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…