nares strait atmospheric modeling r. m. samelson, p. barbour [email protected]
Post on 21-Dec-2015
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TRANSCRIPT
Goals and Objectives
Estimate atmospheric forcing in Nares Strait, where measurements are difficult to obtain
Improve physical understanding
Approach
Daily mesoscale atmospheric model simulations (Polar MM5)
Forecast mode, nested in operational global model (NCEP AVN)
Archive and construct continuous hourly time series
Analyze and provide to collaborators
The Largest (and Coldest) Wind “Tunnel” on Earth?
Nares Strait: 300 km x 35 km x 500-2000 m
January 2005: monthly mean 10-m wind and SLP
Strong surface flow down pressure gradient from Lincoln Sea to Baffin Bay 9-10 months of the year
January 2005: northward (red) and eastward (blue) 10-m wind
3-4 November 2006
From: [email protected]
‘41-mb along the Strait! This is one of the largest that I have seen…here is a great thermal band image.… Note the new polynyas in north-eastern Hall and Kane Basins and the intense convection in the cold Arctic air mass as it moves out over open water in Baffin Bay. There is also indication of an ice bridge across the Lincoln Sea, with a new polynya forming there.’
3-4 November 2006
1-6 November 2006: northward (red) and eastward (blue) 10-m wind
22 UTC 3 Nov 2006 02 UTC 4 Nov 2006
30 m/s
500 m
Samelson, R. M., T. Agnew, H. Melling, and A. Münchow, 2006. Evidence for atmospheric control of sea-ice motion through Nares Strait. Geophysical Research Letters, 33, L02506, doi:10.1029/2005GL025016.
Atmospheric Control of Sea-Ice Motion
ABSTRACT: Satellite observations of ice motion are combined with model estimates of low-level winds and surface wind stress to provide evidence for atmospheric control of sea-ice motion through Nares Strait, between Ellesmere Island and Greenland, during two periods in 2004. The results suggest that ice flux through the strait, and its shutdown through the formation of a landfast ice mass in the strait, can be controlled by wind stress and atmospheric cooling. Analysis of the model results during these two periods also suggest that the intense, low-level, along-strait winds are strongly ageostrophic, and may be usefully estimated from pressure differences along the Strait.
Complete analysis of two-year (three-year?) climatology
Reconstruct 50-year wind time series from Alert-Thule SLP
Future work: Compare model winds to in-situ observations from AWS recently deployed near Davis Strait by G. W. K. Moore (U Toronto)
In Progress
Aug 03 - Jul 05: Mean and EOFs #1 and #2
Wind speed
Aug 03 - Jul 05: Mean and EOFs #1 and #2
Wind stress
Aug 03 - Jul 05: Mean and EOFs #1 and #2
SLP
Aug 03 - Jul 05: EOF amplitudes
SLP #1
Wind Stress #1SLP #2
Wind #1
Aug 03 - Jul 05: EOF amplitudes
SLP #2 and Wind stress #1 and #2
50-year Reconstructed Nares Strait Wind Time Series
Monthly MSLP Departure - THULE
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
1955 1958 1962 1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 2005
Month/Year
Pressure Departure (%)
Approach:
Construct 50-year time-series of Alert-Thule SLP difference; convert to surface wind and stress using linear regression derived from model results
Evidence found for atmospheric control of Nares Strait ice flux (GRL, 2006)
Analysis of model climatology near completion
50-year wind reconstruction in progress, using model-based SLP-wind relation
Mesoscale model simulations to continue through 2007
Summary