CLIMATE OSCILLATION PATTERNS DETERMINED THROUGH STABLE ISOTOPE VARIABILITY IN LACUSTRINE SEDIMENTS IN THIDRIKSVALLAVATN, ICELAND

Within the context of current global climate change, a better understanding of the oscillatory nature of climate teleconnection patterns is needed. Natural variability of such patterns can be ascertained by reconstructing climatic and environmental conditions from geologic archives such as lake sediments. In this study, we utilize the elemental and isotopic record of organic matter preserved in the sediments of Lake Thidriksvallavatn, northwestern Iceland. The lake trends E-W, and is ca. 230ha in size with a maximum depth of ca. 60m. The site is ideal for paleoclimate study because of limited anthropogenic effects as well as its location proximal to the intersection of the East Greenland Current and the Irminger Current, both affecting climate in the region. Sediment analysis was performed on lake cores collected in 1996 and 2012 (Thid FC 96-1, Thid GC 12-4). A previously published radiometric age model for an adjacent core (Thid 96-2), combined with stratigraphic analysis, provides chronologic control. Samples are at 5mm intervals, representing a sampling resolution of ~4.2 years over the past six centuries. Samples were analyzed for elemental concentration (CNS) and isotopic composition (δ¹³C, δ¹⁵N, δ³⁴S) on a continuous flow elemental analyzer/ isotope ratio mass spectrometer (EA/IRMS). Results reveal fluctuations in organic matter and productivity proxies throughout the record that are likely associated with environmental and climate variability over the Late Holocene. The most recent record is dominated by high organic carbon values, and slight increases in OC/N and δ¹³C values. Such proxies likely reveal a mixed response to increases in lake productivity, terrigenous input, and, perhaps, preservation of organic matter, associated with dam construction in the mid-twentieth century. Prior to this anthropogenic overprint, productivity proxies in the cores (OC, OC/N, δ¹³C) have distinct oscillations and their spectral analyses return significant multidecadal periodic components, similar to periods known to be associated with North Atlantic climate variability during the Holocene. Our results suggest that the productivity record from Thidriksvallavatn may preserve past variability in teleconnection patterns such as the Atlantic Multidecadal Oscillation and the North Atlantic Oscillation.