Novel Methods to Observe Heat and Ice in the High Latitudes Using PIES

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This project will develop and test a non-traditional method to measure the time-varying heat content and vertical temperature profile in high-latitude seas, shelves, and fjords using pressure-sensor-equipped inverted echo sounders (PIES). PIES, which are installed on the seafloor below the reach of destructive iceberg keels, present a promising and inexpensive way to improve understanding of fjord dynamics and shelf-fjord interactions and will increase long-term monitoring capabilities in high latitudes where remoteness and harsh conditions hamper traditional in situ observation techniques. The use of PIES to characterize variability at high latitudes is a novel repurposing of an existing technology, but rests on the same principle as the traditional blue-water uses for PIES: due to the dependence of sound speed on temperature, the surface-to-bottom round-trip acoustic-travel-time associated with reflections between the PIES and the air-sea interface is an excellent proxy for heat content in the intervening water column. Furthermore, since reflections from seawater-ice interfaces are also detected when ice is present, PIES also provide a means to characterize the ice component in high-latitude systems. The PIs propose to develop these methods with existing PIES data collected in a 1-year test deployment in Sermilik Fjord in eastern Greenland and with observations to be collected in a 2-year deployment of three PIES in the fjord and on the nearby shelf.