Understanding the Greenland Tip Jet Role in the Future: Declining Surface Heat Loss in a High-Resolution CESM Simulation (2015–99)

Abstract The Greenland tip jet is a strong mesoscale westerly wind generated by the effect of Greenland’s steep orography on the Icelandic low. This wind significantly affects air–sea heat fluxes in the Irminger Sea and can intensify deep-water formation, potentially influencing the Atlantic meridional overturning circulation (AMOC). If the frequency or strength of tip jets changes as a result of climate change, this may have important implications for the AMOC. Therefore, we analyzed the possible future of tip jets using a single high-resolution (0.25°) Community Earth System Model, version 1.3 (CESM1.3), climate simulation forced with the representative concentration pathway 8.5 (RCP8.5) scenario for 2015–99. We identified tip jet events, estimated the air–sea temperature difference, and composited anomalies of surface heat flux and wind stress associated with tip jet events. We found no significant trends in tip jet frequency or wind stress magnitude under a warming climate. However, we did find a trend in air–sea fluxes, with future ocean heat loss decreasing both during tip jet days and during boreal winter. This decrease is caused by the air–sea temperature difference decreasing as the atmosphere warms faster than the ocean water. Therefore, a decrease in air–sea temperature difference leads to a decrease in background latent and sensible heat loss. Thus, the buoyancy forcing for convection reduces even though there is no significant change in the occurrence of tip jet events. This weakened forcing will contribute to the projected decline in mixed-layer depths as a result of climate change, with likely implications for the AMOC. Significance Statement Our goal is to understand how Greenland tip jet properties may change in the future (2015–99) using a high-resolution climate simulation. The Greenland tip jet is a strong wind feature that occurs east of Cape Farewell (Greenland), persists for 1–4 days and significantly cools the central Irminger Sea. This cooling can affect the deep-water formation that can influence the Atlantic meridional overturning circulation (AMOC), a key player in the mild climate of northern Europe. Concerns arise over AMOC weakening due to shifting atmospheric conditions. Our results indicate that, although tip jets will remain as frequent in 2015–99 as observed in 1969–2015, the associated cold anomaly will decrease. This calls into question the tip jet’s future role in the AMOC.