Sea Ice Exchange across the Canadian Arctic Archipelago from Microwave Satellites

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Sea Ice Exchange across the Canadian Arctic
Archipelago from Microwave Satellites

• T. A. Agnew1, J. Vandeweghe2, and A. Lambe2
• 1 Environment Canada, Toronto, Canada
• 2 Engineering Department,
• University of Toronto, Toronto, Canada

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Microwave Satellite Data

• Advanced Microwave Scanning Radiometer (AMSR)
  4-year period September 2002 to June 2006.
• RADARSAT for the earlier period (1998-2002) by
  Ron Kwok
• From these satellites you can get sea-ice area
  flux, to obtain ice volume fluxes you need
  contemporaneous ice thickness which is almost
  never available, use proxy estimates of ice
  thickness from bore hole estimates in the region,
  ULS (submarine, moored sites) and general
  knowledge of ice types in the region.
• AMSR provides daily estimates of ice motion
  every 6 pixels (37.5 km) and ice concentration at
  resolution of 12 km. However there is no data
  for July and August because ice motions are
  unreliable due to atmospheric moisture (10-month
  average Sept - June)
• RADARSAT provides 3-day ice motions on a 5 km
  grid but only for northern parts of the
  Archipelago.
• Define a number of flux gates surrounding the
  Archipelago and calculate the sea ice area flux

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Sea ice export into the North Atlantic
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Fluxgates surrounding the Archipelago
QEI-S
QEI-N
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Estimating Ice-area Flux across the Gate using
AMSR 1. Obtain an independent ice motion
estimate every 6 pixels (37.5 km ) which is
interpolate to an estimate of ice motion ui at
each 25 km intervals ?x along each fluxgate and
similarly for concentration ci. 2. Daily Ice
Area Flux ? ci ui ?x
Sea Ice Motion Error Compare with Arctic Drifting
Buoys
Separation Observations Mean Difference (km/day) SD of Difference (km/day) Mean Buoy Displacement (km/day)
1-day 198 -0.49(5) 4.64 9.74
Error in Daily Sea-ice Area Flux 1. Error in ui
is 4.64 km/day, error in ci is 10, error in ci
ui is sf 4.74 km/day 2. For example, AG gate
is L 180 km, Ns 180 km/37.5 km 5, error
daily flux across the gate is sT sf L/(Ns) ½
380 km2. 3. Monthly error s m sT (Nd) ½
2100 km2 /month
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Area Flux Error Estimate
Gate Name Gate Symbol L (km) sT (day) (km2) s (month) (km2 ) s (10-month) (km2 )
Amundsen Gulf AG 180 380 2100 6600
MClure Strait MS 180 380 2100 6600
QEI South QEI-S 180 380 2100 6600
QEI North QEI-N 135 340 1850 5840
Lancaster Sound LS 75 250 1370 4330
Jones Sound JS 45 210 1170 3690
Smith Sound SS 45 210 1170 3690
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Cumulative 10-month Area Fluxes (103 km2) each
year
Year AG MS QEI-S QEI-N LS JS SS
2003 -41 -16 33 9 45 10 8
2004 2 -15 20 4 55 13 11
2005 -8 -4 29 1 42 5 7
2006 -8 14 38 10 51 11 10
Average -14 -5 30 6 49 10 9
Estimated ice thickness (m) 1 3 3.4 3.4 1.5 - 2 1.5 1
Average volume flux (km3) -14 -15 100 20 92 15 9
Negative means export toward the Arctic
Ocean thickness from Melling (2002)
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Average Monthly Area Flux for the Northern Gates
Negative means transport toward Arctic Ocean
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AO index and Atmospheric Circulation over the
Arctic Ocean
Curtesy of Ignatias Rigor
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Pressure Gradient-Area Flux
Corr .77
Corr .74
Negative means transport toward Arctic Ocean
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RADARSAT and AMSR-E Comparison for Gates facing
the Arctic Ocean
Sensor\Gate AG (103 km2) MS (103 km2) QEI-S (103 km2) QEI-N (103 km2) NS (103 km2)
AMSR-E 2003-2006 (No July, Aug) - 14 -5 30 6
RADARSAT 1998-2002 - 85 -20 6 2 33
Estimated ice thickness (m) 1 to 1.5 3 3.4 3.4 3
Avge. Volume (km3 yr-1) -70 -42 53 12 100
Negative means export into the Arctic Ocean
Kwok (2005, 2006) Melling (2002)
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Cumulative 10-month Area Fluxes (103 km2) each
year
Year AG MS QEI-S QEI-N LS JS SS
2003 -41 -16 33 9 45 10 8
2004 2 -15 20 4 55 13 11
2005 -8 -4 29 1 42 5 7
2006 -8 14 38 10 51 11 10
Average -14 -5 30 6 49 10 9
Estimated ice thickness (m) 1 2.5 3.4 3.4 1.5 - 2 1.5 1
Average volume flux (km3) -14 -12.5 100 20 85 15 9
Positive means export into Baffin
Bay thickness from Melling (2002)
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Average Monthly Area Flux for the Southern Gates
Positive means transport toward Baffin Bay
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Net Change in Ice Area for the CAA (Net
AGMSQEI LSJS)
Month\Year 2003 (103 km2) 2004 (103 km2) 2005 (103 km2) 2006 (103 km2) Average (103 km2)
Sep 10 17 12 16 14
Oct 3 -7 -4 10 0
Nov -29 -7 -19 10 -11
Dec -23 -24 -7 -40 -24
Jan -2 -14 -9 5 -5
Feb -10 -18 -9 -13 -12
Mar -1 -7 -1 -12 -5
Apr -24 2 -5 -8 -9
May -2 -8 0 1 -2
Jun 7 10 12 21 13
10-month Average -71 -58 -30 -9 -42
Negative means net loss of sea ice
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Monthly Ice Area Budget
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Monthly Sea Ice Volume Budget
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Net Volume Advection (Net AGMSQEI LSJS)
Month\Year 2003 (103 km2) 2004 (103 km2) 2005 (103 km2) 2006 (103 km2) Average (103 km2)
Sep 33 48 36 52 43
Oct 16 -19 3 28 7
Nov -44 -18 -27 28 -15
Dec -41 -50 -11 -63 -41
Jan 11 -30 -20 25 -3
Feb -6 -28 -18 -18 -17
Mar 5 -10 2 -19 -6
Apr -36 13 -10 -13 -11
May 6 -10 8 9 4
Jun 21 35 38 52 36
10-month Average -34 -70 2 82 -5
Negative means net loss of sea ice
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Advection versus Melt/Growth
2006
2005
(importexport)
2004
2003
(growth melt)
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Conclusions

