Influence of glacial influx on the hydrodynamics of Admiralty Bay, Antarctica - a case study based on combined hydrographic measurements and numerical modeling

• Main Authors: Osińska, Maria, Herman, Agnieszka
• Format: Other/Unknown Material
• Language: unknown
• Published: Authorea, Inc. 2023
• Subjects: Admiralty Bay; Antarctic; Antarctic Bay; South Shetland Islands; Antarc*; Antarctica
• Online Access: http://dx.doi.org/10.22541/essoar.170256774.44089804/v1

This study investigates the impact of glacial water discharges on the hydrodynamics of Admiralty Bay (AB) in the South Shetland Islands, a wide bay adjacent to twenty marine-terminating glaciers. From December 2018 until February 2023, AB water properties were measured on 136 days. This dataset showed that a maximally two-layered stratification occurs in AB, and that glacial water is always the most buoyant water mass. Using the Delft3D Flow, a three-dimensional hydrodynamical model of AB was developed. During tests, the vertical position and initial velocity of glacial discharges have been shown to be insignificant for the overall bay circulation. Fourteen model scenarios have been calculated with an increasing glacial influx added. The AB general circulation pattern consists of two cyclonic cells. Even in scenarios with significant glacial input, water level shifts and circulation are predominantly controlled by the ocean. Glacial freshwater is carried out of AB along its eastern boundary in a surface layer no thicker than 60 m. Within the inner AB inlets, significant glacial influx produces buoyancy-driven vertical circulation. Using an innovative approach combining hydrographic and modeling data, a four-year, unprecedentedly high-resolution timeseries of glacial influx volumes into AB has been produced. On average, glacial influx summer values are >10 times greater than in spring and winter and 3 times higher than in autumn. The annual glacial influx into AB was estimated at 0.525 Gt. Overall, it was demonstrated how the topography and forcing controlling the hydrodynamics of an Antarctic bay differs from that of well-studied northern-hemisphere fjords.