Drift of Arctic Freshwater System in CESM Initialized Decadal Predictions

Tarun Verma, Wilbert Weijer, Jiaxu Zhang and Milena Veneziani, Los Alamos National Laboratory, Los Alamos, NM, United States
The Arctic Ocean has experienced dramatic increase in its liquid freshwater amount in the last two decades. A release of this freshwater into the subpolar North Atlantic regions could spur large scale climatic changes in the near future, through potential impact on deep convection. However, the origin of this recent buildup of freshwater, and the potential consequences of its subsequent release into the North Atlantic are unclear. The relative importance of ocean transports, cryosphere changes, or persistence of the anticyclonic regime (strengthened Beaufort high, and subsequent spin up of the underlying oceanic gyre) is not well understood. Here, we present a freshwater budget to explain oceanic, and atmospheric processes responsible for the systematic drift of the Arctic freshwater system in large ensemble of CESM initialed decadal hindcasts (CESM-DPLE). Fresh and warm initialization of the Arctic Ocean in CESM-DPLE, relative to the coupled model mean state, induces a systematic adjustment of the Arctic climate, leading to sea ice growth and loss of liquid freshwater. This reduction in Arctic liquid freshwater is a robust feature of all initialized predictions, with some variations associated with initial state; a consequence of the changing Arctic.