PCMDI - IPCC

A snowpack model sensitivity study, observed changes of snow cover in the NOAA satellite data set and snow cover simulations from the CMIP3 multi-model dataset are used to provide new insights into the climate response of northern hemisphere snow cover. Under conditions of warming and increasing precipitation which characterizes both observed and projected climate change over much of Northern Hemisphere land area with seasonal snow cover, the sensitivity analysis indicated snow cover duration (SCD) had the highest climate sensitivity with sensitivity varying with climate regime and elevation. The largest SCD-climate sensitivity was associated with maritime climates with extensive winter snowfall (e.g. western cordillera of North America - NA). Analysis of significant local changes in snow cover duration over the 1967-1998 period of NOAA data showed that significant decreases were concentrated in a zone where seasonal mean air temperatures were in the range of -5° to +2°C which extended around the coastal margins of the continents. These findings were echoed by the climate models which showed earlier and more widespread decreases in SCD than annual maximum snow water equivalent (SWEmax) with the zone of earliest significant decreases located over the maritime margins of NA and Western Europe. The lowest SCD-climate sensitivity was observed in continental interior climates with relative cold, dry winters and short snow cover seasons where precipitation plays a greater role in snow cover variability. The sensitivity analysis suggested a potentially complex elevation response of SCD and SWEmax to increasing T and P in mountain regions due to non-linear interactions between the duration of the snow season and snow accumulation rates.