Distributed Subsea Fiber-Optical Sensing along the Calving Front of a Greenlandic Tidewater Glacier

Accelerated global warming is currenting reshaping Greenland's coastal landscape becoming predominantly visible in retreating calving fronts of the ice sheet's tidewater outlet glaciers where atmospheric and oceanic environmental forcings on the cryosphere condense. Dynamic processes acting on these calving fronts not only impact future tidewater glacier evolution, but control the stability of the Greenland Ice Sheet. Rapid changes in these processes caused by global warming potentially result in the partial disintegration of the ice sheet with imminent environmental and socio-economic consequences on regional and global scales. However, quantifications of physical processes acting at tidewater glacier's calving fronts, their spatial and temporal variability and their alteration in a warming climate are inevitable for modeling glacier and ice-sheet evolution and ultimately for precise sea-level rise predictions.

Here, we present a never-before possible geophysical approach to study calving fronts, which is part of the currently ongoing multi-disciplinary GreenFjord project that aims to create process understanding of how climate change affects fjord ecosystems and how it impinges biodiversity and livelihoods. Therefore, we will install a fiber-optic cable across a Greenlandic fjord on the seafloor parallel to the calving front of a tidewater outlet glacier. We will utilize the fiber-optic cable for multi-annual Distributed Acoustic Sensing (DAS) and Distributed Temperature Sensing (DTS) simultaneously to monitor seismo-acoustic signals and temperature. With these two methods we aim to spatio-temporally resolve and quantify aerial and underwater iceberg calving, warm oceanic water intrusions at the seafloor, meltwater plume activity, underwater ice melt, fjord water stratification and mixing as well as subglacial discharge and frictional resistance at the glacier bed. In order to facilitate a system understanding, our fiber-optic measurements will be supplemented by further geophysical observations of the fjord's atmospheric, cryospheric, biospheric, and oceanic environment carried out by our project partners. Leveraged by these, our fiber-optic sensing will create a yet unresolved picture of dynamic processes at calving fronts and their role in the fjord's ecosystem.