Discussion about
two papers concerning
the changing Arctic sea ice
GEO6011Seminar in Geospatial Science and
Applications
Wentao Xia
11/19/2012
Bering Strait
Alaska
Chukchi Sea
Canada
Laptev Sea
Russia
Canadian
Archipelago
Arctic Ocean
Hudson
Bay
Fury and Hecla
Strait
Kara Sea
Svalbard
Barents Sea
Gorlo Strait
White Sea
Discussion to
Arctic sea ice
variability and trends, 1979-2010
Cavalieri D. and Parkinson C. (2012)
The Cryosphere, 6, 881-889
Data and method
What data does this study used?
 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)
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, 16bit

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

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

Data and method
Sea ice concentration:
Matching different passive microwave record
at geophysical product level
 Sea
iceice
extent:
How
sea
extent is defined?
Area with ≥15% ice concentration
Why?
(Atmospheric interference, low ice
concentration, thin ice thickness)

Northern hemisphere total
Northern hemisphere total
Northern hemisphere total
Trend of ice extent by region
Trend of ice extent by region
Trend of ice extent by month and region
Trend of ice extent by month and region
Trend of ice extent in three periods:
1979-1996, 1979-2006, 1979-2010
Conclusion and further discussion
trend
does northern
hemisphere
What
Northern
hemisphere
ice extent
variability
sea
ice
extenta variation
have?
showed
declining trend.
When and where the trend is strongest?

Trend is mostly pronounced in Arctic Ocean, and
in summer.
doesrapidly
suchincreased
trend have
in
What
Trendchange
of declining
during
decade.
recent
years?
last
Discussion to
The changing Arctic
sea ice cover
by Perovich D. (2011)
Oceanography 24(3):162-173
Monthly northern hemisphere sea ice extent by
passive microwave
September ice extent abnormal
-12.8%/decade
Standard deviation=1.6%
Ice age
How
Firstmultiyear
year ice
survived
through next
ice
defined?
September minimum is counted as
multiyear ice.
How
Observation:
microwave remote
to observeActive
ice age?
sensing and ice parcels tracking.
What
Difference:
Multiyear
ice tend
to bebetween
thicker
is the most
important
different
andand
more
resilient
to environmental forcing.
first
multi
year ice?
Sea ice age derived from drift tracking of ice floes, March
Ice thickness
Related to ice age, proxy.
 Field observation: with submersed upward
looking sonar onboard nuclear submarine
 Remote sensing: satellite altimetry
IsLacking
continuous
pan
sea ice
there continuous
sea
iceArctic
thickness
data
thickness
record
record
in Arctic?

Arctic sea ice thickness by submarine sonar
2007 minimum event
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 waterwarmer water-more bottom and lateral melting
Linear trend
of total solar heat input directly into the ocean,
percent/year
Air and water temperature dynamics by buoy
deployed at Beaufort Sea, Aug 2006 - Sep 2007
Conclusion from two presented papers
What contribute most to the accelerating declining
 Ice extent: Declining trend
trend of Arctic sea ice extent, statistically?
- mostly due to recent extreme summer minimum
extent
is the
relationship
What
Ice age
and
thickness:between
Decliningthe declining ice
ice extnet?
-age/thickness
due to climateand
change
- contributing to preconditioning
What
Extreme
low summer
minimum
extent:
role does
ice-albedo
feedback
played in the
-process
triggered
by environmental
of sea
ice declining? forcing
- triggers ice-albedo feedback
- further enhancing preconditioning