Coastal Trapped Waves along the Southeast Greenland Coast in a realistic numerical simulation

Ocean currents along the Southeast Greenland Coast play an important role in North Atlantic circulation and the global climate system. They carry dense water over the Denmark Strait sill, fresh water from the Arctic and the Greenland Ice Sheet into the subpolar ocean, and warm Atlantic water into Greenland’s fjords, where it can interact with outlet glaciers. Observational evidence from the OSNAP array and other mooring records shows that the circulation in this region displays substantial subinertial variability, typically with periods of several days. For the dense water flowing over the Denmark Strait sill, this variability augments the time-mean transport; on the shelf, the variability is large enough to occasionally reverse the mean transport direction of the coastal current, highlighting the importance of characterizing this variability when interpreting synoptic surveys. In this study, we used the output of a high-resolution realistic simulation to diagnose and characterize subinertial variability in sea surface height and velocity along the coast. The results show that the subinertial signals on the shelf and along the shelf break are coherent over hundreds of kilometers, and consistent with Coastal Trapped Waves in two subinertial frequency bands—at periods of 1–3 days and 5–18 days—portraying a combination of Mode I and higher modes waves. Furthermore, we find that northeasterly barrier winds may trigger the 5–18 day shelf waves, whereas the 1–3 day variability is linked to high wind speeds over Sermilik Deep.