The Arctic Climate System GEOG 4271/5271 Mark C. Serreze Department of Geography University of Colorado, Boulder CO serreze@nsidc.org
Why study the Arctic climate system? The fascinating processes that occur in a cold environment with a highly varied landscape and an extreme seasonal cycle in solar radiation The Arctic s role in the global climate system the Arctic as the Northern Hemisphere heat sink A system now in the midst of rapid change that may have climate impacts extending into middle latitudes The growing economic and strategic importance of the Arctic region (increased shipping, natural resource extraction)
Annual temperature trends, 1960-2011 strongest warming in the Arctic Based on the NASA GISS analysis
End-of-summer sea ice extent is declining at a faster rate than expected from climate model simulations From Stroeve et al., 2012
Emerging impacts Polar bears and other marine mammals Coastal erosion Access to shipping and oil resources (Beaufort and Chukchi seas)
Oil and gas development http://arcticoceanforever.com/the-risks/
http://www.globalchange.gov/publications/reports/scientific-assessments/us-impacts/fullreport/regional-climate-change-impacts/alaska
1) Historical explorations Human migrations by land bridge (Asia to North America) Ship expeditions (1500s onward) -- search for Europe-China trade route; whaling, fishing -- coastal areas mapped in 1700s Late 1700s: earliest scientific observations -- air/ocean temperature -- sea ice from ships -- permafrost temperature Mid-late 1800s: exploration of Greenland, attempts to reach N. Pole (ships stranded in ice; first icebreakers)
2) Systematic observations International Polar Years (IPYs) -- First IPY, 1882-83: 12 Arctic stations established -- Nansen s Fram expedition; ship drifted across Arctic Ocean Iceberg and sea ice monitoring (some regions) began after 1912 1910s, 1920s: Start of aircraft expeditions over Arctic 1930s: Manned stations on Greenland Second IPY, 1932-33: Northern Sea Route navigated 1930s: Rawinsondes first used for routine profiles above land First Russian drifting ice station in 1937: North Pole 1
3) The Modern Era, 1940s onward Network of North American stations (Distant Early Warning line) Russian NP stations 2-31, 1950s-1991 (1-3 always on the ice) -- U.S. has had occasional stations 1957-58: International Geophysical Year -- Antarctic stations established 1979: International Arctic Buoy Network established 1970s: Satellite remote sensing of sea ice became routine 1990s: Deep ice cores (100,000+ years) from Greenland 1990s-present: the era of programmed science (many field programs with acronyms) 2007-2009: Third International Polar Year -- included cruises, 6-8 multidisciplinary monitoring stations ( intensive observatories )
Some famous names and ships Robert Peary The Gjoa The Fram Roald Amundsen Photos courtesy NSIDC
Russian ice station NP-1: 1937-1938
Arctic Ocean buoy (2000)
Arctic buoy locations: October 2010 http://iabp.apl.washington.edu/
IPY legacy: Network of intensive atmospheric observatories International Arctic System for Observing the Atmosphere (IASOA)
Physical Characteristics and Basic Climate Features
Antarctic: An ice sheet surrounded by ocean askjdhf Arctic: Ocean surrounded by land NASA
Physiography of the Arctic lands, showing topography and major river systems [courtesy of R. Lammers, University of New Hampshire, Durham, NH].
Greenland and its ice sheet. The location of GC-Net automatic weather stations in Greenland (+), expedition stations (x), and coastal settlements (o) [from Steffen and Box, 2001, by permission of AGU].
Duration of daylight by day of year and latitude. At the North Pole there is six months of 24-hour daylight and six months of polar darkness. At the Arctic circle there is one day of 24-hour daylight (at the summer solstice) and one day of polar darkness (at the winter solstice). http://en.wikipedia.org/wiki/day_length
Sunset, Toolik Lake Alaska, April 20 2009 Photograph by M. Serreze
Bathymetry of the Arctic Ocean and major geographic features. The deepest depth is over 4000 m. Note the extensive, shallow continental shelves along the Eurasian side. The Arctic Ocean has only limited connection to the world ocean and is sometimes referred to as a Mediterranean type sea. http://www.marinebio.net/marines cience/04benthon/arcocean.htm
The Arctic sea ice cover Typical seasonal range in Arctic sea ice extent, based on AMSR-E data, plots by Univ. Bremen. There is about a factor of two difference between maximum (March) and minimum (September) extent.
Sea ice field for the central Arctic Ocean for 6 July 2001, based on visible-band Moderate Resolution Imaging Spectroradiometer (MODIS) imagery. The horizontal resolution is about 250 m. The image is about 376 km by 226 km. The strip in the middle of the image shows a typical configuration of leads in the sea ice cover. At the top and bottom of the image, cloud cover masks the surface, a pervasive problem in the Arctic with respect to visible and infrared-band systems. Passive microwave sensors like SSM/I have all-weather capability and can monitor sea ice conditions during polar darkness, but at a relatively coarse spatial resolution [courtesy of T. Haran, NSIDC, Boulder, CO].
