The Changes in the Arctic are Irreversible: NOAA
Return to previous Arctic conditions is unlikely
Record temperatures across Canadian Arctic and Greenland, a reduced summer sea ice cover, record snow cover decreases and links to some Northern Hemisphere weather support this conclusion
NOAA.gov, Oct. 21, 2010
J. Overland1, M. Wang2, and J. Walsh 3
1NOAA, Pacific Marine Environmental Laboratory, Seattle, WA 2Joint Institute for the Study of the Atmosphere and Ocean, University of Washington, Seattle, WA 3International Arctic Research Center, Fairbanks, AK
While 2009 showed a slowdown in the rate of annual air temperature increases in the Arctic, the first half of 2010 shows a near record pace with monthly anomalies of over 4°C in northern Canada. There continues to be significant excess heat storage in the Arctic Ocean at the end of summer due to continued near-record sea ice loss. There is evidence that the effect of higher air temperatures in the lower Arctic atmosphere in fall is contributing to changes in the atmospheric circulation in both the Arctic and northern mid-latitudes. Winter 2009-2010 showed a new connectivity between mid-latitude extreme cold and snowy weather events and changes in the wind patterns of the Arctic; the so-called Warm Arctic-Cold Continents pattern.
The annual mean air temperature for 2009 over Arctic land areas was cooler than in recent years, although the average temperature for the last decade remained the warmest in the record beginning in 1900 (Fig. A.1). The 2009 average was dominated by very cold temperatures in Eurasia in February (the coldest of the decade) and December, while the remainder of the Arctic remained warm (Fig. A.2). The spatial distribution of annual temperature anomalies for 2009 has a pattern with values greater than 2.0°C throughout the Arctic, relative to a 1968–96 reference pefriod (Fig. A.3). These anomalies show the major feature of current Arctic conditions, where there is a factor of two (or more) amplification of air temperature relative to lower latitudes.
Sea Ice Cover
D. Perovich1, W. Meier2, J. Maslanik3, and J. Richter-Menge1
1 ERDC – CRREL, 72 Lyme Road, Hanover NH 03755
2 National Snow and Ice Data Center, U of Colorado, Boulder CO 80309
3 Aerospace Engineering Sciences, U of Colorado, Boulder CO 80309
September minimum sea ice extent is third lowest recorded
Loss of thick multiyear ice in Beaufort Sea during summer
Sea ice extent
Sea ice extent is the primary parameter for summarizing the state of the Arctic sea ice cover. Microwave satellites have routinely and accurately monitored the extent since 1979. There are two periods that define the annual cycle and thus are of particular interest: March, at the end of winter when the ice is at its maximum extent, and September, when it reaches its annual minimum. Maps of ice coverage in March 2010 and September 2010 are presented in Figure I1, with the magenta line denoting the median ice extent for the period 1979–2000.
On September 19, 2010 sea ice extent reached a minimum for the year of 4.6 million km2. The 2010 minimum is the third-lowest recorded since 1979, surpassed only by 2008 and the record low in 2007. Overall, the 2010 minimum was 31% (2.1 million km2) lower than the 1979-2000 average. The last four summers have experienced the four lowest minimums in the satellite record, and eight of the ten lowest minimums have occurred during the last decade. Surface air temperatures through the 2010 summer were warmer than normal throughout the Arctic, though less extreme than in 2007. A strong atmospheric circulation pattern set up during June helped push the ice edge away from the coast. However, the pattern did not persist through the summer as it did in 2007 (see the Atmosphere Section for more details).
The March 2010 ice extent was 15.1 million km2, about 4% less that the 1979–2000 average of 15.8 million km2. Winter 2010 was characterized by a very strong atmospheric circulation pattern that led to warmer than normal temperatures. The yearly maximum sea ice extent occurred on March 31. This was the latest date for the maximum ice extent observed in the 30 year satellite record and was due primarily to late ice growth in the Bering Sea, Barents Sea, and the Sea of Okhotsk.
