M. O. Jeffries1, J. Richter-Menge2, J. E. Overland3
1Office of Naval Research, Arlington, VA, USA
2U.S. Army Corps of Engineers, Cold Regions Research and Engineering Laboratory, Hanover, NH, USA
3National Oceanic and Atmospheric Administration, Pacific Marine Environmental Laboratory, Seattle, WA, USA
The Arctic Report Card (www.arctic.noaa.gov/Report-Card/) considers a range of environmental observations throughout the Arctic, and is updated annually. As in previous years, the 2015 update to the Arctic Report Card highlights the changes that continue to occur in both the physical and biological components of the Arctic environmental system.
The average annual surface air temperature anomaly (+1.3°C relative to the 1981-2010 baseline) over land north of 60°N between October 2014 and September 2015 was the highest in the observational record beginning in 1900. This represents a 2.9°C increase since the beginning of the 20th Century. Average air temperature anomalies in all seasons between October 2014 and September 2015 were generally positive throughout the Arctic, with extensive regions exceeding +3°C relative to the 1981-2010 baseline. Strong connections between the Arctic and mid-latitude regions occurred (1) from November 2014 through June 2015, causing anomalously warm conditions in the Pacific Arctic region due to southerly air flow into and across Alaska, and (2) from February through April 2015, causing anomalously cold conditions from north-eastern North America to southwest Greenland due to northerly air flow.
In 2014, the most recent year with a complete data set, the combined discharge of the eight largest Arctic rivers (2487 km3 from the Pechora, S. Dvina, Ob', Yenisey, Lena, Kolyma [Eurasia], Yukon and Mackenzie [North America]) was 10% greater than the average discharge during 1980-1989. Since 1976, discharge of the Eurasian and North American rivers has increased 3.1% and 2.6% per decade, respectively. For the first seven months of 2015, the combined discharge for the six largest Eurasian Arctic rivers shows that peak discharge was 10% greater and five days earlier than the 1980-1989 average for those months.
Arctic snow cover extent (SCE, for land areas north of 60°N) anomalies in May and June 2015 were below the long-term average for 1981-2010, a continuation of consistent early spring snow melt during the past decade. June SCE in both the North American and Eurasian sectors of the Arctic was the 2nd lowest in the satellite record (1967-present). The rate of June SCE reductions since 1979 (the start of the passive microwave satellite era) is 18% per decade. Since 2011, the rate of June snow cover loss has exceeded the rate of September sea ice loss (-13.4% per decade).
Minimum sea ice extent in September 2015 was 29% less than the average for 1981-2010 and the fourth lowest value in the satellite record (1979-2015). Earlier in the year, the lowest ever maximum ice extent in the satellite record was 7% less than the average for 1981-2010. Occurring on 25 February, it was also the second earliest in the record and 15 days earlier than average (12 March). In February and March 2015, the oldest ice (>4 years) and first-year ice made up 3% and 70%, respectively of the pack ice compared to values of 20% and 35%, respectively, in 1985.
Sea ice retreat is believed to be the most pervasive threat to ice-associated marine mammals, including walruses. In the Pacific Arctic, vast walrus herds are now hauling out on land rather than on sea ice as it retreats far to the north over the deep Arctic Ocean. This is raising concern about the energetics of females and young animals that must now make feeding trips from coastal haul-outs to areas of high prey abundance (180 km one-way), rather than utilizing nearby ice edges as they did in the past. Walrus populations are also affected by hunting. In the case of Svalbard in the Atlantic Arctic, a hunting ban from 1952 to 2012 allowed the walrus population to recover even as ocean and air temperatures increased and sea ice and walrus carrying capacity declined.
As sea ice retreat becomes more extensive in summer and previously ice-covered water is exposed to more solar radiation, sea surface temperature (SST) and upper ocean temperatures are increasing throughout much of the Arctic Ocean and adjacent seas. The Chukchi Sea northwest of Alaska and eastern Baffin Bay off west Greenland have the largest warming trends: ~0.5°C per decade since 1982. In August 2015, SST was up to 4°C higher than the 1982-2010 average in eastern Baffin Bay and the Kara Sea north of central Eurasia.
Increasing ocean primary productivity (conversion of CO2 to organic material) is being observed as summer sea ice extent declines. In 2015, there were widespread positive primary productivity anomalies throughout the Arctic Ocean and adjacent ice-affected seas, from 0.7% to 21% above the 2003-2014 average in Hudson Bay and the Barents Sea, respectively. For the period 2003-2015 there are statistically significant primary productivity trends in the eastern (Eurasian) Arctic, Barents Sea, Greenland Sea, and North Atlantic; the steepest trends are in the eastern Arctic (19.26 g C/m2/yr/dec, a 41.9% increase) and the Barents Sea (17.98 g C/m2/yr/dec, a 30.2% increase).
On land, satellite observations since 1982 of peak tundra greenness, a measure of vegetation productivity and strongly correlated with above-ground biomass, show a consistent decline since 2011. In 2014, the most recent year with a complete data set, maximum greenness (MaxNDVI) in the Eurasian Arctic and for the Arctic as a whole was below the 1982-2014 average, while greenness over the entire growing season (TI-NDVI) had the lowest value in the Eurasian record and the second lowest in the North American record. For the entire period of record (1982-2014), linear trends in MaxNDVI continue to show general circumpolar increases in tundra greenness. However, since 1982 the tundra in northwestern Russia, the Yukon Delta region of western Alaska, and the far northern Canadian Arctic Archipelago has become less green (also referred to as "browning"). Linear trends in TI-NDVI for 1982-2014 also show "browning" in these regions.
Ice on land, as represented by the Greenland Ice Sheet, experienced extensive melting again in 2015; melting occurred over more than 50% of the ice sheet for the first time since the exceptional melting of 2012 and exceeded the 1981-2010 average on 50 of 92 days (54%). Melt season duration was as much as 30-40 days longer than average in western, northwestern and northeastern Greenland, but close to or below average elsewhere on the ice sheet. Average albedo in 2015 was below the 2000-2009 average in northwest Greenland and above average in southwest Greenland. Ice mass loss of 186 Gt over the entire ice sheet between April 2014 and April 2015 was 22% below the average mass loss of 238 Gt for 2002-2015, but was 6.4 times higher than the 29 Gt loss of the preceding 2013-2014 season. Between the end of the 2014 melt season and the end of the 2015 melt season, 22 of the 45 widest and fastest-flowing marine-terminating glaciers had retreated, but the advance of 9 relatively wide glaciers resulted in a low annual net area loss of 16.5 km2. This is the lowest annual net area loss in the 16-year period of observations (1999-2015) and 7.7 times lower than the annual average area change trend of -127 km2.
In summary, there are many signals indicating that environmental system components throughout the Arctic continue to be influenced by long-term upward trends in air temperature, modulated by natural variability in regional and seasonal anomalies.
Financial support for the Arctic Report Card is provided by the Arctic Research Program in the NOAA Climate Program Office, and in-kind support is provided by the Office of Naval Research. We thank our respective organizations - the Office of Naval Research, the U.S. Army Corps of Engineers - Cold Regions Research and Engineering Laboratory, and the NOAA Pacific Marine Environmental Laboratory - for their continued support, and the Editorial Advisory Board for its advice and assistance with identifying topics and authors for Indicators and Frostbites essays. The 12 contributions to Arctic Report Card 2015 represent the collective effort of an international team of 72 researchers in 11 countries. Independent peer-review of Arctic Report Card 2015 was facilitated by the Arctic Monitoring and Assessment Program (AMAP) of the Arctic Council.
December 7, 2015