Atmospheric River Impacts on the Greenland Ice Sheet Through the Last Interglacial

Earth's mid-latitudes host synoptic scale corridors of intense horizontal moisture transport called atmospheric rivers (ARs). These storms are responsible for substantial heat transport across the mid-latitudes and deliver large amounts of precipitation to impacted locations. ARs occasionally penetrate the Northern Hemisphere high latitudes, resulting in elevated temperatures and anomalous precipitation, which can have a major influence on the Greenland Ice Sheet (GrIS), yet the impact ARs may have had on the GrIS in past climates remains unexplored. The Last Interglacial (LIG; 130,000–115,000 years before present) featured a warmer Arctic than present and a smaller GrIS configuration, providing an ideal time period for characterizing how AR impacts on the GrIS respond to orbital forcing and GrIS topography. Here, we use existing simulations spanning the LIG with a dynamic GrIS to study AR behavior around the GrIS. Results show that there are two mechanisms for AR migration through the LIG. There is a dynamical control across the mid-latitudes through orbitally induced migrations of the prevailing winds and a thermodynamic control at high latitudes due to changes in atmospheric moisture. This results in more warm season ARs at high latitudes early in the LIG which drive substantial melt around the margins of the GrIS and accumulation on the ice sheet interior. Future AR impacts on the GrIS are shown to be similar to the early LIG where an increase in high latitude moisture increases summertime ARs and thus ice sheet ablation around the GrIS margins.