HR: 17:36h
AN: A24A-09    [Abstracts]
TI: Cyclone variability and its impact on moisture transport into the Arctic
AU: * Sorteberg, A
EM: asgeir.sorteberg@bjerknes.uib.no
AF: Bjerknes Centre for Climate Research, University of Bergen, Allegaten 55, Bergen, 5007, Norway
AU: Walsh, J E
EM: jwalshiarc.uaf.edu
AF: International Arctic Research Center, University of Alaska, Fairbanks, 930 Koyukuk Drive P.O. Box 757340, Fairbanks, AL 99775-7340,
AB: The Arctic is a region of moisture flux convergence, and the atmospheric water transported into the area, is a major part of the freshwater input to the Arctic Ocean, either directly through precipitation over the ocean/sea ice or as terrestrial precipitation that is then transported into the Arctic Ocean as river runoff. In addition variability or systematic changes in the moisture transport play an important role in the variability of Arctic radiation through cloud formation and water vapor. In this study characteristics of cyclones entering the Arctic (crossing 70°N) from 1949-2002 are examined. As both the cyclone number and their intensity are important for their impact on moisture transport, we have used the accumulated amount of positive relative vorticity at 70°N as a measure of cyclone activity. In terms of accumulated positive vorticity, cyclonic activity is by far most vigorous in the Greenland Sea during all seasons, except summer, when the Norwegian, Barents and Kara Sea have a comparable amount of cyclone activity. In terms of variability the Greenland Sea is also the main region. The number of cyclones traveling into the Arctic is approximately the same during all seasons, but with the winter cyclones being more intense, more variable and shorter lived than during summertime. The time series of total cyclone activity (CAI) cyclones entering the Arctic (defined as the accumulated vorticity at 70°N) indicates an upward trend (annually 3.1%/decade) that is statistical significant in three of four seasons, with the largest relative increase in summer (6.2%/decade) and spring (4.5%/decade). Further investigations should go into the causes of these strong spring and summertime trends that may have had a large impact on both sea ice dynamics and thermodynamics and the radiation characteristics of the Arctic. The cyclone activity variability at 70°N was statistically linked to the variability in moisture transport. In general the cyclone activity at 70°N is shown to be a good predictor for both seasonal and annual moisture transport variability. Annual total Arctic moisture transport variability is mainly driven by variability in cyclone activity over the Greenland, Kara and East Siberian Sea and the two regions together account for 55% of the total annual moisture transport variability. While the Greenland and East Siberian Sea cyclones are the main drivers of the Norwegian and Chukchi Sea moisture transport, respectively, the cyclones entering the Arctic from the Kara Sea is negatively correlated to the total moisture transport by reducing the Greenland Sea moisture transport as the Kara Sea cyclones will travel into the central Arctic and give northerly wind anomalies over the Greenland to Barents Sea region. Significant correlations were found between total cyclone activity and total moisture transport during winter (correlation of 0.67), autumn (0.49) and spring (0.69), while there was no connection between the two in summer (0.22). Variability and systematic changes in the Greenland and East Siberian Sea may be of particular importance, making the role of regional cyclone variability and changes an important topic in order to understand past, present and future Arctic hydrological variability.
UR: http://www.uib.no/People/gbsag/
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1620 Climate dynamics (0429, 3309)
DE: 1655 Water cycles (1836)
DE: 3305 Climate change and variability (1616, 1635, 3309, 4215, 4513)
DE: 3349 Polar meteorology
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting