WP2: Impacts on ocean physics, biogeochemistry and phytoplankton ecology will answer the following key questions:-

Q1) What impact does internal tsunami-induced mixing have on the water column properties, specifically the stratification, mixed layer depth and heat fluxes?

Q2) How does the magnitude of this compare with other (known) generators of mixing, including near-inertial shear from winds and internal tides?

Q3) What are the biological and ecological implications of this mixing for ocean biogeochemistry (fluxes of nutrients into the photic zone) and phytoplankton ecology?

Q4) What are the implications for carbon sequestration into the deeper ocean, below the main thermocline?

To answer these questions, a combination of observational datasets collected during POLOMINTS will be used alongside regular weekly water column profiling and sampling undertaken at the RaTS site (funded separately). In addition, building on the outputs of WP1, a parameterisation of mixing from internal tsunamis will be developed and implemented in a regional oceanographic model. Baseline data from non-calving periods will be collected, including leveraging RaTS, and complementary baseline model simulations will be conducted to understand the natural spatial and temporal patterns upon which tsunami-induced mixing is superposed. The strength and mechanisms of background mixing from other sources will be assessed using historical data, reanalysis and tidal products, local meteorological data collected routinely at Rothera, and our own observational data and regional modelling, following initial procedures established in Meredith et al. (2022). The impacts of tsunami-induced vertical heat redistribution on glacier stability will be examined using simple meltwater plume theory (e.g. Jackson et al., 2020). The biogeochemical/ecological implications of mixing and impacts on nutrient and carbon fluxes will be assessed via quantification of upper-ocean nutrient stocks, and primary productivity determined through diel cycles in oxygen and modelled using bio-optical data. We will determine links between changes in water column properties (light and stratification) and nutrient stocks due to mixing impacts on phytoplankton growth rates and potential changes in community structure. Observational data will allow quantification of the effects of mixing on carbon export dynamics, inorganic and organic carbon cycling, and ocean alkalinity.