UNH Ocean Seminar

Using Seafloor Cables to Observe Surface Waves in High Resolution: From the Sea Ice Zone to the Surf Zone

Dr. Maddie Smith
Assistant Scientist

Applied Ocean Physics & Engineering Department
Woods Hole Oceanographic Institution

Friday, Nov. 17, 2023, 3:10pm
Chase 105

Distributed acoustic sensing (DAS) provides a novel opportunity to turn coastal seafloor telecommunication and other fiber optic cables into high-resolution surface wave measurements. A DAS interrogator is connected to the shore end of a fiber to measure strain or strain-rate by observing the reflection of lasers off impurities in the glass. Strain or strain-rate is responsive to variations in seafloor pressure (as well as acoustic and other waveforms in the water column) allowing each channel to act like a seafloor pressure mooring. This allows a fiber up to tens of kilometers in length with channel spacing of meters to act like a series of thousands of virtual wave buoys. Thus, it provides a particularly appealing method for observing spatial and temporal changes in regions with high spatial gradients, such as seasonally ice-covered coastal environments and surf zones.

In this talk, I will present results from two recent DAS experiments, where signals have been successfully used to quantify wave spectra and statistics. Results from interrogation of a telecommunication cable in the Alaskan Arctic have been used to obtain measurements of wave attenuation rates in new, partial sea ice cover. The rapid evolution of the location and strength of attenuation serves as proxy for the evolution of ice coverage and thickness, especially during rapidly evolving events. Such measurements provide notably higher spatial resolution of wave statistics than achievable by other in situ methods, as demonstrated by preliminary results from a scientific cable in the coastal Atlantic surf zone. Utilization of existing cables can require less logistical effort than in situ sampling.


Dr. Maddie Smith is an Assistant Scientist in the Applied Ocean Physics & Engineering Department at Woods Hole Oceanographic Institution. Motivated by the loss of sea ice in a rapidly changing climate, her research uses observations and modeling approaches to understand how sea ice interacts with the ocean. Her fieldwork has taken her to the oceans at both ends of the earth, including participation in the summer leg of the year-long MOSAiC expedition in the Arctic. Maddie completed her PhD in Civil & Environmental Engineering at the University of Washington.