Recent trends and variability in Canadian Arctic sea ice

Stephen Howell

Climate Research Division

January 19, 2010

Thanks to:Adrienne Tivy (IARC), Thorsten Markus (NASA); Steve McCourt (CIS); Bea Alt (CIS); Trudy Wohlleben (CIS); Claude Duguay (UW)

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Canadian Arctic Sea Ice Domain

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Canadian Arctic sea ice decreases will lag the Arctic Ocean

Holland et al., 2006-GRL(left); Sou and Flato 2009-JClim(right)

• How is Canadian Arctic sea ice responding to change?

September 10, 2041-2060 mean

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Recent trends and variability: total and multi-year sea ice

• Total sea ice area -8.7% decade-1 (sig)

• MYI area -6.4% decade-1 (not sig)

CAA September Average, 1979-2008

Howell et al. 2009-GRL;Tivy et al. submitted-JGR

Summer Average, 1968-2008

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Recent trends and variability: sea ice phenology parameters

• Melt onset -3.1 days decade -1 earlier (sig)

• Freeze onset 3.9 days decade-1 later (sig)

• Melt season length increasing at 7.0 days decade-1 (sig)

• Hudson Bay melt season length increases by 10+ days decade-1

• What is driving these changes?

Howell et al. 2009-GRL

CAA, 1979-2008

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Sea ice variability: links to surface air temperature

Tivy et al. submitted-JGR

SAT and Sea Ice, 1968-2008

NCEP SAT 1968-2008 (oC decade-1)

> 0.2oC decade-1 than pan-Arctic

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Atmospheric circulation links: Atlantic Multi-decadal Oscillation (AMO) in Hudson Bay

-20% per decade in July

Tivy et al. submitted-JClim

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Atmospheric circulation links: Arctic Oscillation & ENSO

Composite MJJAS SAT for El Niño Events

• Preceding NDJFM ENSO Index– 5 month lead

MYI Dynamic & Thermodynamic Interplay

Tivy et al. submitted-JGR

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Changes in the source input of CAA MYI

• Pre-1994; cooler temperatures (shorter melt season) less dynamic movement but situation is reversed post-1994

• When one source is shut-down the other takes over– Will result in slower decreases within the CAA

• CAA MYI for 2007 & 2008 is mostly dynamic import

Howell et al. 2009-GRL

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Late season sea ice consolidation (landfast) changes

• 2004-2007: consolidation of the ice in the CAA was ~normal

• 2008: consolidation of the ice in parts of the CAA was 6-8 weeks late

• 2009: process of normal consolidation of the ice in the CAA significantly interrupted by strong winds and warm temperatures

Courtesy T. Wohlleben (CIS)

Dec 2004 Dec 2005 Dec 2006

Dec 2007 Dec 2008 Dec 2009

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Dual-pol false-colour image: Blue = young iceRADARSAT-22 Nov 2009 HH/HV

Late season sea ice consolidation: 2009

Courtesy T. Wohlleben (CIS)

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Borden Island

Ellef Ringnes Island

Fractured Multi-year pack ice with young and first year ice in the leads

Young ice

Young ice

Young ice

Young iceMobile, fractured multi-year

ice

Fast ice

Fast ice

Fast ice

Fast ice

RADARSAT-2, HHHV, 06 Dec 2009, 1430Z

Late season sea ice consolidation: 2009

Courtesy T. Wohlleben (CIS)

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Extreme minima in 1998 and 2007

Howell et al. in prep-JGR

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Long term variability: extending the time series back to 1960

Tivy et al. submitted-JGR

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Variability in the CAA is difficult to capture

Zhang –APL; Howell and Duguay – UW; CIS

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Summary

• The Canadian Arctic is experiencing sea ice decreases but change varies regionally:

– Greatest in for Hudson Bay (~-9% per decade annually; -20 % per decade in July)– Baffin Bay (~-8.9 % per decade annually)– Beaufort Sea (~-5.2 % per decade annually)– CAA (-3% per decade annually; ~-8% per decade in September; No significant trends in

MYI)• Seasonal FYI decreases are explained mostly by summertime increases in SAT• ENSO teleconnection increases MYI in the CAA • AMO teleconnection maybe responsible for July Hudson Bay decreases• The source of CAA’s MYI has changed

– Less first-year ice survival but more dynamic MYI import attributed to an increase in the length of the melt season (~7 days per decade)

• As the transition to a summer-time sea ice free Arctic continues the supply of MYI from the Arctic Ocean to the CAA is unlikely to stop.

– Atmospheric circulation continues to force sea ice up against the CAA hence creating very thick ice (15+ m ) that will likely be able to survive 2oC temperature warming

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Anomalies continuing in 2010

• Re-fracture

Courtesy T. Wohlleben (CIS)