Paul Beckwith on Arctic sea ice

Arctic Sea Ice: Everything You Need To Know
Paul Beckwith

 

Every summer now, there are many people anxiously monitoring the seasonal melt-back of the Sea Ice that covers the Arctic Ocean. One of these summers, likely within the next 5 years we will end up with no sea ice left at the end of the summer. This “blue-ocean” event will change our climate & lives, in numerous ways.


I give you the knowledge and links to see for yourself what is happening to the Arctic Sea Ice over the 2017 melt season, and discuss what happens next.

Global Sea Ice Values - Arctic and Antarctic - are Plummeting

From Pole to Pole, Global Sea Ice Values are Plummeting

During the record hot year of 2016, both Arctic and Antarctic sea ice extents took a huge hit.

Robertscribbler,

15 November, 2016

Extreme warmth in the Arctic helped to produce leading losses there. Values that began during January at 1 million square kilometers below average have steadily declined as the months progressed to near 2 million square kilometers below average. Meanwhile, the Antarctic — which began the year at near average sea ice extent values — saw significant losses as the region grew anomalously warm during austral spring. Today, sea ice extent values surrounding the Antarctic are now also just shy of 2 million square kilometers below average.

(Zachary Labe, one of the most well-recognized up and coming U.S. climate scientists, has produced this graph based on NSIDC recorded global, Arctic, and Antarctic sea ice values. As you can see, global sea ice extent during the hottest year on record has steadily plummeted to near 4 million square kilometers below average as the months progressed. Image source: Zack Labe’s Sea Ice Figures. Data source: NSIDC. You can also follow Zack’s informative twitter feed here.)

In total, global sea ice coverage is now about 3,865,000 square kilometers below average.

If you think that number sounds really big, it’s because it is. It represents a region of lost ice nearly 40 percent the size of the land and water area of the entire United States including Alaska and Hawaii. To visualize it another way, imagine all of the land area of Alaska, California, Texas, Montana, Arizona and New Mexico combined and you begin to get the gist.

Sea Ice Coverage — An Important, But Complex Climate Indicator

Many climate specialists have viewed sea ice as a kind of climate change canary in the coal mine. Sea ice sits upon the warming oceans and beneath a warming atmosphere. And these oceans are now taking up the majority of the heat being trapped in the atmosphere by fossil fuel emissions. Warming ocean surfaces have a higher specific heat value than the air and this greater overall energy capacity in warming regions generates a substantial blow to ice coverage even if the initial water surface temperature swing is only moderate.

Once sea ice is lost for a significant period, a kind of feedback loop comes into play where dark ocean surfaces trap more of the sun’s rays during polar summer than once-white ice coverage — which previously reflected radiation back toward space. This newly absorbed heat is then re-radiated back into the local atmosphere during polar fall and winter — creating an inertial barrier to ice reformation and ultimately generating a big jump in seasonal ocean and atmospheric surface temperatures.

(Highly pronounced ocean surface warming coupled with warm air invasions appears to be generating the extreme losses to sea ice now seen in the Arctic. The Barents Sea, shown above, has seen particularly extreme warming. Note the 11 C above average hot spot near the sea ice edge zone. In the Antarctic, the causes of losses remain uncertain. However, atmospheric warming and shifts in the circumpolar winds appear to be producing this effect even as slightly cooler than average surface waters remain in place — possibly due to storm related Southern Ocean upwelling and increasing fresh water outflows from Antarctic glaciers. Image source: Earth Nullschool.)

This dynamic is particularly pronounced in the Arctic where a thawing ocean surrounded by warming continents tends to readily collect heat even as atmospheric energy transfers from the south, in the form of warm wind events, have grown more pronounced. An effect related to the climate change influence known as Northern Hemisphere Polar Amplification.

In the Antarctic, the stormy Southern Ocean generates up-welling. This dynamic tends to cool the ocean surface even as it transfers heat into the deeper ocean. And increasing stormy conditions surrounding Antarctica related to climate change can intensify this effect. In addition, warm bottom waters melting sea-fronting glaciers in Antarctica produce a lens of fresh water which cools the surface and also traps heat below. So the signal coming from Antarctica with regards to sea ice has tended to be more mixed — with atmospheric warming and changes in wind patterns generating more variable sea ice impacts relative to the Arctic. So this year’s sea ice losses there are more difficult to directly link to climate change even though climate change related influences on the physical system in the Antarctic and among its surrounding waters are becoming more and more apparent.

