Understanding the Polar Regions in Climate Change

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Understanding theUnderstanding the Polar RegionsPolar Regions in Climate Change in Climate Change

STEM Polar Connections

AWG Glenwood Sprs, Oct 2007

Outline -- What are the Polar Regions Important toEveryone?

Bjerknes Center image, Bergen

Geography of the PolesOceans, land, sea ice and ice sheets

Definition of the ArcticTilt of the EarthCause of SeasonsChanges in Day LengthSeasonal ProductivityLinks to CO2

Earth in the BalanceOceans and THCAtmosphere T and PCryosphere

sea icesnow cover/albedoice and CO2

Continent landmasscovered with glacial icesurrounded by Ocean

Deep Oceansurrounded by Landand world’s largestcontinental shelves

Average depth of the ArcticOcean is 1038 meters (3407 ft).The deepest point is in theEurasian Basin, at 5450 meters(17,881 ft). Entire basin is 1.5 xsize of the contiguous US

Best known for its ice cover!

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Earth’s north poleis in the ArcticOcean over thedeep EurasianBasin

60% of the Arcticocean isunderlain byshallowcontinentalshelves -- thelargest in theworld!!

Greenland Icesheet

If it melted,the waterwould returnto the sea andraise globalsea level ~6.5 m (21 ft.)

Whiteness! Ice andsnow

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Contrasts in landscapes Vegetation Contrasts

Boreal forests ofbirch, spruce

Treeline ecotone

Open Tundra

What makes this a habitable planet? Whatresults from the contrast between thetropics and the poles?

How does the Earth work?What controls changes in the oceans and the atmosphere?

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68 100GulfStream

Two ways to move heat : Ocean currents

andAtmospheric Circulation

Earth’s has an axial tilt of about 23. 44 degrees, always tiltedIn the same direction throughout the year.

But as the Earth orbits the sun, tilt changeswhich hemisphere receives more Sunlightcausing the Seasons.

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•Effect of different anglesof sun•Summer solstice moreconcentrated.•Winter solstice lessconcentrated, spread out•Summer solstice hotweather on the way.Winter cooler.

• Wintersolsticeinnorthernhem

• Sunlightconc.

• Sametime,

• southernhem, sunlight isLESSconc.

• Northernhem wintersolstice,just theopposite.

• Recall Dec21, ~Xmas

• AustralianscelebrateXmas inthesummer

Ray’s slide for sun path

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Impact on Temperature

The annual cycle of global radiation (brown line) and surface air temperature(blue line) at a grid cell location in the central Beaufort Sea. Values were drawnfrom the Arctic Meteorology and Climate Atlas gridded fields for global radiationand two-meter air temperature. http://nsidc.org/arcticmet/factors/

TemperatureandBeaufort Sea

Impact on Oceans and oceancirculation

Low latitude oceans are warm and move heat to the poles

60°N

30°N

0° (Equator)

30°S

60°S

SubtropicalGyre

SubtropicalGyre

Gulf Stre

amGulf ofMexico

CaribbeanSea

North Atlantic

South Atlantic

MediterraneanSea

Eq. Countercurrent

Benguela

Curr

ent

Bra

zil C

urr

ent

Canary

Curr

ent

N. Equatorial Current

S. Equatorial Current

North Atlantic Current

West Wind Drift

East Wind Drift

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SeasonalMovement ofthe ITCZ

January(N. Hemisphere winter)

July(N. Hemisphere summer)

The great ocean conveyer: of heat and salts

Thermohaline circulation --warm waters move northward bywinds, lose heat to the atm by evaporation, become saltier,cool and sink to deep ocean

WHOI

Understanding and Projecting the Changes in the OceanicConveyor Belt is a Critical Question for Science

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Arctic inflow

The North Atlantic Currentprovides about 60% of theinflow to the Arctic Oceanbringing warmer water from theAtlantic Ocean. Some wateralso moves into the ArcticOcean from the Bering Sea andthe Pacific Ocean, by way of theBering Strait.

