Date of Graduation

Spring 5-2015

Level of Access

Restricted: Campus/Bates Community Only Access

Degree Name

Bachelor of Science

Department or Program

Geology

Number of Pages

88

First Advisor

Michael Retelle

Abstract

The warming trend of the 20th century has caused significant environmental changes to cryosphere in the arctic regions. Because the arctic plays an important role in the global climate system, it is necessary to understand how glaciers have responded to climate variation in the past in order to predict how they will react to warming in the future. Linnévatnet is a high arctic glacier-fed lake in Svalbard that serves as an excellent environmental observatory for glacial-fluvial and lake processes. Recent research on laminated lake sediments in Linnévatnet has yielded annual records of past climate that extends back at least 1,000 years. The laminae are comprised of annual couplets consisting of distinct coarse summer and fine winter layers. Analysis of sediment traps in the lake provides a calibration for interpreting the long term sediment record linking modern watershed and climatic processes to annual sediment yield.

Since 2003, arrays of sediment traps, temperature loggers and other environmental instrumentation have been deployed in a network of six moorings in Linnévatnet at depths ranging from 10 to 35 meters. The moorings are recovered annually in late summer and receiving tubes on the traps are collected and instrumentation downloaded before redeployment. In the laboratory, the receiving tubes are split, and visual stratigraphy are logged. Magnetic susceptibility was measured at 0.5 cm intervals in the split cores and the sediment was subsampled in continuous 0.25 cm slices for grain size analysis. The other halves of the cores were subsampled for mineralogical analysis using the X-Ray Diffraction method.

In the sediment traps, the spring/summer melt season and significant rain events are represented in the sediment by distinct coarse layers. In 2013-14, the first coarse (13 microns) sediment pulse seen in the traps, comprising 57% of the annual vertical accumulation, was deposited on August 15-16, 2013, coinciding with a heavy rain storm. The timing of this event was constrained by an intervalometer sediment trap and time lapse photography. Subsequent events appear as both finer (10 microns) and coarser (15 microns) laminae in the traps and are associated with rain storms later in the fall. The fine winter layer (3-5 microns) overlies the fall events and reflects quiet winter sedimentation. The beginning of the nival melt season (May 30-July 8 2014) is observed as a finer-gained (8 microns) layer, above which the coarsest (19 microns) grain sediment pulse was deposited July 9-21 2014, coinciding with peak snowmelt discharge. Sediment stratigraphy and grain size trends in 2013-2014 were compiled with sediment trap analyses back to 2004 to form a composite record to compare with lake-bottom deposition as reflected in sediment cores collected in the area.

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