Analysis of Acoustic Scattering Layers In and Around Petermann Fjord, Northwest Greenland
In 2015 a major international collaborative expedition took place focused on understanding the processes associated with the recent rapid decline of the Greenland Ice Sheet (GIS) and the impact that this decline could have on global sea-level rise. The Petermann Expedition collected a broad range of...
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University of New Hampshire Scholars' Repository
2022
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| Online Access: | https://scholars.unh.edu/thesis/1557 https://scholars.unh.edu/cgi/viewcontent.cgi?article=2596&context=thesis |
| Summary: | In 2015 a major international collaborative expedition took place focused on understanding the processes associated with the recent rapid decline of the Greenland Ice Sheet (GIS) and the impact that this decline could have on global sea-level rise. The Petermann Expedition collected a broad range of data designed to characterize the Petermann Glacier system, a marine-terminating glacier with a floating ice tongue that has undergone dramatic changes in the last decade. During the expedition, sonars were used to map the seafloor and the water column, generating a continuous dataset over 30 days. The water column mapping revealed extensive acoustic scattering layers, so called because the components of the layer – typically zooplankton and fish – scatter acoustic energy when concentrated in layers in the water column. The scattering layer was observed to change depth in a geospatially consistent manner and corresponded to our general, but limited understanding of the complex circulation patterns in the study area. This unexpected observation became the research question investigated in this thesis: Is the distribution of the acoustic scattering layer observed in and around Petermann Fjord a proxy for spatial and temporal changes in water mass structure and interactions? In order to answer this question, we focused on four objectives: determine the geospatial distribution of the scattering layer, determine if light influences the scattering layer depth distribution, determine if there is a consistent relationship to water column structure and circulation, and investigate the components of the scattering layer for clues as to its make-up and subsequently any potential reasoning for its distribution. Understanding the distribution of water masses and their circulation patterns in Arctic fjords are critical to understanding the fate of floating ice shelves and the glaciers they buttress, as the most pronounced change is occurring where ice sheets are grounded below sea level due to enhanced interaction with warming ... |
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