Outline Background, climatology & variability Role of snow in the global climate system Indicators of climate change Future projections & implications of global change

Background, climatology & variability

Distinct properties of snow High albedo (α = 0.45 to 0.95) Low thermal conductivity High emissivity (ε = 0.82 to 0.99) Translucent Limited by 0 o C (low energy status) Reservoir for water Porous Mobile surface Varies greatly in space & time

Surface radiation budget over snow Q * = net radiation K↓ = incoming shortwave radiation L↓ = incoming longwave radiation L↑ = σT 4 = outgoing longwave radiation (maximum of 316 W m -2 ) Q * = K ↓ (1- α) + L ↓ + σT 4

Snow and global change science Stephen Déry, ENSC 425/ November 2006

Surface energy budget over snow Q * = net energy Q H = sensible heat flux Q E = latent heat flux (sublimation) = L s E Q G = ground heat flux Q M = snowmelt ΔQ S = change in heat storage Q * = Q H + Q E + Q G + Q M + ΔQ S

Hydrological Cycle Surface water budget:  S = P – E – R

20 th Century Climatology Observed GFDL Ref: Masuda

Current snow coverage 6 November 2006

Departure from average 6 November 2006

Seasonal climatology

Observed & GFDL Northern Hemisphere Snow Extent (x10 6 km 2 ), SeasonOBSGFDLMAERMSE Winter Spring Summer Fall Annual

Mean annual maximum monthly snow mass (kg m -2 ) in Canada, (Brown et al. 2003)

Current Snow Depth (7 Nov. 2006)

Northern Hemisphere Variability

North American Variability

Eurasian Variability

Monthly Eurasian normalized snow cover extent anomalies

Interannual variability Source: Karl et al. (1993).

Role of snow in the global climate system

Annual cycle of daily discharge in Skeena River ( ) freshet

Variation of peak discharge with latitude for 42 Hudson Bay rivers Source: Déry et al. (2005), J. Climate.

Contribution of snow to river runoff Source: Barnett et al. (2005).

Teleconnections Definition: Atmospheric interactions between widely separated regions that have been identified through statistical correlations (in space and time). For example, the El Niño teleconnection with the Southwest United States involves large-scale changes in climatic conditions that are linked to increased winter rainfall.

Correlation coefficient between annual Eurasian snow extent anomalies & discharge anomalies the following year in 64 rivers of northern Canada Source: Déry et al. (2005), JGR.

Indicators of global change Snow depth, swe, density, albedo & temperature (heat content) Duration of snow cover & growing season Snowmelt/spring freshet date Soil moisture

Snow depth Source: Curtis et al. (1998), Int. J. Climatology

Trend (%) in April lst swe, Source: Mote et al. (2005), BAMS

Albedo Source: Stone et al. (2002), JGR.

Trend (days/year) in snow cover duration,

Snowmelt Date Source: Stone et al. (2002), JGR.

Trend in centre of volume in river discharge across western N. America Source: Stewart et al. (2005), J. Climate.

Changes in annual cycle of pentad discharge for the Skeena River Source: Déry et al. (2006), in preparation.

Trends in river runoff & air temperature in Skeena River Basin

Trends in river runoff & precipitation in Skeena River Basin

Future projections & implications of global change

Components of the climate system

21 st century global climate model simulations of surface air temperature IPCC 3 rd Assessment

21st century global climate model simulations of precipitation

IPCC 4 th Assessment Runs

Trends in Northern Hemisphere snow cover extent Source: Déry et al. (2006), JGR.

Projected change in seasonal snow cover frequency based on GFDL CM2 simulations (21 st - 20 th century) Projected change in frequency -0

Trends in Northern Hemisphere snow mass

Projected change in seasonal snow water equivalent (swe) based on GFDL CM2 simulations (21 st - 20 th century) Projected change in swe (mm)

Implications of global change Increase in planetary albedo (positive feedback on global warming) Decreasing water resources, including soil moisture Longer growing season Impacts on recreational activities Ecological implications

Further reading:

Online resources: Canadian Cryospheric Information Network: National Snow and Ice Data Center: National Operational Hydrologic Remote Sensing Center: BC Ministry of Environment: Rutgers Global Snow Lab:

Thank You!!