The Arctic Climate

Paquita Zuidema, RSMAS/MPO, MSC 118, Feb, 29, 2008

SHEBA Surface Heat Budget of the Arctic

Early May~ 76N, 165 W

WHY ?

• GCMs indicate Arctic highly responsive to increasing greenhouse gases (e.g. IPCC)

• Clouds strongly influence the arctic surface andatmosphere, primarily through radiative interactions

• Factors controlling arctic cloudiness not well known

Observational evidence may support predictions: (Serreze et al. 2000)

Characterization and Radiative Impact of a Springtime Arctic Mixed-Phase Cloudy Boundary Layer observed during SHEBA

Paquita Zuidema

University of Colorado/NOAA Environmental Technology Laboratory, Boulder, CO

annual

IncreasedSpringAndSummerCloudiness

1982-1999AVHRR data(Wang&Key, 2003)

Persistent springtime cloud cover may advance snowmelt onset date (e.g., modeling study of Zhang 1996)

spring

summer

Surface-based Instrumentation: May 1-8 time series

35 GHz cloud radarice cloud properties

depolarization lidar-determined liquid cloud base

Microwave radiometer-derived liquid water paths

4X daily soundings. Near-surface T ~ -20 C, inversion T ~-10 C

-5-45 -20

1 2 3 4 5 6 7 8day

z

-30C

41 8

2

4

6

8

km

100g/m^2

day

-10C

lidar cloud base

May 4 Cloud Particle Imager data

…pristine ice particles from upper cloud

...super-cooled drizzle

Most common ice particle habit: aggregate

(below liquid cloud base)

number area mass

spheresaggregates, small&big

May 6. Intrieri et al., 2002

Depolarization ratioice

water

Liquid/ice discriminationbased on:• depolarization ratio value• backscattered intensity gradient

Monthly-averaged percentages ofVertical columns containing liquid (grey bars)

Nov Aug

LIQUID FIRST

Aircraft path

Lidar cloud base

Temperature inversion

Cloud radar reflectivity

time

Hei

gh

t (k

m)

1

2

dBZ0-50-50

May 4

24:0022:00 23:00UTC

Liquid Characterization

How do clouds impact the surface ?

noon = 60o

Clouds decrease surface SW by 55 W m-2 ,increase LW by 49 W m-2

Surface albedo=0.86; most SW reflected backClouds warm the surface, relative to clear skies with same T& T & RH, by time-mean 41 W m-2* (little impact at TOA)

• Can warm 1m of ice by 1.8 K/day, or melt 1 cm of 0C ice per day, barring any other mechanisms !

Local ice production more evident when boundary layer is deeper and LWPs are higher

May 3 counter-example – variable aerosol entrainment ?

Quick replenishment of liquid: longer-time-scale variability in cloud optical depth related to boundary layer depth changes

29 Aug 1980

Change in annual mean temperature (°C): 1956-2005

Global temperature anomalies in 2005 relative to 1951-1980

[from G. Juday, UAF]

Record Arctic sea ice minima: 2002-2005

29 Aug 1980

25 Aug 2005

6 Sep 2006

Submarine-measuredsea icethickness

Satellite data tells us sea-level heights, since 1992 a riseof about 2 cm

Impact of1 meter(3 feet)sea levelrise on FL

How do clouds impact the surface ?

noon = 60o

Clouds decrease surface SW by 55 W m-2 ,increase LW by 49 W m-2

Surface albedo=0.86; most SW reflected backClouds warm the surface, relative to clear skies with same T& T & RH, by time-mean 41 W m-2* (little impact at TOA)

• Can warm 1m of ice by 1.8 K/day, or melt 1 cm of 0C ice per day, barring any other mechanisms !

Cumulative volume changes of glaciers (ACIA, 2005)

North America Scandinavia Russia No. Hemis.

Extent of summer melt on Greenland

Now some future model projections…

Permafrost (CCSM)Sept. sea-ice (CCSM)Sept. sea-ice (Observed)

(Holland, Lawrence)

Projected changes of temperature: 2070-2090

Projected changes of Arctic sea ice

IPCC models: Arctic sea ice coverage, 1950-2100

IPCC models: Projected Arctic (60-90ºN) change of surface air temperature relative to 1980-2000

What are we doing about it (as scientists) ?

8 years of data from the North Slope of Alaska DOE/ARM site

Great websites with real-time data, historical fotos:

http://www.arctic.noaa.gov/

http://nsidc.orghttp://nsidc.org/cryosphere/glancehttp://nsidc.org/data/seaice-index/

Thank you !

Paquita Zuidema, RSMAS/MPO, MSC118

First some pure observations…