weather. "The research linking summertime Arctic sea ice with wintertime climate over temperate latitudes deserves a fair hearing. But to make it the centerpiece of the public discourse on global warming is inappropriate and a distraction," the scientists wrote.

While the new analysis does not get any closer to certainty on any of the theories, it was important to get many of the lead scientists studying the topic in consensus on one paper, to provide an information baseline, Cohen said.

"I think the fact that anything was written is an accomplishment," he said.

http://www.eenews.net/stories/1060004571

Peter Wadhams on the Arctic problem

Published on August 8, 2014, by Nick Breeze

Peter Wadhams is Professor of Ocean Physics in the University of Cambridge, and is an oceanographer and glaciologist involved in polar oceanographic and sea ice research and concerned with climate change processes in the polar regions. He leads the Polar Ocean Physics group studying the effects of global warming on sea ice, icebergs and the polar oceans. This involves work in the Arctic and Antarctic from nuclear submarines, autonomous underwater vehicles (AUVs), icebreakers, aircraft and drifting ice camps. He has led over 40 polar field expeditions.

Neven: More on Melt Ponds [on the Arctic sea ice]

by Neven, Arctic Sea Ice Blog, April 25, 2014

A really good paper has been published online a couple of days ago in Nature, called September Arctic sea-ice minimum predicted by spring melt-pond fraction. It's really good because it's interesting, short, and it confirms what I've been suspecting for a while now. And when a paper confirms what one is suspecting, it must be really good, right?

All joking aside, the paper by Schröder et al. presents evidence that melt ponds play a very important role at the start of the melting season, to the point that it can heavily influence the September minimum. The last two melting seasons actually proved to be a great lesson in this respect. 2012 had a really good* start to the melting season, so good that when bad weather showed up, it didn't really slow down sea ice loss, the trend lines just kept dropping (low sea ice volume also played a role, of course). The reverse was true in 2013: cold and cloudy weather during the first half of the melting season caused a lagged response during the short periods when the Sun and higher temps finally got to the ice.

What Schröder et al. did was develop a melt pond model and incorporate it into the larger Los Alamos sea-ice model called CICE. Here's what they came up with:

Our simulations show that melt ponds start to form in May, a maximum extent of 18% is reached in the climatological mean at mid-July, and there are hardly any exposed ponds left by mid-August. The strong interannual variability and the positive trend are striking. Whereas in 1996, the year with the highest September ice extent since 1979, the maximum pond fraction reaches only 11%, in 2012, the year with the lowest September ice extent, up to 34% of the sea ice is covered by ponds.

This is accompanied by the following figure:

 

 Based on their results, Schröder et al. conclude:

[T]he melt-pond fraction in May seems to have the strongest impact on the sea-ice state in the subsequent September. Our results confirm that the early melt season is decisive for the strength of the summer ice retreat.

(...)

We conclude that the inclusion of a realistic melt-pond model will transform future forecast and climate models in the Arctic regions and beyond.

 Although they didn't participate in last year's Sea Ice Outlook, they did make a prediction:

For September 2013 we forecast a mean ice extent of 5.55 0 ± 44 million km2, which is closer to the observed mean value of 5.35 million km2 than any of the 23 statistical,model and heuristic predictions presented at the Arctic Sea Ice Outlook webpage in July (median value of 4.0 million km2).

As we all know, last year's ASIB community prediction for the SEARCH Sea Ice Outlook was overly pessimistic, and off the mark by almost 2 million km2, much more than the other predictions. Because of low volume and a record amount of first-year ice, I personally thought the September minimum couldn't but end up somewhere between 2007 and 2012, at the very least. Most of us would probably have guessed differently, knowing just how low the melt pond cover fraction was in May 2013, and how influential this can be.

Which goes to show how incredibly handy it would be to have near real-time melt pond cover fraction data at our disposal, which we could then compare to data from the last 5-6 years. It wouldn't tell us anything conclusive about the melting season's final outcome (weather determines this), but combined with ice age distribution, and data on thickness and volume, it would give us a good idea of where things could or couldn't head.

The image above comes from a blog post from 2 years ago, wherein I mentioned melt pond data having been developed by the University of Hamburg's Klima Campus for the 2000-2011 period (also referenced in the Schröder et al. paper), using MODIS satellite data. Hopefully something similar comes along next year, as May 2014 is just around the corner.

Still, we now know that the start of the melting season can make it or break it.

---

* When I say 'good,' I mean 'good for melting,' not that Arctic sea ice loss is a good thing in itself.

