Yo-Yo and the PIG

The rapid melting of the Pine Island Glacier (PIG) has been attributed to ocean melting. Specifically, this ocean melting is attributed to currents and tides pumping Circumpolar Deep Water (CDW) into the ice shelf cavity. To illuminate the role of tides in the melting of the PIG and the circulation and mixing at the ice shelf front, a time series of yo-yo CTD (Conductivity, Temperature, and Depth) data collected in the PIG outflow region was analyzed. The water column in the region consisted of two primary layers, a meltwater layer exiting the ice shelf cavity over a layer of CDW. Semidiurnal tides were present in both layers, with both the strength and direction of the tides differing between the two layers. The upper layer tides were stronger and directed in and out of the cavity, while the lower layer tides were primarily directed along the front of the cavity. The upper layer consisted of two meltwater layers. In the uppermost of these layers, waves with a semidiurnal frequency were propagating downward at a speed consistent with the M2 tide with the stratification. Energy was found to be transferred from the semidiurnal tide to other frequencies and to be reflected from the ice shelf front. These mechanisms were most prominent at the interfaces between layers and indicate potential mixing between the layers. In conclusion, tides were found to contribute to the circulation into the ice shelf cavity and also to mixing of the exiting water, which influences pumping of the CDW into the ice shelf cavity and melting of the PIG.