HR: 0800h
AN: OS41A-0469    [Abstracts]
TI: Weekly to Interannual Variations of Sea-Ice Draft at the North Pole Environmental Observatory
AU: * Moritz, R E
EM: dickm@apl.washington.edu
AF: University of Washington Applied Physics Laboratory Polar Science Center, 1013 NE 40th Street, Seattle, WA 98105-6698 United States
AB: A 2-year time series of sea-ice draft D(t) was estimated from measurements made by Upward Looking Sonars (ULS) from 10 April, 2001 to 21 April, 2003. The moorings were located at the North Pole Environmental Observatory (NPEO: 89.56 N, 66.65 E in year 1; 89.45 N, 53.63 E in year 2). Sample statistics and probability density distributions (PDFs) of D(t) have been estimated by grouping the data in nonoverlapping, two-week intervals with probability weighting proportional to the ice speed recorded simultaneously by an Acoustic Doppler Current Profiler (ADCP). In the first year the sample mean draft varied from 3.7 meters in early April to 2.3 meters in late August, with an overall annual mean of 3.0 meters. The sample mean draft estimated for 15 September, 2001 is 2.3 meters, a value near the middle of the seasonally adjusted estimates derived from submarine sonar profiles near the North Pole in the 1990's (Rothrock, et al., 1999). The evolution of modal draft in year 1 lags behind the sample mean, with extrema of 2.3 meters in late June, 2001 and 1.6 meters in early January, 2002. The open water fraction (OWF), estimated by counting ice drafts smaller than .05 meters, exceeded 1 percent from mid-June to early October, and for a brief period in late December. The maximum OWF of 13 percent occurred in July, 2001. The mean ice draft was larger throughout most of the second year, especially in summer. The sample mean ice draft for 15 September, 2002 is 3.2 meters, i.e. 90 cm greater than in the preceding year, and just outside the envelope of the Rothrock values for the 1990's. Analysis of the ice draft time series, monthly mean maps of multiyear ice concentration estimated from SSM/I data, and monthly mean anomaly maps of sea level pressure suggests that ice advection played a major role in these interannual differences.
DE: 9315 Arctic region
DE: 4215 Climate and interannual variability (3309)
DE: 4540 Ice mechanics and air/sea/ice exchange processes
DE: 1635 Oceans (4203)
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting