HR: 0830h
AN: C41C-0997    [PDF]
TI: Barrow Ak: A Focal Point for Ice-Albedo-Transmission Feedback Processes in Arctic Sea Ice.
AU: Grenfell, T C
EM: tcg@atmos.washington.edu
AF: University of Washington, Department of Atmsopheric Sciences, MS 351640 University of Washington, Seattle, WA 98195 United States
AU: * Perovich, D K
EM: donald.k.perovich@erdc.usace.army.mil
AF: Cold Regions Research and Engineering Laboratory, ERDC-CRREL 72 Lyme Road, Hanover, NH 03755 United States
AU: Eicken, H
EM: hajo.eicken@gi.alaska.edu
AF: University of Alaska Fairbanks, Geophysical Institute University of Alaska Fairbanks 903 Koyukuk Dr. P.O. Box 757320, Fairbanks, AK 99775 United States
AB: The Arctic sea ice cover has measurably decreased in thickness, extent, and seasonal duration over the last two decades culminating in record or near-record fluctuations in 1998 and again in 2002 followed by a further strong melt season in 2003. Seasonal changes and short-term variability in the state of the ice cover and their effect on the interaction of solar radiation with the ice cover and underlying ocean are of particular importance in this context. Positive feedback processes associated with decreases in albedo and increasing transmissivity act to accelerate these changes. The rates of spring warming and summer melt as well as the length of the melt season are strongly influenced by the albedo, which in turn decreases as the melt season progresses. At the same time, increased transmission provides more energy to the upper oceanic mixed layer further increasing the potential for melting at the bottom of the ice. This ice-albedo-transmission (IAT) feedback plays a central role in modulating the heat and mass balance of the Arctic sea ice cover. Along the coastal contact zone, the feedback processes are even more complex due to interactions with the adjacent land surfaces. Indeed, this zone appears to be a focal point where the feedbacks are amplified. To understand and model the processes involved, it is necessary to determine how shortwave radiation is distributed within the ice-ocean system and how this distribution affects heat and mass balance. Analysis of this system is complicated by spatial and temporal inhomogeneity of the spring/summer ice cover, with surface conditions varying from deep snow to bare ice to melt ponds to open leads, and with ice thickness ranging from zero (open water) to ridges tens of meters thick, all within an area that is often less than one square km. Each of these categories has a different set of physical and optical properties. Treatment of the surface as a locally homogeneous medium with effective bulk optical properties represents a serious oversimplification that will significantly limit the predictive power of regional and large scale climate and dynamics models. An approach to dealing with this problem is to carry out surface-based observations of the processes involved to determine the detailed spatial and temporal variability associated with the various surface types and develop appropriate models to apply this information on larger scales. We argue that Barrow AK is critically situated for studies of the processes described above. We will present supporting results from a three-year observational sequence of heat and mass balance of the ice cover in conjunction with the interaction of solar radiation with the ice and adjacent tundra and lakes. This information allows us to make an accurate determination of partitioning of solar heating in this zone and provides the basis for IAT feedback modeling. We will also describe some modifications that will be important for generalizing to conditions attendant to increases in the length of the melt season. We propose that this type of study be continued during IPY 2007/08 and that Barrow Ak is an area of critical importance. It offers a key scientific location in combination with superior logistics support and extensive opportunities for K-12 outreach and support of higher education.
UR: http://www.arcticice.org
DE: 1635 Oceans (4203)
DE: 1863 Snow and ice (1827)
DE: 3359 Radiative processes
DE: 4207 Arctic and Antarctic oceanography
DE: 4552 Ocean optics
SC: Cryosphere [C]
MN: 2003 Fall Meeting