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