“The trailing indicators in the Arctic are the leading indicators for the rest of us” – Rick Spinrad, Ph.D., NOAA Chief Scientist, Washington, D.C
Tuesday morning, December 15, NOAA issued the 2015 Arctic Report card at the American Geophysical Union Fall Meeting in San Francisco, CA. Now in its 10th year, the peer-reviewed Arctic Report Card provides the latest Arctic observations from an international team of more than 70 scientists in 10 countries about changes in Arctic air and sea temperatures, snow, sea ice, the Greenland ice sheet and vegetation. This year’s report card contains startling findings concerning summer sea ice extent, terrestrial vegetation, ecological changes in the ocean, and pressures facing walrus populations.
See the full video on the 2015 Arctic Report card here.
CHANGES IN SEA ICE AND THEIR IMPLICATIONS
Melting sea ice is a major concern. Not only does sea ice provide habitat for charismatic species such as walruses, seals, and polar bears, but it is a vital part of the physics of climate. Sea ice is lighter in color than ocean water, and because of this, it has a higher reflectivity, what scientists refer to as “albedo.” Higher albedo means more incoming sunlight is reflected back into the atmosphere, with less heat stored. A lower albedo means more energy from sunlight is absorbed, resulting in the storage of heat that results in warming. Think of the difference between wearing a white t-shirt on a hot summer day versus a dark one.
More sea ice means more energy from the sun is reflected back to the atmosphere and less energy stored as heat in the system. Conversely, if we lose sea ice and are left with nothing but the ocean and its very low albedo in the summer, much more of that energy will be absorbed as heat. In 2015, sea ice extent in the Arctic reached its maximum on February 25, 15 days earlier than the average and the earliest on record (1979-present). Minimum sea ice extent was the fourth lowest on record, with 2012 still lowest. The sea ice formation that is present, also tends to be much younger, with twice as much first-year ice than there was 30 years ago. Younger ice is thinner and much more susceptible to melting in the summer. Changes in sea ice alone are having profound effects on the marine ecosystem and sea surface temperatures. Widespread, above average primary productivity was observed in the Bering Sea (21% above the 2003-2015 average), and has increased by 30% since 2003. Warm-water fish species are also moving north and displacing Arctic species. The warmer water and greater food availability create habitat for these fish.
GREENLAND ICE SHEET
The Greenland Ice Sheet, which is over 2 kilometers thick and comprised of over 2,850,000 cubic kilometers of ice, represents a major global change concern. Were the entire ice sheet to melt, global sea level would rise by over 7 to 8 meters. In 2015, melting occurred over 50% of ice sheet, the highest areal extent of melt since 2012 when 90% of the ice sheet was melting. Melt season duration, the time period during the year when the ice sheet is melting, was 30-40 days longer than average in the north, yet at or below the average in the south. This pattern is consistent with extreme jet stream conditions that we have seen in 2015 that result in clear skies in the north, and lowered temperatures and more cloud cover in the south.
“We know what happens in the Arctic, doesn’t stay in the Arctic” – Martin Jeffries Ph.D., Arctic Science Advisor and Program Officer for Arctic and Global Prediction, U.S. Office of Naval Research, Arlington, Virginia
These Arctic connections to lower latitudes are seen elsewhere, such as the anomalously low temperatures in the mid-latitudes of North America in February of 2015—the much publicized “Polar Vortex.” This effect led to warmer temperatures in Alaska and one of the most extreme fire seasons on record.
IMPACTS ON WALRUS POPULATIONS
“The walrus population in the north Pacific has declined by over 50% in the last decade.” – Kit Novacs, Biodiversity Research Program Leader, Norwegian Polar Institute
The loss of sea ice is the single most pervasive threat to ice-associated marine mammals, such as walruses. Walruses are broadly distributed across the Arctic. They are benthic feeders, or bottom feeders who primarily survive on eating benthic invertebrates in foraging areas located in shallow waters. They rely on pack ice for habitat to spawn, give birth, and raise their calves, but also to provide protection from predators. As sea ice disappears or erodes into only areas of deep water, this habitat is lost and walrus populations are threatened. Walruses are increasingly moving on to land, a major and dramatic shift in walrus ecology, “This has not been seen on the scale of living people, but we are seeing it now” remarked Novacs.
CHANGES IN SNOW AND TUNDRA VEGETATION
There has been long-term trend in “greening” in the Arctic tundra that has seen an abrupt reversal in the last two to four years. Greening refers to the conversion of tundra from moss or lichen dominated systems to shrub dominated systems. In satellite imagery, this makes the tundra appear “more green,” hence the term. The recent reversal of this trend interests scientists. “Changes in snow could be affecting vegetation, or perhaps changes in cloudiness or aerosols or even disturbance could be driving changes on the landscape,” said Howard Epstein, an author on the report and Professor at the University of Virginia, “this will be an area of research interest moving forward.”
Changes in vegetation in the tundra result in complex outcomes in the ecosystem. In one sense, shrubs provide insulation to permafrost as shrubs facilitate cooler soil temperatures in the summer. However, shrubs create warmer soil temperatures in the winter. Shrubs also have a lower albedo than the vegetation they are replacing, which overall contributes to more heat storage and greater warming overall.
2015 also provided the second lowest June snow cover extent on land, a continued decrease that dates back to 1979, while river discharge from the great rivers of Eurasia and North America has increased during that time.
“We have passed some critical level that if we have two degree warming globally, we will have a four to five degree warming in the arctic by 2040 or 2050,” remarked Jim Overland, NOAA scientist, “ . . . if mitigation strategies are used the next generation may see an ice free summer, but hopefully a return of ice by the end of the century.”
View the full report: http://www.arctic.noaa.gov/reportcard/