A Paleoenvironmental Reconstruction of Linnédalen, Svalbard using Geochemical and Productivity Proxies

• Main Author: Balter, Alexandra Michelle
• Format: Text
• Language: unknown
• Published: SCARAB 2014
• Subjects: Arctic Svalbard Glacier; Arctic; Linnébreen; Linnédalen; Linnévatnet; Longyearbyen; Norway; Svalbard; albedo; Climate change; glacier; Sea ice
• Online Access: https://scarab.bates.edu/geology_theses/53; https://scarab.bates.edu/cgi/viewcontent.cgi?article=1054&context=geology_theses

The Arctic regions are particularly sensitive to changes in temperature, as warming is amplified by ice-albedo feedbacks (Serreze and Barry, 2011). Because the cryosphere plays an important role in global climate systems, it necessary to understand how sea ice and glaciers have responded to climate change in the past in order to predict how it will react to warming in the future. This study aims to reconstruct late-Holocene environmental conditions in Linnédalen, Svalbard, Norway using a 1400-year geochemical and productivity record of proglacial lake Linnévatnet. A multi-proxy approach was utilized to document physical, chemical, and biological changes preserved in the lake sediments. An 82.5 cm long core was scanned using an ITRAX XRF core scanner, which provided downcore elemental profiles at 200 μm resolution. The core was subsampled for carbon stable isotopes, organic and inorganic carbon, and chlorophyll at sub-decadal to multi-decadal resolution. An age model for the core was developed by comparing the downcore Ca:Ti ratio with that of a Linnévatnet core with a plutonium-verified varve chronology (Dowey, 2013). The first long-term paleoproductivity record in Linnévatnet was developed using chlorophyll pigment concentrations and 1400 years of sub-decadal to multi-decadal scale summer temperature was reconstructed. Characteristic geochemical signals of glacial sediment sources in the Linnévatnet catchment were determined using ITRAX data and carbon analyses. Provenance information was used in conjunction with the developed temperature reconstruction in order to make detailed inferences about the late-Holocene glacial history of Linnédalen. A period of fluctuating glaciers in Linnédalen was found from the beginning of the record to ~1300 AD. Glaciers appeared to sit at or near the Holocene glacial maximum from ~1300-1920 AD, which agrees with the timing of the LIA in Svalbard. From 1920 AD to the present, summer temperatures were unprecedented and signals of glacial retreat were observed in the geochemical record of Linnévatnet. These findings were consistent with the instrumental temperature record of Longyearbyen, Svalbard since 1911 AD, as well as documented retreat of Linnébreen since 1936 AD. A gradual decrease in the NAO index is observed throughout the LIA (Trouet et al. 2009), indicating that glacier mass balance in Linnédalen may be influenced by long-term changes in the NAO