The image at the top of the blog post was found here, with a nice quote by Don Perovich:

When Arctic melt ponds are sufficiently connected, as pictured here, they exhibit a property called universality that researchers believe is common to all complex, correlated systems.

http://neven1.typepad.com/blog/2014/04/more-on-melt-ponds.html 

NOAA Arctic Sea Ice Report of April 2, 2014

Arctic sea ice at fifth lowest annual maximum

Arctic sea ice reached its annual maximum extent on March 21, after a brief surge in extent mid-month. Overall the 2014 Arctic maximum was the fifth lowest in the 1978 to 2014 record. Antarctic sea ice reached its annual minimum on February 23, and was the fourth highest Antarctic minimum in the satellite record. While this continues a strong pattern of greater-than-average sea ice extent in Antarctica for the past two years, Antarctic sea ice remains more variable year-to-year than the Arctic.

Overview of conditions

Figure 1. Arctic sea ice extent for March 2014 was 14.80 million square kilometers (5.70 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data.
Credit: National Snow and Ice Data Center
High-resolution image

Arctic sea ice extent for March 2014 averaged 14.80 million square kilometers (5.70 million square miles). This is 730,000 square kilometers (282,000 square miles) below the 1981 to 2010 average extent, and 330,000 square kilometers (127,000 square miles) above the record March monthly low, which happened in 2006. Extent remains slightly below average in the Barents Sea and the Sea of Okhotsk, but is at near-average levels elsewhere. Extent hovered around two standard deviations below the long-term average through February and early March. The middle of March by contrast saw a period of fairly rapid expansion, temporarily bringing extent to within about one standard deviation of the long-term average.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of April 1, 2014, along with daily ice extent data for four previous years. 2013 to 2014 is shown in blue, 2012 to 2013 in green, 2011 to 2012 in orange, 2010 to 2011 in brown, and 2009 to 2010 in purple. The 1981 to 2010 average is in dark gray. Sea Ice Index data.
Credit: National Snow and Ice Data Center
High-resolution image

In the Arctic, the maximum extent for the year is reached on average around March 9. However, the timing varies considerably from year to year. This winter the ice cover continued to expand until March 21, reaching 14.91 million square kilometers (5.76 million square miles), making it both the fifth lowest maximum and the fifth latest timing of the maximum since 1979. The latest timing of the maximum extent was on March 31, 2010 and the lowest maximum extent occurred in 2011 (14.63 million square kilometers or 5.65 million square miles).

The late-season surge in extent came as the Arctic Oscillation turned strongly positive the second week of March. This was associated with unusually low sea level pressure in the eastern Arctic and the northern North Atlantic. The pattern of surface winds helped to spread out the ice pack in the Barents Sea where the ice cover had been anomalously low all winter. Northeasterly winds also helped push the ice pack southwards in the Bering Sea, another site of persistently low extent earlier in the 2013 to 2014 Arctic winter. Air temperatures however remained unusually high throughout the Arctic during the second half of March, at 2 to 6 degrees Celsius (4 to 11 degrees Fahrenheit) above the 1981 to 2010 average.

March 2014 compared to previous years

Figure 3. Monthly March ice extent for 1979 to 2014 shows a decline of 2.6% per decade relative to the 1981 to 2010 average. Credit: National Snow and Ice Data Center. High-resolution image

Average ice extent for March 2014 was the fifth lowest for the month in the satellite record. Through 2014, the linear rate of decline for March ice extent is 2.6% per decade relative to the 1981 to 2010 average.

An increase in multiyear ice

Figure 4. Imagery from the European Advanced Scatterometer (ASCAT) show the distribution of multiyear ice compared to first year ice for March 28, 2013 (yellow line) and March 2, 2014 (blue line).
Credit: Advanced Scatterometer imagery courtesy NOAA NESDIS, analysis courtesy T. Wohlleben, Canadian Ice Service
High-resolution image

The extent of multiyear ice within the Arctic Ocean is distinctly greater than it was at the beginning of last winter. During the summer of 2013, a larger fraction of first-year ice survived compared to recent years. This ice has now become second-year ice. Additionally, the predominant recirculation of the multiyear ice pack within the Beaufort Gyre this winter and a reduced transport of multiyear ice through Fram Strait maintained the multiyear ice extent throughout the winter.

In Figure 4, Advanced Scatterometer (ASCAT) imagery reveals the distribution of multiyear ice compared to first year ice for March 28, 2013 (yellow line) and March 2, 2014 (blue line). The ASCAT sensor measures the radar–frequency reflection brightness of the sea ice at a few kilometers resolution. Sea ice radar reflectivity is sensitive to the roughness of the ice and the presence of saltwater droplets within newer ice (and, later in the season, the presence of surface melt). Thus older and more deformed multiyear ice appears white or light grey (more reflection), whereas younger, first-year ice looks dark grey and/or black.

