E. Osborne1, J. Richter-Menge2, M. Jeffries3
1National Oceanic and Atmospheric Administration, Arctic Research Program, Silver Spring, MD, USA
2University of Alaska Fairbanks, Institute of Northern Engineering, Fairbanks, AK, USA
3Cold Regions Research and Engineering Laboratory of the Engineer Research and Development Center, U.S. Army Corps of Engineers, Hanover, NH, USA
In its 13th year, NOAA's Arctic Report Card (www.arctic.noaa.gov/Report-Card/) reflects on a range of land, ice, and ocean observations made throughout the Arctic during the 2018 calendar year. A series of 14 essays written by more than 80 scientists from 12 countries are included in the 2018 Arctic Report Card. As in previous years, this update highlights the changes that continue to occur in, and among, the physical and biological components of the Arctic environmental system.
In 2018, surface air temperatures in the Arctic continued to warm at roughly twice the rate relative to the rest of the globe, a phenomenon that has been termed "Arctic Amplification." The year 2018 was the second warmest year on record in the Arctic since 1900 (after 2016), at +1.7° C relative to the long-term average (1981-2010). Arctic air temperatures for the past five years (2014-18) have exceeded all previous records since 1900. Growing atmospheric warmth in the Arctic results in a sluggish and unusually wavy jet-stream that coincided with abnormal weather events in both the Arctic and mid-latitudes. Notable extreme weather events coincident with deep waves in the jet-stream include the heat wave at the North Pole in autumn 2017, a swarm of severe winter storms in the eastern United States in 2018, and the extreme cold outbreak in Europe in March 2018 known as "the Beast from the East."
Continued warming of Arctic atmospheric temperatures in 2018 is an indicator of both regional and global climate change and a driver of broad Arctic environmental change. In the terrestrial system, atmospheric warming continued to drive broad, long-term trends in declining terrestrial snow cover, melting of the Greenland Ice Sheet and lake ice, increasing summertime Arctic river discharge, and the expansion and greening of Arctic tundra vegetation. Despite the growth of vegetation available for grazing land animals, herd populations of caribou and wild reindeer across the Arctic tundra have declined by nearly 50% over the last two decades.
As a result of atmosphere and ocean warming, the Arctic is no longer returning to the extensively frozen region of recent past decades. In 2018 Arctic sea ice remained younger, thinner, and covered less area than in the past. The wintertime maximum sea ice extent measured in March of 2018 was the second lowest in the 39-year record, following only 2017. For the satellite record (1979-present), the 12 lowest sea ice extents have occurred in the last 12 years. The disappearance of the older and thicker classes of sea ice are leaving an ice pack that is more vulnerable to melting in the summer, and liable to move unpredictably. When scientists began measuring Arctic ice thickness in 1985, 16% of the ice pack was very old (i.e., multiyear) ice. In 2018, old ice constituted less than 1% of the ice pack, meaning that very old Arctic ice has declined by 95% in the last 33 years. The pace and extent of the changes to summer sea ice cover, along with regional air temperatures and advection of waters from the Pacific and Atlantic oceans, are linked to the spatial patterns of late summer sea surface temperature. August mean sea surface temperatures in 2018 show statistically significant warming trends for 1982-2018 in most regions of the Arctic Ocean that are ice-free in August.
Later sea ice freeze-up and earlier ice break-up also have important implications for the extent and thickness of coastal landfast ice. This seasonal form of ice hardens and fastens to the coast. The direct connection to the coast makes landfast ice the most accessible form of sea ice and the one most often encountered by people. This ice platform is used for hunting and travel and plays a critical role buffering the coastal communities against the erosive action of strong winter storms. Pan-Arctic observations suggest a long-term decline in landfast ice since measurements began in the 1970s. Broad observations of Chukchi-bounded landfast ice along the North Slope of Alaska suggest an extent that is half as far offshore in the 2000s compared to the 1970s. A 16-year time series of landfast ice thickness within this region near Utqiaġvik (formerly Barrow) reveal a 30-cm thinning of ice since the year 2000.
One of the more remarkable features of Arctic sea ice in 2018 was the dearth of ice in the Bering Sea, which was at a record low extent for virtually the entire 2017/18 ice season. The reduced sea ice coverage and early break-up of ice had a profound effect on ocean primary productivity in 2018, particularly in the Bering Sea region where productivity levels were sometimes 500% higher than normal levels. Warming Arctic Ocean conditions are also coinciding with an expansion of harmful algae species responsible for toxic algal blooms in the Arctic Ocean. Considerable concentrations of algal toxins have been found in the tissues of Arctic clams, seals, walrus, and whales and other marine organisms. Impacts of the anticipated continued expansion of harmful algal blooms will be significant in a region where traditional monitoring programs for toxins in shellfish, fish, or other food sources are not feasible due to remote and expansive coastlines.
Another emerging threat of marine microplastics is taking form in the Arctic. A recent global survey of marine microplastics revealed that concentrations in the remote Arctic Ocean are higher than all other ocean basins in the world. Particularly high levels of microplastics are found in the Greenland and Barents seas in the northeastern Atlantic sector of the Arctic and point to the transportation and delivery of marine debris through global thermohaline ocean circulation. The handful of existing monitoring programs in the Arctic show microplastics contamination has increased over the last decade and pose a threat to seabirds and marine life that can become entangled or ingest debris.
The collective results reported in the 2018 Arctic Report Card show that the effects of persistent Arctic warming continue to mount. Continued warming of the Arctic atmosphere and ocean are driving broad change in the environmental system in predicted and, also, unexpected ways. New and rapidly emerging threats are taking form and highlighting the level of uncertainty in the breadth of environmental change that is to come. Long-term monitoring programs are critical to our understanding of baseline conditions and the magnitude and frequency of the changes that are being delivered to the Arctic. Such understanding is central to the livelihood of communities that call the Arctic home as well as the rest of the globe which is already experiencing the changes and implications of a warming and melting Arctic.
Financial support for the Arctic Report Card is provided by the Arctic Research Program in the NOAA Climate Program Office. Preparation of Arctic Report Card 2018 was directed by the NOAA Arctic Research Program, with editorial assistance by researchers from the University of Alaska Fairbanks (via research sponsored by the Cooperative Institute for Alaska Research with funds from the NOAA Administration under cooperative agreement NA13OAR4320056 with the University of Alaska) and in kind support from the Office of Naval Research and the Cold Regions Research and Engineering Laboratory of the Engineer Research and Development Center, U.S. Army Corps of Engineers. The 14 contributions to Arctic Report Card 2018, representing the collective effort of an international team of 81 researchers in 12 countries, are based on published and ongoing scientific research. Independent peer review of the scientific content of Arctic Report Card 2018 was facilitated by the Arctic Monitoring and Assessment (AMAP) Program of the Arctic Council.
December 3, 2018