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What did learn about the future Arctic from the 2008 Sea Ice Loss? James Overland and Muyin Wang NOAA/Pacific Marine Environmental Laboratory, Seattle WA , USA. Slighly Larger Sea Ice Extent in 2008 than 2007 Less Multi-Year Sea Ice in 2008 than 2007 ( Nghiem ). Lesson #1. - PowerPoint PPT Presentation
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What did learn about the future Arctic from the 2008 Sea Ice Loss?James Overland and Muyin Wang
NOAA/Pacific Marine Environmental Laboratory, Seattle WA , USA
Slighly Larger Sea Ice Extent in 2008 than 2007Less Multi-Year Sea Ice in 2008 than 2007 (Nghiem)
Lesson #1
*Summer 2008 was a second sequential summer of extreme minimum arctic sea ice extent. *Given typical summer atmospheric conditions, it will be difficult for sea ice to return to its previous state of the 1980s.
Ice Thickness Projectionfor Sept 2008
(starting 30 May) from a Sea Ice Model Forced with summer winds from different
previous yearsOnly using winds form
2007 produced additional sea ice loss
Lesson from 2008:Initial ice conditions in
general are more important than winds
J Zhang PSC/UW
Summer 2007 Weather was a Rare Event
1977 1987 20071977 1987 20071977 1987 2007
Lesson #2
*Not all of the first-year sea ice from winter 2008 melted out.*Rather than a continuation of rapid sea ice loss over the next decade, e.g. a tipping point, it may take the occurrence of several additional rare warm years such as 2007 to continue the sea ice decline.
BIG DEAL: Recent (2005-2008) Central ArcticFall Temperature Anomalies Greater Than +5 C
Loss of Sea Ice Impacts Larger Atmospheric Climate!
Fall Air Temperature Anomalies 2002-2008Reach Upper Troposphere in Atmosphere
Associated Fall Geopotential Height Anomalies 2002-2008
Reduce Jet Stream Winds in early Winter
Sfc
500 mb
500 mb
Sfc
60 N 90 N
Lesson #3
Atmospheric Climate Impact In Early Winter from Loss of Sea Ice
THE SUMMER ARCTIC ICE PACK IS MELTING AT A RATE THAT EXCEEDS MOST EXPECTATIONS
WHY SO FAST?
Anthropogenic + Unusual Meridional Climate Pattern + Ice/ocean Feedbacks = NEW STATE
Given Initial Conditions from 2007, How many years will it take to reach 1.0 M km2 in the 6 IPCC Models*? (Each Bar is an Ensemble Member)
* IPCC AR4 models that have good annual cycle of sea ice extents
Lesson #4
Given Initial Conditions of 2007-2008, better Climate Models suggest an expected value for a nearly sea-ice free Arctic in the 2030s, with large range based on Natural Variability
Lessons from 2008• Given typical summer atmospheric conditions it will be
difficult for the arctic sea ice/climate system to return to its previous state
• Rather than a continuation of rapid sea ice loss over the next decade, e.g. a tipping point, it may take the occurrence of several additional rare warm years to continue the sea ice decline.
• Large Scale Atmospheric Climate Impacts from Loss of Sea Ice Positive Feedbacks.
• Given Initial Conditions of 2007-2008, better GCMs suggest an expected value for a nearly sea-ice free Arctic in the 2030s.
September NH Sea Ice Extent from IPCC AR4 models that have good annual cycle of sea ice extents (6 out of 23)
Gray line = Control Run Red line = Observations