Quantification of Glacimarine Sediment Yields Using Multibeam Sonar in Alaskan Fjords

Abstract

Accurate measurement of sediment yields and inferred denudation rates is critical to assess the role of glaciation in the complex interconnection between climate and tectonics in orogenic regions. Glaciers have long been recognized as efficient modes of erosion, yet questions persist regarding potential variations in total effective erosion during different phases of tidewater glaciation. It has been argued that sediment accumulation is greatest during the retreat phase as both calving rate and ice flow velocity increase. This acceleration can potentially cause overestimation when projecting sediment yields and denudation rates beyond modern conditions. In this study we present a method to quantify temporal bathymetric changes to measure glacial sediment flux. We find that after simple processing, historical bathymetric data can be used in conjunction with multibeam bathymetry to accurately and effectively measure sea floor sediment accumulation using geospatial software. This method provides the greatest accuracy in quantifying spatial variance in sediment accumulation and therefore has advantages over point and line-derived measurements. From these data we calculate accumulation volumes, yields, and inferred denudation rates from two contrasting modern glacial systems in Southeast Alaska. Hubbard Glacier has steadily accumulated mass and advanced since at least 1895. This provides a unique opportunity to measure accumulation rates dominated by a glacier in its advance phase. Conversely, as with most Alaskan glaciers, Muir Glacier has dramatically retreated and lost mass over the last few centuries. Measured rates associated with these glaciers are compared and demonstrate sedimentation and denudation rates are analogous during both advance and retreat phases of the tidewater glacier cycle. This analysis allows for a better understanding of sedimentation patterns with tidewater glacier cycles in addition to insight on the interplay of glacial landscape denudation associated with tectonic uplift. This has ramifications not only to tectonic uplift but also to creating differential relief and over-deepening of fjord basins.

Department

Center for Coastal and Ocean Mapping

Publication Date

12-2008

Volume

89, Issue 53

Journal Title

Fall Meeting, American Geophysical Union (AGU)

Conference Date

Dec 15 - Dec 19, 2008

Publisher Place

San Francisco, CA, USA

Publisher

American Geophysical Union Publications

Document Type

Conference Proceeding

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