• Amundsen Gulf and MClure Strait are net
  exporters of sea ice into the Arctic Ocean (fall
  and winter) and QEI north and south gates import
  ice from the Arctic Ocean. The monthly
  variability depends on large scale circulation
  (strength and location of the Beaufort Sea
  High).
• Combining both satellite results, there is net
  export of about 50 km3 yr-1 into the Arctic Ocean
  and there is a export of 100 km3 yr-1into Baffin
  Bay. This ice is generated from within the
  Archipelago itself.
• The net ice advection each month is about 10 of
  the monthly change due to ice growth/melt.
• These fluxes are considerably less than the flux
  of sea ice through Fram Strait ( 2800 km3 yr-1).

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Fluxgates across Baffin, Davis and Fram
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Cumulative 10-month area fluxes in 103 km2 each
year
Year\Gate Baffin Bay Davis Strait Fram Strait Cornwallis Island Barrow Strait Lancaster Sound
2003 707 513 596 12 26 45
2004 641 602 699 18 33 55
2005 508 373 657 10 21 42
2006 724 494 573 19 29 51
Average 645 11 495 7 631 7 15 4 27 4 49 4
Estimated ice thickness (m) 1.5 1.5 3.5
Average volume flux (km3) 970 740 2210
Note Positive means flux southward or toward
Baffin Bay Transport for 10-months of the year
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Monthly Ice Area Flux
Positive means transport south
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Pressure Gradient-Area Flux
Negative means transport toward Arctic Ocean
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Fluxgates across Cornwallis, Barrow and Lancaster
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Monthly Ice Area Flux
Positive means transport south
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Cumulative 10-month area fluxes in 103 km2 each
year
Year\Gate Baffin Bay Davis Strait Fram Strait Cornwallis Island Barrow Strait Lancaster Sound
2003 707 513 596 12 26 45
2004 641 602 699 18 33 55
2005 508 373 657 10 21 42
2006 724 494 573 19 29 51
Average 645 11 495 7 631 7 15 4 27 4 49 4
Estimated ice thickness (m) 1.5 1.5 3.5
Average volume flux (km3) 970 740 2210
Note Positive means flux southward or toward
Baffin Bay Transport for 10-months of the year
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Modeling Sea Ice Formation/Transport in Baffin
Bay
Model daily ice transport, ice production and
salt re-distribution using sea ice cover from
AMSR rather than estimating the surface energy
budget and then melting or growing the ice
thermodynamically.
Previous days ice cover, advect it by the ice
motion, compare with the next days ice cover, ice
is grown/melted to make the advected ice field
match the next days ice cover (Pedersen and
Coon, 2004)
We obtain each day from AMSR, sea ice
concentration, sea ice type, sea ice thickness,
sea ice motion
Advect the sea ice using a trajectory method to
reduce numerical diffusion problems
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Net Freezing
2004/05
2003/04
Bathymetry


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Monthly Net Freezing/melting
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Salt Redistribution

2004/05
2003/04


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Cumulative 10-month Volume Flux in km3 each year
Year AG MS QEI-S QEI-N LS JS SS
2003 -41 -40 112 30 79 15 8
2004 2 -37 69 14 97 20 11
2005 -8 -9 99 3 74 8 7
2006 -8 34 130 33 90 17 10
Average -14 -13 102 20 85 15 9
Negative means export toward the Arctic
Ocean Melling (2002)
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Microwave Satellites

• Penetrate most cloud and do not require solar
  illumination
• RADARSAT resolution of 150 m and repeat coverage
  is 3 days (1998-2002)
• RADARSAT relies on surface scattering so you
  cannot get a contemporaneous ice thickness
  directly, must rely on proxy estimates of ice
  thickness
• Advance Microwave Scanning Radiometer for EOS
  (AMSR-E) daily repeat coverage but resolution 6
  to 12 km and no ice motion estimates in July and
  August (2003-2006)
• AMSR is multi-channel/polarization and so has
  some skill in estimating thickness of FYI
• Define a number of flux gates surrounding the
  Archipelago and calculate the sea ice area flux

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Monthly Net Ice Volume Flux and Melt/Growth
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Monthly Net Ice Area Flux and Melt/Growth
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AO Index