Zack Labe notes that:

The Arctic sea ice anomaly, however, fits with the ongoing Arctic amplification trend of thinning sea ice and loss of old ice. Additionally, it has been well noted in previous literature (i.e., http://onlinelibrary.wiley.com/doi/10.1029/2010GL044136/full …) concerning the increasing fall temperatures in the Arctic and possible causes.

Major Volume Losses From 2015 to 2016

Despite big losses to sea ice surrounding the Antarctic this fall, it is the Arctic where the damage and risk of further loss is most pronounced. Particularly, reductions to thicker, multi-year ice in the Arctic during 2015 to 2016 have been exceptionally severe:

 

In the above images, we see a comparison between late November sea ice coverage and thickness as provided by the U.S. Navy ARCc model. The left frame represents late November of 2015 and the right frame represents projected values for November 20, 2016. Note the greatly reduced coverage in the 2016 image. But even more noteworthy is the substantial loss of thicker ice in the Arctic Ocean north of the Canadian Archipelago and Greenland.

These two images tell a tale of a great loss of sea ice volume. One that the sea ice monitor PIOMAS confirms. According to PIOMAS, ice volume values during October were tracking near lowest levels ever recorded. And continued heat into November generates a concern that a period of new record low volume levels may be on the way.

But it’s not just the record low values that should be a concern. It’s the location of the remaining thick ice that’s a worry as well. For a substantial portion of the remaining thick ice is situated near the Fram Strait. Wind and ocean currents tend to push ice out of the Arctic Ocean and through the Fram. Ice tends to then be funneled down along the coast of Greenland and on into the North Atlantic where it melts. So the fact that a big chunk of the already greatly reduced remaining thick ice now sits on the edge of the sea ice version of Niagra Falls is not a good sign.

La Nina Years Tend to Push More Heat Toward the Poles

It is notoriously difficult to accurately forecast sea ice melt and refreeze trends in the various seasonal measures for any given individual year. And even many of the top sea ice experts have had a devil of a time forecasting the behavior of sea ice during recent years. However, one thing remains quite clear — the long term trend for sea ice in the Arctic is one of rapid decline.

(Arctic sea ice ‘Death Spiral’ by Andy Lee Robinson. Image source: Haveland.)

We are now entering a situation where one very warm winter followed by one warmer than normal summer could push Arctic sea ice values to near the zero mark. A situation that could effectively set off a blue ocean event in the near future. A number of prominent sea ice experts have predicted that it’s likely that such a state will be achieved rather soon — by the early 2030s under current trends. Others point toward nearer-term loss potentials. But there is practically no-one now saying, as was often stated during the early 2010s, that a blue ocean event could hold off until the early 2050s.

All that said, the trajectory going into 2017 for the Arctic at present doesn’t look very good. Both sea ice extent and volume are now at or well below the previous low marks for this time of year. Remaining thick ice positioned near the Fram Strait generates a physical disadvantage to the ice in general. In addition, NOAA has announced that La Nina conditions are now present in the Equatorial Pacific. And La Nina events tend to push more ocean and atmospheric heat toward the poles — particularly toward the Arctic.

Links/Notes/Disclaimer:

Note: This article is written as a follow-on to the previous blog post — For The Arctic Ocean Above 80 North, It’s Still Summer in November — and they should be read together for context.

Disclaimer: I asked PhD student Zachary Labe to make a general comment on sea ice trends, to which he generously provided his particular take on the Arctic. I have also made my own best-shot science and observation-based analysis of the situation given current trends. Because of the fact that the present situation is new and evolving, some of my statements may well pass outside the bounds of currently accepted science. The fact that Labe commented in this post does not, in this case, mean that he agrees fully or in part with my particular initial rough analysis of the subject.

Zack Labe’s Sea Ice Figures

NSIDC

Permafrost and Arctic Sea Ice — Climate Canaries in the Coal Mine

Increasing Fall-Winter Energy Loss From the Arctic Ocean and its Role in Arctic Temperature Amplification

Earth Nullschool

Arctic Sea Ice Graphs

PIOMAS

U.S. Navy ARCc Model Sea Ice Thickness

Haveland

NOAA

Hat tip to Andy Lee Robinson

Hat tip to Cate

Winter Arctic methane emissions higher than expected

"Virtually all the climate models assume there's no or very little emission of methane when the ground is frozen," Oechel said. "That assumption is incorrect."

