Arctic Climate Change: Where Reality Exceeds ExpectationsMark C. SerrezeNational Snow and Ice Data Center (NSIDC)Cooperative Institute for Research in Environmental Sciences at the University of Colorado at Boulder

With thanks to the entire community.

Serreze et al., 2000: Observational evidence of recent change in the Northern high-latitude environment, ClimaticChange, 46, 159-207.

“Taken together, these results paint a reasonably coherent picture of change, but their interpretation as signals of enhanced greenhouse warming is open to debate.”

Seven years ago…

Why the fence-sitting?

Natural variability appearedto dominate; many changes over recent decades could be directly linked to behavior of

the NAO/NAM.

J. Hurrell (top left), M. Visbeck (top right), 0. Johannessen (bottom left)

What changed my thinking?

Figure 10.8

Increased confidence in global climate models

In many respects, reality is exceeding expectations.

Figures from the IPCC Fourth Assessment Report

Persistent trajectory despite circulation changes

Rapid loss of Arctic sea ice

September sea ice extent in 2007 compared to previous record set in 2005: A decline of 23%

Mark Serreze, Julienne Stroeve, Walt Meier, Ted Scambos, Marika Holland, Jim Maslanik, Stephanie Renfrow, Matt Savoie

2007 sea ice conditions in context

Mark Serreze, Julienne Stroeve, Walt Meier, Ted Scambos, Marika Holland, Jim Maslanik, Stephanie Renfrow, Matt Savoie

September Sea Ice Extent (1979–2007)

September 20074.28 million km2

2000

Some useful comparisons

Donald Perovich, Cold Regions Research & Engineering Laboratory

Factors contributing to the 2007 record

A very warm Arctic High pressure over central Arctic Ocean Low pressure over Siberia

NCEP/NCAR Reanalysis; NOAA/ESRL Physical Sciences Division

Sea ice is becoming younger and thinner

James Maslanik, Chuck Fowler, Julienne Stroeve

Responses to behavior in North Atlantic Oscillation/ Northern Annular Mode and other patterns Oceanic influences? A generally warming Arctic

Observed rate of loss is faster than expected

Julienne Stroeve, Mark Serreze, Walt Meier, Ted Scambos, Marika Holland

Moorings at Svinoy and Fram Strait

I. Polyakov et. al, 2005

A puzzle: warming of Atlantic inflow

K. Shimada et al., 2006

Feedback associated with Pacific summer water

Are we near a tipping point?

Ice concentration: 1990–1999 2010–2019 2040–2049

Marika Holland, Cecilia Bitz, Bruno Tremblay, Julienne Stroeve

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1900 1920 1940 1960 1980 2000 2020 2040 2060 2080 2100

Year

Ice

Ex

te

nt (

mil

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q-k

m)

CCSM3 Model SimulationObservations

Model Drop1.8 million sq km, 2024–2025

Observed Drop1.6 million sq km, 2006–2007

September Sea Ice Extent

Sea ice thickness: an intriguing comparison

Modeled ice thickness before abrupt ice loss, March 2024 (CCSM3)

Observed satellite-derived ice thickness, March 2007 (ICESat)

Marika Holland et al, 2006 (left), Julienne Stroeve (right)

Declining polar bear habitat

George Durner et al., 2007

The Northwest Passage: open by late August 2007

G. Spreen, L. Kaleschke, and G. Heygster/IUP Universitat Bremen, AMSR data from National Snow and Ice Data Center (left); unknown (upper right); Dave Kavanagh (middle right); D. Thoreson (lower right)

Manhattan1968

Gjoa1903

Cloud Nine2007

As the sea ice cover continues to retreat, the Arctic will become increasingly accessible, not just to commercial shipping, but to oil extraction.

