Stratigraphy and paleohydrology of lake basins in west Greenland

• Main Author: Aebly, Frank A
• Format: Text
• Language: English
• Published: DigitalCommons@University of Nebraska - Lincoln 2007
• Subjects: Geology|Hydrology|Geotechnology; Arctic; Greenland; Kangerlussuaq
• Online Access: https://digitalcommons.unl.edu/dissertations/AAI3252442

Modern observations, geomorphic and sedimentary history, and water-balance modeling were integrated to study the modern and ancient hydrologic and sedimentary processes of lakes in West Greenland. These lakes are located immediately north of the Arctic Circle and are the subject of ongoing paleoclimate investigations to characterize the natural variability of the arctic climate in this region. Observed precipitation records from Kangerlussuaq, Greenland, and atmospheric variables from the NCEP/NCAR reanalysis were used in a statistical analysis to determine controls on the seasonal variation of precipitation. Three distinct patterns of correlation between precipitation and the 500-hPa geopotential height were found to represent three dominant atmospheric patterns that strongly influence precipitation for different times of the year. Spatially dependent indices were developed based on the 500-hPa geopotential height field. The correlation coefficients between precipitation and these indices range from -0.35 to 0.55. Three parasequences identified in paleoshoreline exposures, along with seismic and ground penetrating radar data, were used to reconstruct lake-level fluctuations since deglaciation (∼8000 yr BP). Immediately following deglaciation, lake-levels dropped to ∼12-15 m below modern, but quickly rose to ∼5-6 m above modern by 5700 cal. yr BP. Lake-levels remained high until ∼3000 cal yr BP, when they declined to ∼2 m above modern. Lake-levels again increased to ∼4-5 m above modern by 2300 cal. yr BP and remained high until ∼700 cal. yr BP, after which they declined to modern values. Therefore, current lake levels are the lowest of the last ∼5700 years. Seismic data also provided evidence of subaqueous mass movements, modern sediment re-working from waves, and biogenic gas formation. Water-balance modeling resulted in mean annual precipitation anomaly (ΔMAP) estimates between +80 and +170 mm from 5700 to 3600 cal. yr BP and between +40 and +80 mm from 3000 to 700 cal. yr BP. In contrast, a ΔMAP of ∼-70 mm is ...