Changes in the Freshwater Export from the Arctic Under Doubling of CO2

The freshwater (FW) export variability from the Arctic Ocean is a topic of great interest, as changes in the Arctic FW export have the potential to affect the deep water formation in the North Atlantic. For the 21st century, climate models predict an intensification of the hydrological cycle and a disappearance of the perennial sea-ice cover. Due to the associated freshening of the upper ocean and the phase shift from solid to liquid FW storage in the Arctic, model simulations consistently show an increase in the liquid FW export from the Arctic Ocean. In addition, the surface circulation in the Arctic Ocean might also change, due to changes in the horizontal density gradients and in the wind forcing of the ocean, with potentially large impacts on the FW pathways in the Arctic Ocean and the variability of the FW export. To investigate these changes in the Arctic Ocean, we present results from a 2 x CO2 simulation from the Community Climate System Model (CCSM), Version 3, which includes passive tracers that track FW from different sources (e.g., river runoff from different rivers, Pacific FW, precipitation, and sea ice melt). We show how the contribution of FW from different sources to the Arctic FW export changes in a seasonally ice free Arctic Ocean, how FW pathways in the Arctic Ocean are affected by the decrease of the seasonal sea ice cover, and how these changes in concentration and FW pathways affect the FW export variability from the Arctic Ocean.