Quantifying Northern Hemisphere freshwater ice


Corresponding author: R. N. Brooks, Water and Climate Impacts Research Centre, University of Victoria, Victoria, BC V8W 3R4, Canada. (rbrooks@uvic.ca)


[1] The areal extent and volume of peak freshwater (river and lake) ice are quantified across the Northern Hemisphere for the period 1957–2002. Quantification is conducted using a degree-day ice growth model and ice growth coefficients defined for 14 ice-specific hydroclimatic regions. The model is driven by ERA-40 gridded daily air temperature data, and the Global Lakes and Wetlands Database is employed to spatially define rivers and lakes. Results indicate that the total area covered by freshwater ice, at peak thickness, north of the January 0°C isotherm (excluding the Greenland ice sheet) is 1.7 × 106 km2 and the total freshwater ice volume is 1.6 × 103 km3. This area is approximately equal to that of the Greenland ice sheet and the volume to snow on land (Northern Hemisphere). Such values now permit a more complete quantification of the cryosphere (evaluations already having been completed for other components, such as snow, glaciers, and sea ice) and provide a reference data set for assessing future climate-related changes.