Methane Emissions in Arctic Cold Season Higher Than Expected

Half of Alaska's methane emissions occur in winter -- mostly during times when soil temperatures are poised near freezing. Credit: NASA/JPL-Caltech 

NASA,

21 December, 2015

The amount of methane gas escaping from the ground during the long cold period in the Arctic each year and entering Earth's atmosphere is likely much higher than estimated by current carbon cycle models, concludes a major new study led by San Diego State University and including scientists from NASA's Jet Propulsion Laboratory, Pasadena, California.

After Four Years, CARVE Makes Its Last Arctic Flight

On Nov. 12 of this year, NASA's Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) completed its final aircraft flight. During its four-year campaign, CARVE accumulated more than 1,000 science flight hours of measurements over Alaska, collecting data on important greenhouse gases during seven to eight months of each year.

The permafrost (perennially frozen) and peat soils of Arctic and boreal (northern region) ecosystems are the single largest reservoir of terrestrial carbon, containing twice as much carbon as is currently present in the atmosphere. As Arctic soils thaw and fires proliferate due to global warming, accentuated at high latitudes, the risk that the carbon will be released to the atmosphere continues to increase. CARVE collected detailed measurements of carbon dioxide, carbon monoxide and methane over every Alaskan Arctic and boreal ecosystem.

The end of such a long mission is bittersweet, says Principal Investigator Charles Miller of NASA's Jet Propulsion Laboratory, Pasadena, California. "We've made lots of friends in Alaska. After four years, it's almost like another university education." The team has been making preliminary data available after each year's campaign, and now, Miller says, "We have a few months to make sure we've got all data calibrated, analyzed and quality controlled to the best of our ability, and then it will go to the terrestrial ecology Distributed Active Archive Center at Oak Ridge [National Laboratory, Tennessee]." In spring 2016, all four years of data and the team's supporting analysis and modeling results will be posted and freely available to interested users.

The study included a team comprising ecologists Walter Oechel (SDSU and Open University, Milton Keynes, United Kingdom) and Donatella Zona (SDSU and the University of Sheffield, United Kingdom) and scientists from JPL; Harvard University, Cambridge, Massachusetts; the National Oceanic and Atmospheric Administration, Boulder, Colorado; and the University of Montana, Missoula. The team found that far more methane is escaping from Arctic tundra during the cold months when the soil surface is frozen (generally from September through May), and from upland tundra, than prevailing assumptions and carbon cycle models previously assumed. In fact, they found that at least half of the annual methane emissions occur in the cold months, and that drier, upland tundra can be a larger emitter of methane than wet tundra. The findings challenge critical assumptions in current global climate models. The results are published this week in the Proceedings of the National Academy of Sciences.

Methane is a potent greenhouse gas that contributes to atmospheric warming, and is approximately 25 times more potent per molecule than carbon dioxide over a 100-year period. Methane trapped in the Arctic tundra comes primarily from microbial decomposition of organic matter in soil that thaws seasonally. This methane naturally seeps out of the soil over the course of the year, but scientists worry that climate change could lead to the release of even larger emissions from organic matter that is currently stabilized in a deep, frozen soil layer called permafrost.

Over the past several decades, scientists have used specialized instruments to accurately measure methane emissions in the Arctic and incorporated those results into global climate models. However, almost all of these measurements have been obtained during the Arctic's short summer. The region's long, brutal cold period, which accounts for between 70 and 80 percent of the year, has been largely "overlooked and ignored," according to Oechel. Most researchers, he said, figured that because the ground is frozen solid during the cold months, methane emissions practically shut down for the winter.

"Virtually all the climate models assume there's no or very little emission of methane when the ground is frozen," Oechel said. "That assumption is incorrect."

The water trapped in the soil doesn't freeze completely even below 32 degrees Fahrenheit (0 degrees Celsius), he explained. The top layer of the ground, known as the active layer, thaws in the summer and refreezes in the winter, and it experiences a kind of sandwiching effect as it freezes. When temperatures are right around 32 degrees Fahrenheit -- the so-called "zero curtain" -- the top and bottom of the active layer begin to freeze, while the middle remains insulated. Microorganisms in this unfrozen middle layer continue to break down organic matter and emit methane many months into the Arctic's cold period each year.

