Permafrost hydrology plays an important role in global climate simulations, new study shows

Representing the soil hydrology of Arctic and subarctic regions with coarse-resolution land surface models is especially challenging because the hydrology is often determined by small-scale landscape heterogeneity and processes that are spatially and temporarily very confined. As a result, the current generation of models does not even agree on the basic question whether the high latitudes will become wetter or drier in the future.

The availability of liquid water affects almost every aspect of the land-atmosphere interactions and, using simulations with the MPI-ESM model, the researchers showed that the parametrization of the permafrost hydrology has a profound impact on the simulated cloud cover during spring and summer and thus on the planetary energy uptake. They found that the effects on the surface energy and moisture fluxes are so pronounced that uncertainties in the representation of the Arctic hydrological cycle may, indeed, help to explain a large fraction of the inter-model spread in regional surface temperatures and precipitation.

Furthermore, the parameter choices in their simulations determined the direction of the 21^st-century trend in the total soil water content. They also affected important cryospheric components of the Earth system, such as the Greenland ice sheet, Arctic sea ice cover and the thickness of subsea permafrost. Interestingly, the effects were not limited to the high northern latitudes but also reached as far to the south as the tropics with implications for droughts in the Amazon forest and vegetation in Northern Africa (Fig 1.).