| Summary: | Lake sediment cores from proglacial lakes can provide a detailed if indirect record of past glacial history and therefore past climate variations. This study involves analysis of a core from Kongressvatnet, a small lake in Kongress Valley on the high-arctic archipelago of Svalbard. Multiple characteristics of the core are examined in order to reconstruct the glacial history of the valley. There are three major questions that this study seeks to address: 1) whether during the Little Ice Age, a cold period between about the 14th and 19th centuries, the glacier that once inhabited Kongress Valley grew large enough to have contributed melt-water and sediment to Kongressvatnet, 2) what the timing and extent of the Little Ice Age in Kongressdalen was, and how this characterization compares to other locations on Svalbard and around the Northern Hemisphere, and 3) whether or not the core examined in this study records late 20th century warming. Analyses of samples from the core and of samples from fans feeding Kongressvatnet include: stratigraphic description, X-ray Diffraction, Loss on Ignition, Cesium 137 and Lead 210 dating, and bulk density. These analyses provide for three main proxies of past glacial extent: 1) X-ray Diffraction provides a carbonate index for samples, which indicates sediment provenance and therefore provides a record of activity of the glacially-fed fan, 2) LOI provides a measure of the weight percent organic matter of samples, which is used as an indicator of clastic sedimentation rate and, indirectly, glacial extent, and 3) dating provides a measure of changes in sedimentation rate, as well as chronological control for that part of the core sampled for dating. The results of this study suggest that the glacier in Kongressdalen grew large enough during the Little Ice Age to have contributed melt-water and sediment to Kongressvatnet. There is also evidence in the core of warming in the past 40-50 years from increased organic content. Instrumental measurements of the water temperature of Kongressvatnet support this finding. The results of this study provide for an overall characterization of the Little Ice Age in Kongressdalen. There are two major culminations of Little Ice Age glaciation evident in the core. The first began around or before 1320 A.D., with maximum ice extent occurring around 1330-1340 A.D. The first culmination of glaciation lasted until approximately 1400-1430 A.D. A period of conditions too warm or dry for glacial advance pervaded from approximately 1430 A.D. until about 1690-1710 A.D. The maximum ice extent during the second culmination of the LIA occurred around 1770-1800 A.D. A secondary maximum probably occurred near the end of the second culmination of the LIA; retreat from this second maximum was happening around 1929 A.D. The end of the LIA in Kongressvatnet is defined in this study as the time when retreat from the final glacial maximum was occurring, in 1929 A.D. This characterization fits fairly well with other studies conducted on Svalbard, and provides for comparison to other locations in the Northern Hemisphere.
|
|---|