Just how much methane is emitted during the Arctic winter? To find out, Oechel and Zona oversaw the upgrade of five sampling towers to allow them to operate continuously year-round above the Arctic Circle in Alaska. The researchers recorded methane emissions from these sites over two summer-fall-winter cycles between June 2013 and January 2015. The arduous task required highly specialized instruments that had to operate continuously and autonomously through extreme cold for months at a time. They developed a de-icing system that eliminated biases in the measurement and that was only activated when needed to maintain operation of the instruments down to minus 40 degrees Fahrenheit (minus 40 degrees Celsius).

After analyzing the data, the research team found a major portion of methane emissions during the cold season were observed when temperatures hovered near the zero curtain.

"This is extremely relevant for the Arctic ecosystem, as the zero curtain period continues from September until the end of December, lasting as long or longer than the entire summer season," said Zona, the study's first author. "These results are opposite of what modelers have been assuming, which is that the majority of the methane emissions occur during the warm summer months while the cold-season methane contribution is nearly zero."

Surprisingly, the researchers also found that during the cold seasons they studied, the relative methane emissions were higher at the drier, upland tundra sites than at wetland sites, contradicting yet another longstanding assumption about Arctic methane emissions. Upland tundra was previously assumed to be a negligible contributor of methane, Zona said, adding that the freezing of the surface inhibits methane oxidation, resulting in significant net methane emissions during the fall and winter. Plants act like chimneys, facilitating the escape through the frozen layer to the atmosphere. The highest annual emissions were observed in the upland site in the foothills of the Brooks Range, where warm soils and a deep active layer resulted in high rates of methane production.

To complement and verify the on-the-ground study, the University of Montana's John Kimball and his team used microwave sensor measurements from the AMSR-E instrument aboard NASA's Aqua satellite to develop regional maps of surface water cover, including the timing, extent and duration of seasonal flooding and drying of the region's wetlands.

"We were able to use the satellite data to show that the upland tundra areas that appear to be the larger methane sources from the on-the-ground instruments, account for more than half of all of the tundra in Alaska," Kimball said.

Finally, to test whether their site-specific sampling was representative of methane emissions across the Arctic, the researchers compared their results to measurements recorded during aircraft flights over the region made by NASA's Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE).

"CARVE flights were designed to cover as much of the year as feasible," said CARVE Principal Investigator Charles Miller of JPL. "It was a challenging undertaking, involving hundreds of hours of flying in difficult conditions."

The data from the SDSU sites were well aligned with the larger-scale aircraft measurements, Zona said.

"CARVE aircraft measurements of atmospheric methane show that large areas of Arctic tundra and boreal forest continue to emit methane to the atmosphere at high rates, long after the surface soil freezes," said Róisín Commane of Harvard University, who helped acquire and analyze the aircraft data.

Oechel and Zona stressed the importance for modelers to have good baseline data on methane emissions and to adjust their models to account for Arctic cold-season methane emissions as well as the contributions of non-wetland areas, including upland tundra.

"It is now time to work more closely with climate modelers and assure these observations are used to improve model predictions, and refine our prediction of the global methane budget," Zona said.

It is particularly important, Oechel added, for models to get methane output right because the gas is a major driver of atmospheric warming. "If you don't have the mechanisms right, you won't be able to make predictions into the future based on anticipated climate conditions," he said.

Steven Wofsy of Harvard University added, "Now that we know how important the winter is to the methane budget, we are working to determine the long-term trends in greenhouse emissions from tundra and their sensitivity to winter warming."

This research has been funded by the National Science Foundation, NASA and the Department of Energy.

SDSU; JPL; Harvard University; the University of Montana; the University of Sheffield; the National Research Council (CNR) of Italy; the University of Helsinki; the University of Colorado, Boulder; Atmospheric and Environmental Research, Lexington, Massachusetts; the University of Alaska, Fairbanks; Dalhousie University, Halifax, Nova Scotia, Canada; NOAA; and Open University all contributed to the study.

NASA uses the vantage point of space to increase our understanding of our home planet, improve lives and safeguard our future. NASA develops new ways to observe and study Earth's interconnected natural systems with long-term data records. The agency freely shares this unique knowledge and works with institutions around the world to gain new insights into how our planet is changing.

More information on CARVE:

http://science.nasa.gov/missions/carve/

More information about NASA's Earth science activities:

http://www.nasa.gov/earth

Media Contact

Alan Buis 
Jet Propulsion Laboratory, Pasadena, Calif. 
818-354-0474
Alan.buis@jpl.nasa.gov

Beth Downing Chee
San Diego State University, San Diego
619-594-4563
bchee@mail.sdsu.edu 

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