Nares Strait Atmospheric Modeling

1
Nares Strait Atmospheric Modeling
R. M. Samelson, P. Barbour rsamelson_at_coas.oregons
tate.edu
2
Goals and Objectives

• Estimate atmospheric forcing in Nares Strait,
  where measurements are difficult to obtain
• Improve physical understanding

3
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

4
The Largest (and Coldest) Wind Tunnel on Earth?
January 2005 monthly mean 10-m wind and SLP
Nares Strait 300 km x 35 km x 500-2000 m
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
5
3-4 November 2006
From MellingH_at_pac.dfo-mpo.gc.ca 41-mb along
the Strait! This is one of the largest that I
have seenhere 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.
6
3-4 November 2006
30 m/s
500 m
22 UTC 3 Nov 2006
02 UTC 4 Nov 2006
1-6 November 2006 northward (red) and
eastward (blue) 10-m wind
7
Atmospheric Control of Sea-Ice Motion
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,
doi10.1029/2005GL025016.
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.
8
In Progress

• 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)

9
Aug 03 - Jul 05 Mean and EOFs 1 and 2
Wind speed
10
Aug 03 - Jul 05 Mean and EOFs 1 and 2
Wind stress
11
Aug 03 - Jul 05 Mean and EOFs 1 and 2
SLP
12
Aug 03 - Jul 05 EOF amplitudes
SLP 1
Wind 1
Wind Stress 1
SLP 2
13
Aug 03 - Jul 05 EOF amplitudes
SLP 2 and Wind stress 1 and 2
14
50-year Reconstructed Nares Strait Wind Time
Series
Approach Construct 50-year time-series of
Alert-Thule SLP difference convert to surface
wind and stress using linear regression derived
from model results
15
Summary

• 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