Arctic outflow

Water flows from the Arctic Ocean into thePacific and Atlantic Oceans, as well as into anumber of surrounding seas. By far, thegreatest volume of water leaves the ArcticOcean through the passage betweenGreenland and Spitsbergen.

http://www.aquatic.uoguelph.ca/oceans/ArticOceanWeb/Currents

The snow and ice that cover the Arctic reflect about 90% ofthe sun's energy, so the Arctic is constantly losing heat.However, the ocean currents also exchange heat;currents from the Atlantic bring warm water into the Arctic,while currents traveling southwards discharge cold water.

20031979

2010-2030 2040-2060

Sea ice extent in theArctic has hugeimage on albedo -reflectivity of EarthSurface

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Why the ArcticWarms Faster

Why the ArcticWarms Faster

A Critical Reason is that:

Timeless Arctic Marine Transport

INSROP (1999)

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• Reduced sea ice is very likely to increase marinetransport and access to resources.

In 2007, wereached whatwas predictedfor 2070 only afew years ago!

But…wow!

Laser altimetermeasurements of

Greenland Ice Sheetfrom aircraft

GPS tracking ofice movement

Recent results suggest more snowis falling on top of ice sheet, but

it is melting faster than that at theedges. Enough liquid water to fill

51 cubic kilometers in a year(lake 30 miles x 30 miles x 70

feet deep or .005 inches over theworld ocean

Cartoon x-section of ice sheet

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Letréguillyet al. 1991

Huybrechts2002

Tarasov &Peltier 2003

Cuffey & Marshall2000

ice sheet models ofsize of Greenlandduring normalwarm periods

CAPE Synthesis: CircumArctic Last Interglacial 5e Reconstruction

2.2 m min SL rise 3.4 m max SL rise

CAPE Project members,Quaternary Science Reviews, 2006

Science, 2006

Documented Sea ice extent,ice sheet melt,paleoenvironmentalreconstructions & modeling

We are tracking high end predictionsThermal expansion greater:‘93-03 data 1.6 m/myr

Not IPCC2007 40±20 cmBest estimate 80 cm global;

max. 1 m?Rahmsdorf et al. (2007)

Increase in heat W/m2

Willis et al. (2004)

Human stabilized

Natural movement 400 m

Long Beach Island, NJ

Courtesy N. Psuty

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80 cm-1m in 100 yrs80 cm-1m in 100 yrswith subsidencewith subsidencemaking it worsemaking it worse ininsome placessome places

Insurance Rates?Insurance Rates?

Disaster relief?Disaster relief?

Both needBoth needforecasting andforecasting andplanningplanning

Greenland (= 6 m of sealevel) is thinning nowBut did not disappear

during the lastInterglacial

Where AlWhere Algot it wronggot it wrong

Season Change in the Biosphere

Season changes cause zigzags in CO2 in Atm. Esp. drivenby Northern Hemisphere. In Spring - photosynthesis dropsCO2, in Fall, decomposition causes increase in CO2

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Monitoring ofCO2 and otherGreenhousegasesrecordedaround theworld

All get verysimilarmeasurements

Why?

Source: Petit et al., 1999

Now at 380 ppm

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There is no analog for thefuture we face;

we need “no regrets”strategies to reduce

vulnerability(NAS, 2002)

IPCC Projections2100 AD

CO2 (450-1100)CH4 (1500-3700)

Petit et al. (1999) Nature 399:429-436

50100150200250300350400

400

800

1200

1600

180

240

300

360

kyr BP

Today

Vostok Ice Core

380380

Summary

• For hundreds of thousands of years, the Earth hasimported heat in the tropics and exported heat viathe poles maintaining a balance.

• We are certain that as CO2 goes up and down, thetemperature of the earth follows.

• The lost of reflective surfaces in the Arctic withincreasing global temperatures leads to positivefeedbacks that warm the earth even more.

• CO2 is rising fast because of us; Mother Earth isresponding.

From NOAA

“NO REGRETS” STRATEGIES(National Research Council Report, 2002)

“…to reduce vulnerability and increaseadaptation at little or no cost , by nudgingresearch and policy in directions that willincrease the adaptability of systems”

•Energy Policies - to slow climate change

•Ecological Policies -- land use & coastal planning

•Forecasting of weather and weather related events

•Institutions -- water systems, insurance, and statisticaldata for policy reform

Geological Past andStudy of Depositional

and BiologicalSystems of

EnvironmentalChange

StrongScience

RationalDecisionMaking

GlobalEnviron-mentalPolicy