Ecosystem greenhouse gas fluxes respond directly to weather not climate; A Case study on the relationship of global atmospheric circulation, foehn frequency, and winter weather to northern alps regional grassland phenology and carbon cycling

Desai, A. R.*; Wohlfahrt, G.*; Zeeman, M.*; Katata, Genki; Mauder, M.*; Schmid, H. P.*

The impact of climate change on regional ecosystem has two important aspects: (1) ecosystems don't respond directly to climate, but indirectly via frequency and occurrence of weather systems, (2) many responses of ecosystems to these weather patterns and extremes are lagged in time. Here, we examine these aspects for northern Alpine grasslands. Long-term flux and phenology observations in Austria and Germany and biophysical models reveal a strong influence of winter air temperature, snowfall, and snowmelt frequency on winter grass mortality and spring grassland carbon uptake. Further, the mode of climate variability that drives winter air temperature and snow depth patterns is primarily the frequency of strong regional southerly Foehn flow. Finally, we demonstrate that much of the interannual variance in Foehn frequency and southerly flow is driven by statistics and climatic trends of 500 hPa pressure patterns in Greenland, part of the Arctic Oscillation.