Late-Season High-Sedimentation Events in a Sediment Trap Record from Linnévatnet, Svalbard, Norway

• Main Author: Potter, Noel L.
• Format: Text
• Language: unknown
• Published: SCARAB 2017
• Subjects: Svalbard; Linnévatnet; lake; sediment; climate; Arctic; Norway; Spitsbergen
• Online Access: https://scarab.bates.edu/geology_theses/31; https://scarab.bates.edu/cgi/viewcontent.cgi?article=1040&context=geology_theses

Linnévatnet is a proglacial lake in the high Arctic, on the western coast of Spitsbergen, Svalbard, Norway. Svalbard’s climate is warm for its high latitude, with temperatures increasing in recent years and expected to continue rising. Given the longer and more intense melt season brought about by a warming climate, overall sedimentation may increase, and a large portion of that increase may be due to late summer and fall “shoulder season” storms falling as rain more often than as snow. This study utilizes the annual sediment trap record for the 2015-’16 accumulation year in order to document the effects of such late-season events on sedimentation in Linnévatnet, where sediment cores have yielded important high-resolution paleoclimate records. Sediment traps have been deployed in Linnévatnet since 2003, along with weather stations, time-lapse cameras, and an intervalometer, which records the timing of sediment deposition. Sediment traps are positioned to capture sediment in important zones of the lake, with special focus given to a transect from the primary inlet to the main basin. Studies of modern sedimentation patterns in the lake allow for better understanding and interpretation of sedimentary records of past climate. Meteorological and intervalometer data indicate that a rainstorm on September 11-12, 2015 yielded nearly 70% of the year’s total sediment. This contradicts the classic model of annually varved lake sediments, in which a nival flood of spring snowmelt carries most of the year’s sediment. Downcore profiles of grain size and XRF profiles of Ca, Zr, Fe, and K content distinguish sediment associated with the September rainstorm from that associated with the nival pulse. Sediment from the September rainstorm likely traveled in an irregular plume, not reaching all parts of the lake. Signatures of the nival pulse, however, were seen in all sediment traps, with some minor variations in composition representing variations in source lithology. With 70% of the year’s sediment associated with the September rainstorm, the characteristics unique to the fall storm had a significant influence on Linnévatnet’s sedimentation for the year. If shoulder season rainstorms are becoming more prevalent, it could drastically alter the sedimentation patterns in lakes like Linnévatnet.