discussion about two papers concerning the changing arctic sea ice geo6011seminar in geospatial...
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![Page 1: Discussion about two papers concerning the changing Arctic sea ice GEO6011Seminar in Geospatial Science and Applications Wentao Xia 11/19/2012](https://reader036.vdocuments.site/reader036/viewer/2022081516/56649ce25503460f949ad858/html5/thumbnails/1.jpg)
Discussion about two papers concerning
the changing Arctic sea ice
GEO6011Seminar in Geospatial Science and ApplicationsWentao Xia11/19/2012
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Russia
Canada
Alaska
Green
land
Arctic Ocean
Bering Strait
Chukchi Sea
Beaufort Sea
Canadian Archipelago
HudsonBay
Fury and HeclaStrait
Baffi
n Bay
Greenland
Sea
Svalbard
White Sea
Gorlo Strait
Barents Sea
Kara Sea
Laptev Sea
EasternSiberian Sea
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Discussion to Arctic sea ice
variability and trends, 1979-2010
Cavalieri D. and Parkinson C. (2012)
The Cryosphere, 6, 881-889
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SMMR-Nimbus 7
(10/26/1978-08/20/1987) SSM/I-DMSP F8,F11,F13
(07/09/1987-12/31/2007) SSM/IS-DMSP F17
(01/01/2008-present)
Data and methodWhat data does this study used?
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Technical specifications
SMMR-Nimbus 7:
Operating frequency:
6.60 GHz H/V, 10.69 GHz H/V, 18.00 GHz H/V,
21.00 GHz H/V and 37.00 GHz H/V
Spatial, temporal, and radiometric resolution: 25 km*25km, 2 days, 16-bit
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Technical specifications
SSM/I – DMSP:
Operating frequency and corresponding spatial resolution
(along track*cross track / meters):
19.35 GHz H/V 69*43,
22.235 GHz V 50*40,
37.00 GHz H/V 37*28
85.50 GHz H/V 15*13
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Technical specifications
SSM/IS – DMSP:
Operating frequency and corresponding spatial resolution
(along track*cross track / meters):
19.35 GHz H/V 73*47,
22.235 GHz V 73*47,
37.00 GHz H/V 41*31
From 50.3 to 60.72 GHz (13 bands) 17.6*27.3
91.665 GHz H/V 14*13
150 GHz 14*13
183.311 GHz (2 bands) 14*13
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Data and method
Sea ice concentration:Matching different passive microwave record
at geophysical product level Sea ice extent:Area with ≥15% ice concentration(Atmospheric interference, low ice
concentration, thin ice thickness)
How sea ice extent is defined?
Why?
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Northern hemisphere total
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Northern hemisphere total
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Northern hemisphere total
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Trend of ice extent by region
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Trend of ice extent by region
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Trend of ice extent by month and region
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Trend of ice extent by month and region
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Trend of ice extent in three periods:1979-1996, 1979-2006, 1979-2010
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Conclusion and further discussion
Northern hemisphere ice extent variability showed a declining trend.
Trend is mostly pronounced in Arctic Ocean, and in summer.
Trend of declining rapidly increased during last decade.
What trend does northern hemisphere sea ice extent variation have?
When and where the trend is strongest?
What change does such trend have in recent years?
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Discussion to The changing Arctic
sea ice cover
by Perovich D. (2011)
Oceanography 24(3):162-173
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Monthly northern hemisphere sea ice extent by passive microwave
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September ice extent abnormal
-12.8%/decadeStandard deviation=1.6%
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Ice age
First year ice survived through next September minimum is counted as multiyear ice.
Observation: Active microwave remote sensing and ice parcels tracking.
Difference: Multiyear ice tend to be thicker and more resilient to environmental forcing.
How multiyear ice defined?
How to observe ice age?
What is the most important different between first and multi year ice?
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Sea ice age derived from drift tracking of ice floes, March
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Ice thickness
Related to ice age, proxy. Field observation: with submersed upward
looking sonar onboard nuclear submarine Remote sensing: satellite altimetry Lacking continuous pan Arctic sea ice
thickness recordIs there continuous sea ice thickness data record in Arctic?
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Arctic sea ice thickness by submarine sonar
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2007 minimum event
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Explanation to 2007 extreme event
Preconditioning: loss of multiyear ice, decreasing of ice thickness
Advection of ocean heat through Bering Strait Trans-Arctic drift to Fram Strait, and warm air inflow from
Pacific by wind forcing Ice-Albedo feedback What is ice albedo feedback? Decrease in cloudiness – more impact on open water-
warmer water-more bottom and lateral melting
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Linear trend of total solar heat input directly into the ocean, percent/year
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Air and water temperature dynamics by buoy deployed at Beaufort Sea, Aug 2006 - Sep 2007
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Conclusion from two presented papers Ice extent: Declining trend- mostly due to recent extreme summer minimum
extent Ice age and thickness: Declining- due to climate change - contributing to preconditioning Extreme low summer minimum extent:- triggered by environmental forcing- triggers ice-albedo feedback- further enhancing preconditioning
What contribute most to the accelerating declining trend of Arctic sea ice extent, statistically?
What is the relationship between the declining ice age/thickness and ice extnet?
What role does ice-albedo feedback played in the process of sea ice declining?