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 and
atmosphere, 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
spring
Increased
Spring
And
Summer
Cloudiness
summer
1982-1999
AVHRR data
(Wang&Key, 2003)
annual
Persistent springtime cloud cover may advance snowmelt onset
date (e.g., modeling study of Zhang 1996)
Surface-based Instrumentation: May 1-8 time series
8
-45
-20
-5
dBZ
6
35 GHz cloud radar
ice cloud properties
km
4
2
depolarization lidar-determined liquid cloud base
Microwave radiometer-derived liquid water paths
100
g/m^2
1
1
2
3
4 day
6
7
day 5
4X daily soundings. Near-surface T ~ -20 C, inversion T ~-10 C
lidar cloud base
4
8
8
z
May 4 Cloud Particle Imager data
…pristine ice particles from upper cloud
...super-cooled drizzle
Most common ice particle habit: aggregate
number
area
mass
aggregates, small&big
spheres
(below liquid cloud base)
LIQUID FIRST
Liquid/ice discrimination
based on:
• depolarization ratio value
• backscattered intensity
gradient
Depolarization ratio
ice
water
Nov
May 6. Intrieri et al., 2002
Aug
Monthly-averaged percentages of
Vertical columns containing
liquid (grey bars)
Liquid Characterization
May 4
Cloud radar reflectivity
dBZ
0
2
Height (km)
-50
-50
1
Temperature inversion
Aircraft path
Lidar cloud base
22:00
UTC
23:00
time
24:00
How do clouds impact the surface ?
Jnoon = 60o
Clouds decrease surface SW by
55 W m-2 ,increase LW by 49 W m-2
Surface albedo=0.86; most SW reflected back
Clouds 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: 20022005
29 Aug 1980
25 Aug 2005
6 Sep 2006
Submarinemeasured
sea ice
thickness
Satellite data tells us sea-level heights, since 1992 a rise
of about 2 cm
Impact of
1 meter
(3 feet)
sea level
rise on FL
How do clouds impact the surface ?
Jnoon = 60o
Clouds decrease surface SW by
55 W m-2 ,increase LW by 49 W m-2
Surface albedo=0.86; most SW reflected back
Clouds 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: 20702090
Projected changes of Arctic sea ice
IPCC models: Arctic sea ice coverage, 19502100
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.org
http://nsidc.org/cryosphere/glance
http://nsidc.org/data/seaice-index/
Thank you !
Paquita Zuidema, RSMAS/MPO, MSC118
First some pure observations…