Sea ice field in the Barents Sea near Franz Josef Land for 6 July 2001, based on visible-band MODIS imagery. The horizontal resolution is about 250 m. The image is about 526 km by 376 km. The scene shows the transition from high ice concentration to open ocean waters (the marginal ice zone). Note the large individual ice floes and polynyas on the righthand side of the image and the ice caps on the islands of Franz Josef Land [courtesy of T. Haran, NSIDC, Boulder, CO].
A view from the ground, near Barrow Alaska, April 2008. Note the fresh snow cover atop the sea ice and the pressure ridges in the background. The level ice is about 1.5 m thick, the ridged ice up to perhaps 5 m [photograph by M. Serreze].
Mean surface salinity (psu) for summer [from Arctic Climatology Project,1998, NSIDC, Boulder CO]. Note the low salinities along coastal areas due to river runoff. Salinities increase towards the Atlantic side.
Mean surface salinity (psu) for winter [from Arctic Climatology Project, 1997, NSIDC, Boulder, CO]. The river runoff signal is not as apparent.
Temperature and salinity profiles for the Beaufort Sea and near the pole. The y-axis is depth in decibars (dbar), which closely approximates depth in meters [courtesy of J. Morison, Polar Science Center, University of Washington, Seattle, WA]. Note the low salinity very near the surface (the fresh surface layer), and the rapid increase in salinity from the surface downwards. This makes the water column stable, which allows sea ice to readily form. Temperatures are highest not at the surface, but at 250-400 m depth. This warm, salty layer at depth represents water imported from the Atlantic Ocean.
Changes in ocean circulation have played a role Major surface (blue) and deep currents (red and orange) of the Arctic Ocean, along with the approximate summer limit if sea ice. Courtesy Woods Hole Oceanographic Institution
Distribution of Arctic polar desert (dark shading) and approximate southern limit of tundra (bold line) [adapted from Charlier, 1969, also see Webber, 1974, courtesy of N. Saliman, NSIDC, Boulder, CO].
Polar Desert, Ellesmere Island Photograph by C. Allen
Northern Hemisphere permafrost distribution, from the International Permafrost Association Circum-Arctic Map of Permafrost and Ice Conditions. Permafrost can be continuous, discontinuous, sporadic or isolated. The existence of permafrost is defined on the basis of temperature only (ground where the temperature is below freezing for at least two years) and may or may not contain significant ground ice. http://nsidc.org/fgdc/maps/ipa_browse.html
Average number of weeks of snow cover over the Northern Hemisphere, based on the NSIDC blended weekly product [courtesy of M.J. Brodzik, NSIDC, Boulder, CO].
Maximum snow depth (mm) over Eurasia compiled from Russian sources [courtesy of H. Ye, California State University, Los Angeles, CA]. Snow depths are in general quite modest.
Distribution of snow depth (mm) over the central Arctic Ocean for April from NP data [from Colony et al., 1998, by permission of Cambridge University Press]. Note the long tail of the distribution associated with snow drifts and hollows.
An extreme outlier Photograph by M. Serreze
Sastrugi Photograph by K. Elder
Mean annual precipitation (mm) based on available biasadjusted data sources. Contour intervals are 100 mm (solid, for amounts up to 600 mm) and 200 mm (dotted, for amounts 800 mm and greater) [by the authors]. Parts of the Arctic qualify as desert. Other parts are rather moist.
Mean surface air temperature ( C) for January, April, July and October [adapted and updated from Rigor et al., 2000, by permission of AMS]. Due to melting ice, July temperature over the Arctic Ocean hovers about the freezing point.
MODIS Composite for 11 July 2010 The Arctic is a cloudy place! http://rapidfire.sci.gsfc.nasa.gov/subsets/?mosaic=arctic
Typical steel grey Arctic sky - Svalbard Photograph by M. Serreze
Mean annual cycle of cloud cover (total cloud and low cloud, in %) for the central Arctic Ocean based on COADS data through 1995 [by the authors]. Note the sharp rise between April and May, linked to increase in low-level stratus. The central Arctic Ocean is a very cloudy place in summer.
Mean annual cycle of cloud cover (total cloud and low cloud, in %) for the Atlantic sector of the Arctic Ocean based on COADS data through 1995 [by the authors]. Cloud amount over the Atlantic sector is more even through the year.
Mean cloud cover (%) from the APP-x data set (1982-1999) for: January; April; July; and October [courtesy of J. Key, NOAA, Madison, WI].