Ice age tracking confirms large increase in multiyear ice

Figure 5. The map at top shows the ages of ice in the Arctic at the end of March 2014; the bottom graph shows how the percentage of ice in each age group has changed from 1983 to 2014.
Credit: NSIDC, Courtesy M. Tschudi, University of Colorado. High-resolution image

Satellite data on ice age reveal that multiyear ice within the Arctic basin increased from 2.25 to 3.17 million square kilometers (869,000 to 1,220,000 square miles) between the end of February in 2013 and 2014. This winter the multiyear ice makes up 43% of the icepack compared to only 30% in 2013. While this is a large increase, and may portend a more extensive September ice cover this year compared to last year, the fraction of the Arctic Ocean consisting of multiyear ice remains less than that at the beginning of the 2007 melt season (46%) when a large amount of the multiyear ice melted. The percentage of the Arctic Ocean consisting of ice at least five years or older remains at only 7%, half of what it was in February 2007. Moreover, a large area of the multiyear ice has drifted to the southern Beaufort Sea and East Siberian Sea (north of Alaska and the Lena River delta), where warm conditions are likely to exist later in the year.

Satellite Observations of Arctic Change

NSIDC now offers a new Web site, Satellite Observations of Arctic Change (SOAC)  with interactive maps of the Arctic based on NASA satellite and related data. The site allows you to explore how conditions in the Arctic have changed over time. Data sets include air temperature, water vapor, sea ice, snow cover, NDVI, soil freezing, and exposed snow and ice. Time periods vary by data set, but range from 1979 to 2013. You can animate a time series, zoom in or out, and view a bar graph of anomalies over time. Links to the source data and documentation are also included. Additional pages provide brief scientific discussion, and overviews of the scientific importance of these data. SOAC was developed with support from NASA Earth Sciences.

Reference

Stroeve, J., L. Hamilton, C. M. Bitz, and E. Blanchard-Wrigglesworth. 2014. Predicting September Sea Ice: Ensemble Skill of the SEARCH Sea Ice Outlook 2008–2013. Geophysical Research Letters, Accepted, doi: 10.1002/2014GL059388.

https://nsidc.org/arcticseaicenews/

NASA: Arctic Melt Season Lengthening 5 days per decade

from NASA, April 1, 2014

A new study by researchers from the National Snow and Ice Data Center (NSIDC) and NASA shows that the length of the melt season for Arctic sea ice is growing by several days each decade. An earlier start to the melt season is allowing the Arctic Ocean to absorb enough additional solar radiation in some places to melt as much as four feet of the Arctic ice cap’s thickness.

"The Arctic is warming and this is causing the melt season to last longer," said Julienne Stroeve, a senior scientist at NSIDC, Boulder and lead author of the new study, which has been accepted for publication in Geophysical Research Letters. "The lengthening of the melt season is allowing for more of the sun’s energy to get stored in the ocean and increase ice melt during the summer, overall weakening the sea ice cover."

A short video summarizes new findings about Arctic sea ice and warming oceans.  Play it!

Arctic sea ice has been in sharp decline during the last four decades. The sea ice cover is shrinking and thinning, making scientists think an ice-free Arctic Ocean during the summer might be reached this century. The seven lowest September sea ice extents in the satellite record have all occurred in the past seven years.

To study the evolution of sea ice melt onset and freeze-up dates from 1979 to the present day, Stroeve’s team used passive microwave data from NASA’s Nimbus-7 Scanning Multichannel Microwave Radiometer, and the Special Sensor Microwave/Imager and the Special Sensor Microwave Imager and Sounder carried onboard Defense Meteorological Satellite Program spacecraft. When ice and snow begin to melt, the presence of water causes spikes in the microwave radiation that the snow grains emit, which these sensors can detect.

Results show that although the melt season is lengthening at both ends, with an earlier melt onset in the spring and a later freeze-up in the fall, the predominant phenomenon extending the melting is the later start of the freeze season. Some areas, such as the Beaufort and Chukchi Seas, are freezing up between 6 and 11 days later per decade. Although melt onset variations are smaller, the timing of the beginning of the melt season has a larger impact on the amount of solar radiation absorbed by the ocean, because its timing coincides with when the sun is higher and brighter in the Arctic sky.

Despite large regional variations in the beginning and end of the melt season, the Arctic melt season has lengthened on average by 5 days per decade from 1979 to 2013.

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Credits:

Production editor: Dr. Tony Phillips | Credit: Science@NASA

http://science.nasa.gov/science-news/science-at-nasa/2014/01apr_arcticice/