The time series of the anomalies in sea ice extent in March and September for the period 1979–2009 are plotted in Figure I2. The anomalies are computed with respect to the average from 1979 to 2000. The large interannual variability in September ice extent is evident. Both winter and summer ice extent exhibit a negative trend, with values of -2.7 % per decade for March and -11.6% per decade for September over the period 1979-2010.
A. Proshutinsky1, M.-L. Timmermans2, I. Ashik3, A. Beszczynska-Moeller4, E. Carmack5, I. Frolov3, R. Krishfield1, F. McLaughlin5, J. Morison6, I. Polyakov7, K. Shimada8, V. Sokolov3, M. Steele6, J. Toole1, and R. Woodgate6
1Woods Hole Oceanographic Institute, Woods Hole, MA
2Yale University, New Haven, Connecticut
3Arctic and Antarctic Research Institute, St. Petersburg, Russia
4Alfred Wegener Institute, Germany
5Institute of Ocean Sciences, Sidney, Canada
6Polar Science Center, University of Washington, Seattle, Washington
7International Arctic Research Center, Fairbanks, Alaska
8Institute of Observational Research for Global Change, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan
In 2009 the annual wind-driven Arctic Ocean circulation regime was cyclonic for the first time since 1997. This regime significantly influenced the characteristics of the sea ice cover and ocean: maximum upper ocean temperatures in summer 2009 continued to decline relative to the historical extreme warm conditions observed in summer 2007; surface-layer waters in the Arctic Ocean in 2009 remained much fresher than in the 1970s and were comparable to 2008 conditions; and the sea level along the Siberian coastline significantly decreased relative to 2008. An interesting change in ocean geochemistry was observed in the Canada Basin. The combination of an increase in the amount of melt water from the sea ice cover and CO2 uptake (acidification) in the ocean caused the surface waters of the Canada Basin to become corrosive to calcifying organisms.
In 2009, the annual wind-driven ocean circulation regime can be characterized as cyclonic (counterclockwise), with a Beaufort Gyre that is significantly reduced in strength and a Transpolar drift that is effectively nonexistent (Fig. O.1). This is the first time that an annual cyclonic circulation regime has been observed in the Arctic since 1997. The anticyclonic circulation regime that persisted through 2008 lasted at least 12 years instead of the typical 5–8 year pattern [as reported in Proshutinsky and Johnson (1997), who analyzed statistics of Arctic circulation regimes between 1948 and 1989]. The climatological seasonal cycle of the Arctic has anticyclonic ice and ocean circulation prevailing in winter and cyclonic circulation in summer. Since 2007, this seasonality has changed dramatically. In 2007, both summer and winter circulations were very strongly anticyclonic (Fig. O.1, top panels) and resulted in the unprecedented reduction of the Arctic Ocean summer sea ice cover. In 2008, the winter circulation was anticyclonic but the summer circulation was unusual with a well-pronounced Beaufort Gyre and a cyclonic circulation cell north of the Laptev Sea (Fig. O.1, middle panels). In 2009 (Fig. O.1, bottom panels), the circulation reversed relative to climatology in both winter and summer: it was anticyclonic in summer (instead of cyclonic) and cyclonic in winter (instead of anticyclonic). These wind-driven conditions significantly influenced the characteristics of the sea ice cover, oceanic currents, ocean freshwater and heat content observed during 2007–09.
Water temperature and salinity
Maximum upper ocean temperatures in summer 2009 continued to decline since the historical extreme in summer 2007 (Fig. O.2). This tendency is strongly linked to changes in the characteristics (e.g., pace and location) of the summer sea ice retreat and their effect on local atmospheric warming (Steele et al. 2010, manuscript submitted to J. Geophys. Res.). Surface warming and sea ice reduction in the Canada Basin has also been accompanied by the widespread appearance of a near-surface temperature maximum at 25–35 m depth due to penetrating solar radiation (Jackson et al. 2010). As described in the Arctic atmosphere section, the heat accumulated in the surface and near-surface layers of the ocean can be released back into the atmosphere in the fall—a cycle that is likely to influence sea ice conditions in the future.
