4:45 PM - 5:00 PM
[SCG45-12] Quantifying Abyssal Ocean Temperature Fluctuations to better Isolate Long-Term Crustal Deformation Signals.
★Invited Papers
Satellite-based geodetic measuring techniques, such as GPS and InSAR have revolutionised our understanding of crustal dynamics. Yet, due to their reliance on electromagnetic waves, GPS and InSAR can only be used to study the crust underlying ~ 30 % of the earth’s surface, since the rest is covered by ocean. The strong attenuation of electromagnetic waves in seawater has forced offshore, geodetic methods to widely rely on acoustic-ranging based methods, the resolution of which is mainly dependant on the correct representation of temporal variations in temperature, pressure, and salinity of the seawater. Such hydrographic corrections are complicated, once by the overall scarcity of hydrographic studies targeting the deep ocean, but also by their typical limitation to either spatial or temporal resolution, which has led to an oversimplification of most circulation models. Here we present the evaluation of temperature, pressure, and sound speed observations from a 2.5-year offshore geodesy experiment centred along the northern Chilean subduction zone (~21.5°S and ~71.5°W to ~70.5°W). Our analysis confirms multi-year warming trends that previous studies have reported for the deep ocean but shows an additional regionalization of warming trends. Superimposed onto the multi-year warming trend are temperature fluctuations that show multi-hourly to multi-weekly periods and amplitudes that show both spatial and depth/regional dependencies. These meso- and submesoscale heterogeneities are likely related to ocean-topography interactions through topography waves. Taken together, the observations reveal de-coupled dynamical regimes seaward and landward of the deep-sea trench that mark the extent of the abyssal part of the eastern boundary current off Chile and demonstrate the potential of time series from offshore geodetic surveys for hydrographic analyses, as well as the importance of hydrographic calibration for offshore geodesy.