Discussion about two papers concerning

the changing Arctic sea ice

GEO6011Seminar in Geospatial Science and ApplicationsWentao Xia11/19/2012

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

Discussion to Arctic sea ice

variability and trends, 1979-2010

Cavalieri D. and Parkinson C. (2012)

The Cryosphere, 6, 881-889

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?

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

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 ice extent:Area with ≥15% ice concentration(Atmospheric interference, low ice

concentration, thin ice thickness)

How sea ice extent is defined?

Why?

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

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?

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%/decadeStandard deviation=1.6%

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?

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 Lacking continuous pan Arctic sea ice

thickness recordIs there continuous sea ice thickness data 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 water-

warmer 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 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?