Surface-layer waters in the Arctic Ocean in 2009 remained much fresher than in the 1970s (Timokhov and Tanis 1997, 1998). In the Beaufort Gyre, freshwater content in 2009 (Fig. O.3) was comparable to the 2008 freshwater conditions, with the exception of the southwest corner of the Canada Basin. In this region, the freshwater accumulation was increased relative to 2008 by approximately 0.4 km3 under enhanced Ekman pumping and sea ice melt in this region. In total, during 2003–09 the Beaufort Gyre (Proshutinsky et al. 2009) has accumulated approximately 5000 km3 of freshwater (from 17 300 km3 in 2003 to 22 300 km3 in 2009), which is 5800 km3 larger than climatology of the 1970s (Timokhov and Tanis 1997, 1998).
Figure O.6 shows sea level (SL) time series from nine coastal stations in the Siberian Seas, having representative records for the period of 1954–2009 (Arctic and Antarctic Research Institute data archives). In 2009, the SL along the Siberian coastline has significantly decreased relative to 2008. This caused a slight reduction in the estimated rate of SL rise for the nine stations over the period, to 2.57 ± 0.45 mm yr−1 (after correction for glacial isostatic adjustment, GIA). The changing SL rise tendency may be due to the substantial change in the wind-driven ocean circulation regime (less anticyclonic, as described in section 5c1) and/or due to steric effects associated with the reduction of surface ocean warming and freshening rates (section on Water temperature and salinity, above). Ocean cooling and salinification both result in sea level decrease.
J. Richter-Menge, Topic Editor
ERDC-Cold Regions Research and Engineering Laboratory, Hanover, NH
Observations of land-based changes in the Arctic cover a wide spectrum, including variations and trends in vegetation, permafrost, river discharge, snow cover, and mountain glaciers and ice caps. In general, these observations present further evidence of the impact of a general, Arctic-wide warming trend that is accompanied by high variability from year to year and region to region. They also illustrate the connectivity between various elements of the Arctic system, with conditions being linked to atmospheric circulation patterns, sea ice conditions, and ocean surface temperatures.
A combination of low winter snow accumulation and warm spring temperatures created a new record low spring snow cover duration over the Arctic in 2010, since satellite observations began in 1966.
Glaciers and ice caps in Arctic Canada are continuing to lose mass at a rate that has been increasing since 1987, reflecting a trend towards warmer summer air temperatures and longer melt seasons.
Observations show a general increase in permafrost temperatures during the last several decades in Alaska, northwest Canada, Siberia and Northern Europe, with a significant acceleration in the warming of permafrost at many Arctic coastal locations during the last five years.
The greatest changes in vegetation are occurring in the High Arctic of Canada and West Greenland and Northern Alaska, where increases in greening of up to 15% have been observed from 1982 to 2008.
In the Eurasian river drainage basins, the correlation between increased river discharge and decreased summer minimum sea ice extent (over the period 1979-2008) is greater than the correlation between precipitation and runoff, suggesting that both rivers and sea ice were responding to changes in large-scale hemispheric climate patterns.
J. E. Box1, J. Cappelen2, D. Decker1, X. Fettweis3,6, T. Mote4, M. Tedesco5 and R. S. W. van de Wal6
1Byrd Polar Research Center, The Ohio State University, Columbus, Ohio
2Danish Meteorological Institute, Copenhagen, Denmark
3Department of Geography, University of Liège, Liège, Belgium
4Department of Geography, University of Georgia, Atlanta, Georgia
5Department of Earth and Atmospheric Sciences, City College of New York, New York, New York
6Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, The Netherlands
Greenland climate in 2010 is marked by record-setting high air temperatures, ice loss by melting, and marine-terminating glacier area loss. Summer seasonal average (June-August) air temperatures around Greenland were 0.6 to 2.4°C above the 1971-2000 baseline and were highest in the west. A combination of a warm and dry 2009-2010 winter and the very warm summer resulted in the highest melt rate since at least 1958 and an area and duration of ice sheet melting that was above any previous year on record since at least 1978. The largest recorded glacier area loss observed in Greenland occurred this summer at Petermann Glacier, where 290 km2 of ice broke away. The rate of area loss in marine-terminating glaciers this year (419 km2) was 3.4 times that of the previous 8 years, when regular observations are available. There is now clear evidence that the ice area loss rate of the past decade (averaging 120 km2/year) is greater than loss rates pre-2000.