Mike Keefe, 08/18/2007 Denver Post

An accessible Arctic

Model-Projected Arctic Amplification

Mark Serreze, Andy Barrett, Marika Holland

Model projection of 2-meter temperature anomalies by month and year for 70–90 degrees North latitude, compared to 1979–1998 means(CCSM3)

Latitude by height dependence of zonally averaged October–March temperature anomalies for 2050–2059, compared to 1979–1998 means(CCSM3)

Arctic Amplification appears to have emerged

Corresponding anomalies in 2-meter temperature (NCEP/NCAR)

Anomalies observed sea ice extentby year and month, relative to1979-2007 means, for an ArcticOcean domain (SSMR and SSM/I)

Seasonality is as expected

Andy Barrett, Mark Serreze, Matt Savoie

The vertical structure also looks correct

Latitude (0 to 90 degrees North) by height (1,000 to 100 hectopascals) dependence of temperature anomalies, 1995–2007 minus 1979–2007

October November

NCEP/NCAR, Climate Diagnostics Center

Surface melt over Greenland

2007 Melting Day Anomalies

Melting Index Time Series

Marco Tedesco, City College of New York-CUNY

Melt-induced ice flow and moulins

Konrad Steffen, CIRES at the University of Colorado at Boulder

Cryospheric sea-level rise: glaciers and ice sheets

G laciers62

G reenland28

Antarctica10

Sea Level R ise (% ) [M eier e t a l., 2007]100% = 1.8 m m a -1

G laciers70

G reenland20

Antarctica10

Sea Level R ise (% ) [IP C C , 2006]]100% = 1.28 m m a -1

G laciers50

G reenland30

Antarctica20

Sea Level R ise (% ) [la test G R A C E data)]100% = 2.2 m m a -1

Konrad Steffen, CIRES at the University of Colorado at Boulder

“Greening” of the Arctic

Trends in vegetation synthetic activity from1982–2005 (GIMMS-G AVHRR Vegetation indices)

Significant positive trends

Significant negative trends

Scott Goetz, Woods Hole

Increases in permafrost temperature

• Alaska: 4 to 6oC increase in 20th Century, 2 to 3oC, last 30 years

• Siberia: >3oC increase, mid-1950s to 1990

• Canadian Arctic: 1 to 3oC increase, past several decades

• Tibetan Plateau: up to 1.0oC increase, since1970s

Russian Permafrost Temperature

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1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

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mp

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par

ture

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0.2 m; Trend = 0.78°C/decade

0.4 m; Trend = 0.79°C/decade

0.8 m; Trend = 0.65°C/decade

1.6 m; Trend = 0.55°C/decade

3.2 m; Trend = 0.66°C/decade

Alaskan permafrost temperatures, 20 meters deep Soil temperatures, active layer/upper permafrost

Active layer depth +20 centimeters in Siberia

Tingjun Zhang, Oliver Frauenfeld, Roger Barry, Richard Armstrong, Kevin Schaefer, Larry Hinzman, David Atkinson, Andrew Etringer, James McCreight, Mark Parsons, Andrew Slater, Ted Scambos, Stephanie Renfrow, and David Gilichinsky

Decadal changes in multi-model mean freshwater budget terms for the Arctic Ocean: positive anomalies indicate an increasing source (or decreasing sink) of freshwater for the Arctic Ocean

Holland, Finnis, Barrett and Serreze, JGR, 2007

Anomalies are with respect to 1950–1980 means for ten models participating in the IPCC-AR4, A1B emissions scenario for the 21st Century

Not everything is rapidly changing…

Concluding Comments

The future is today.

Even our earliest climate models projected that effects of greenhouse gas loading would be seen first in the Arctic.

Even seven years ago, attribution of observed changes was uncertain.

Despite strong imprints of natural variability, I am now convinced of a role of greenhouse gas loading.

A number of key changes are exceeding expectations from climate models. Could we lose the summer sea ice cover by 2030?

Much remains to be understood—the idea of “tipping points” has emerged as a key issue.

Not everything is rapidly changing (hydrologic cycle).