21st century changes in snow water equivalent over Northern Hemisphere landmasses due to increasing temperature, projected with the CMIP5 models

Abstract

Changes in snow water equivalent (SWE) over Northern Hemisphere (NH) landmasses are investigated for the early (2016–2035), middle (2046–2065) and late (2080–2099) 21st century using twenty global climate models, which are from the Coupled Model Intercomparison Project Phase 5 (CMIP5). The results show that, relative to the 1986–2005 mean, the multi-model ensemble projects a significant decrease in SWE for most regions, particularly over the Tibetan Plateau and western North America, but an increase in eastern Siberia. Seasonal SWE projections show an overall decreasing trend, with the greatest reduction in spring, which is linked to the stronger inverse partial correlation between the SWE and increasing temperature. Moreover, zonal mean annual SWE exhibits significant reductions in three Representative Concentration Pathways (RCP), a stronger linear relationship between SWE and temperature at mid–high latitudes suggests the reduction in SWE there is related to rising temperature. However, the rate of reduction in SWE declines gradually during the 21st century, indicating that the temperature may reach a threshold value that decreases the rate of SWE reduction. A large reduction in zonal maximum SWE (ZMSWE) between 30° and 40° N is evident in all 21st century for the three RCPs, while RCP8.5 alone indicates a further reduction at high latitudes in the late period of the century. This pattern implies that ZMSWE is affected not only by a terrain factor but also by the increasing temperature. In summary, our results show both a decreasing trend in SWE in the 21st century and a decline in the rate of SWE reduction over the 21st century despite rising temperatures.