Coastal surface temperatures
A clear pattern of exceptional and record-setting warm air temperatures is evident at long-term meteorological stations around Greenland (Table GL1). For instance:
Nuuk (64.2°N along Greenland's west coast): Year 2010 summer, spring, and winter 2009/2010 were the warmest on record since record keeping began in 1873.
Aasiaat (69.0°N along Greenland's west coast): It was the warmest month of May and August, and the warmest winter, spring, 2nd warmest summer and the warmest year (July 2009-August 2010) since record keeping began in 1951.
Narsarssuaq (61.2°N in southern Greenland): It was the warmest month of May, and the warmest winter, spring and the warmest year (July 2009-August 2010) since record keeping began in 1951.
Thule AFB, Pituffik (76.5°N along Greenland's west coast): It was the warmest spring (March-May) on record, which began in 1961.
Michael J. Gill, Topic Editor
Chair, Circumpolar Biodiversity Monitoring Program, Environment Canada, Whitehorse, Yukon CA
The contribution of Arctic wildlife to global biodiversity is substantial. The region supports globally significant populations of birds, mammals and fish. For example, over half of the world's shorebirds and 80% of the global goose population breed in Arctic and sub-Arctic regions. Many of these populations experience natural and often dramatic cycles in abundance, switching from periods of growth and decline. Dramatic changes (e.g., sea-ice loss) in the Arctic's ecosystems have occurred, are predicted to continue over the next century, and may disrupt these natural cycles. Changes in physical attributes of the Arctic (e.g. increasing air temperatures, decreasing sea ice extent) are expected to result in winners and losers. Arctic species that have adapted to these extreme environments are expected to be displaced by the encroachment of more southerly (sub-Arctic) species and ecosystems. Understanding how the Arctic's living resources are responding to these changes is essential in order to develop effective conservation and adaptation strategies.
· The biological components of the 2010 Arctic Report Cards highlight the inherently fluctuating nature of Arctic ecosystems and provide some insight into how Arctic ecosystems and the biodiversity they support are responding to changing environmental conditions. Dramatic declines in many wild caribou and reindeer populations over the past two decades and the dramatic increases in goose populations over the same period appear to be moderating. Barents Sea harvested stocks continue to fluctuate and these changes may be linked to sea temperatures and the associated fluctuations in sea ice cover. The Arctic Species Trend Index, released in 2010 and drawing on 965 populations of 306 Arctic and sub-Arctic vertebrate species across the Arctic, has been relatively stable since 1970. However, there are significant variations between groups and species, and geographic areas. Populations of vertebrate high arctic species declined 26% between 1970 and 2004. Low and sub-Arctic species have fared better over this time period: the low Arctic species index, largely dominated by marine species, has experienced increasing abundance (although the result is largely biased by pelagic data from the Bering Sea), while the sub-Arctic index (reflecting mostly terrestrial and freshwater species) has declined since the mid-1980s, resulting in no overall change over the 34 year period.
These observed trends are largely consistent with current predictions regarding the response of Arctic wildlife to changing environmental conditions in the Arctic, caused by both natural and human-caused change. Given the predicted dramatic changes in the Arctic over the next century (e.g. from climate change), it is becoming increasingly important to invest in improved monitoring in this remote area to understand how these systems are changing and thereby facilitate more effective and timely conservation and adaptation actions.