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
annual Increased Spring And Summer Cloudiness AVHRR 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 dBZ 35 GHz cloud radar ice 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 day z -30C km 100 g/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 areamass spheres aggregates, small&big
May 6. Intrieri et al., 2002 Depolarization ratio ice water Liquid/ice discrimination based on: depolarization ratio value backscattered intensity gradient Monthly-averaged percentages of Vertical columns containing liquid (grey bars) Nov Aug LIQUID FIRST
Aircraft path Lidar cloud base Temperature inversion Cloud radar reflectivity time Height (km ) 1 2 dBZ May 4 24:00 22:0023:00 UTC Liquid Characterization
How do clouds impact the surface ? J noon = 60 o 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):
Global temperature anomalies in 2005 relative to
[from G. Juday, UAF]
Record Arctic sea ice minima:
29 Aug 1980
25 Aug 2005
6 Sep 2006
Submarine- measured 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 ? J noon = 60 o 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:
Projected changes of Arctic sea ice
IPCC models: Arctic sea ice coverage,
IPCC models: Projected Arctic (60-90ºN) change of surface air temperature relative to
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:
Thank you ! Paquita Zuidema, RSMAS/MPO, MSC118
First some pure observations…