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Arctic Climate Change: Perspectives from Observations and Global Climate Models . David Lawrence NCAR With contributions from Andrew Slater, Marika Holland, Mark Serreze, Don Perovich. Observed global climate change. Spatial pattern of warming.

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arctic climate change perspectives from observations and global climate models

Arctic Climate Change: Perspectives from Observationsand Global Climate Models

David Lawrence

NCAR

With contributions from Andrew Slater, Marika Holland, Mark Serreze, Don Perovich

spatial pattern of warming
Spatial pattern of warming

Arctic warming at roughly twice the rate of the rest of the world

slide6

Greenland Ice Sheet is melting …

  • 16% increase in melt area between 1979 and 2002
  • new record in 2007 (60% increase in area)
slide7

Sea level rise

from thermal expansion of ocean water and melting glaciers

  • Since 1993
  • Global sea level
  • has risen 43 mm
  • (1.7 inches)
  • 60% from expansion as ocean temp. rise
  • 40% from melting glaciers
  • Steve Nerem
and permafrost is degrading

IPA Permafrost Distribution Map

… and permafrost is degrading

Long term monitoring site in Quebec, Canada

1957

1983

2003

Continuous (90 – 100%)

Discontinuous (50 – 90%)

Sporadic (10 – 50%)

Isolated (0 – 10%)

Permafrost

Thermokarst Ponds

Fen Vegetation

Payette et al, 2004

Brown et al. 1998

biomes are shifting tundra to shrublands
Biomes are shifting (tundra to shrublands) …

Shrub cover increasing at 1.2% per decade since 1950, 15% to 20% cover(Sturm et al. 2001, Tape et al. 2006)

and snowmen are melting
… and snowmen are melting …

Nation's Snowmen March Against Global Warming

January 25, 2006 | Issue 42-04

… Centigrade told the slowly melting snowcrowd that as recently as 15 years ago, the average life span of a snowperson built in late December was three weeks to a month. Today, that same snowperson has an average life span of two weeks.

observed arctic climate change
Observed Arctic Climate Change
  • Snow cover decreasing
  • River runoff to Arctic Ocean increasing
  • Lake and wetland distributions changing
  • Growing season is getting longer
  • More frequent forest fires
  • Rapid coastal erosion
  • ….

See, e.g. Hinzman et al., Climatic Change, 2005

McGuire et al., Ann Rev Env Res, 2006

Serreze et al., Climatic Change, 2000

Arctic Climate Impact Assessment, 2004, updated in 2008

slide12

Global Climate Model

Peering into the future ….

global climate models
Global Climate Models

Global Coupled

Ocean-Atmosphere-Land-Sea Ice model

Climate models are a lot like weather forecast models, but include interactive ocean, land, and sea-ice components, and can also account for changes in atmospheric constituents like greenhouse gases. They are used to study the earth's past, present and future climate states.

land surface model
Land-Surface Model

Rainfall

Canopy

evaporation

Transpiration

Stomatal conductance:

solar radiation, temp,

humidity deficit,

soil moisture, [CO2] …

Nitrogen fertilization

Photosynthesis model

Throughfall

Sublimation

Surface runoff

Soil evaporation

T1,

Soil hydrology

model

T2,

T3,

Runoff

Vertical water flow

Phase change

Sub-surface runoff

T10,

, T*, zo

ncar community climate system model ccsm4
NCAR Community Climate System Model (CCSM4)
  • Coupled Ocean-Atmosphere-Land- Sea Ice-Carbon cycle model
  • 1oresolution (~60 sq. miles)
  • 30 minute time step
  • 31 atmosphere levels
  • 60 ocean levels
  • 15 ground layers
  • ~5 million grid boxes
  • ~1.5 million lines of computer code
  • Archive data (monthly, daily, hourly) for over 300 geophysical fields (in land model alone)
slide18

High resolution climate model output

CAM T340- Jim Hack

David Lawrence

National Center for Atmospheric ResearchBoulder, Colorado

ccsm working groups
CCSM Working Groups

Chemistry

Climate

BioGeo

Chemistry

Atm

Model

Land

Model

Polar

Climate

Ocean

Model

Climate Change

PaleoClimate

Climate Variability

Development

Application

how do we evaluate and improve models
How do we evaluate and improve models?

Compare against observations; if comparison is poor, then something is wrong

soil and snow water storage mam son
Soil (and snow) water storage (MAM − SON)

GRACE (obs)

CCSM4

CCSM3

GRACE satellite measures small changes in gravity which on seasonal timescales are due to variations in water storage

CCSM3 and CCSM4 data from

1870 and 1850 control

300 200 100 0 -100 -200 -300 (mm)

slide23

How do we use these models to study climate change?

Economists develop possible scenarios of population growth, economic growth, energy use, land use

Depending on the scenario, more or less greenhouse gas emissions

slide24

Simulated global mean temperatures during last millenium and into 20th and 21st centuries

Ammann et al.

slide25

Air Temperature: Typical “business as usual” scenario by 2100

Global mean warming of ~2.8oC (or ~5F);Much of land area warms by ~3.5oC (or ~6.3F)Arctic warms by ~7oC (or ~12.6F)

slide26

Abrupt reductions in the September sea ice cover

September sea ice extent

Ice Extent ( 106 km2 )

SSMI observed

CCSM3

CCSM3 – smoothed

“Abrupt”

transition

Holland et al., 2006

slide28

Not far from today…

D. Perovich, CRREL

slide29

3.5-fold increase in rate of warming over land during rapid sea ice loss

September Sea- ice Extent

Lawrence et al. 2008

slide31
Goal: Represent Arctic terrestrial climate-change feedbacksin the Community Climate System Model (CCSM)

Carbon

sequester

Global

warming

CO2

efflux

CH4

efflux

Permafrost

warms and

thaws

Enhanced

[nitrogen]

Expanded

wetlands

Arctic runoff

increases

Adapted from McGuire et al., 2006

slide32

Bernhard Edmaier

National Geographic

slide33

Bernhard Edmaier

National Geographic

slide34

Bernhard Edmaier

National Geographic

slide35

Bernhard Edmaier

National Geographic