Ready for some scientific objectives and preliminary results?
My name is Arne Bendinger, I am a third year PhD student at LEGOS (University of Toulouse III, Paul-Sabatier) studying SWOT observability of eddy-internal tide interactions around New Caledonia. One of the major objectives during my PhD is the characterization of the internal tide dynamics in this area which has never been done before, though it has been known as a generation hot spot from altimetry. Using a regional modeling approach, we have shown that the major generation sites are associated with the main bathymetric structures such as shelf breaks, ridges, and seamounts. Internal tides may play a crucial role in the waters around New Caledonia such as for marine biodiversity and productivity as they bring nutrient rich cold waters to the surface while inducing vertical mixing.
So far so good. However, observations of internal tides barely exist in this region. This is one of the objectives of SWOTALIS. In order to observe them, we have performed yo-yo CTD casts (see previous blog post from March 30, 2023).
The above figure shows such a yo-yo CTD cast of temperature over 48 h and the first results are more than convincing! The internal tides, here largely governed by the semidiurnal tide, express in isopycnal displacements with a period of roughly 12 h and feature amplitudes of up to 100 m and more at mid-depths. Such amplitude is exceptional and only known from limited places in the global ocean such as the Luzon Strait near Taiwan or the Hawaiian Ridge.
This confirms the dominance of internal tides as found in the model while raising the question to what extent SWOT will be able to observe meso- & submesoscale dynamics in an area of strong internal tide signature such as our study site south of New Caledonia which happens to be located just beneath the SWOT fast-sampling trajectory!
This is just the beginning. The whole science team is excited to see what the additional data will teach us! Stay tuned for the VMP measurements and for the objectives of our biologists aboard.
Arne Bendinger on behalf of the SWOTALIS science team aboard R/V Antea.