Varying regional δ 18 O-temperature relationship in high-resolution stable water isotopes from east Greenland
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This study examines the stable water isotope signal (δ 18 O) of three ice cores drilled on the Renland peninsula (east Greenland coast). While ice core δ 18 O measurements qualitatively are a measure of the local temperature history, the δ 18 O variability in precipitation actually reflects the integrated hydrological activity that the deposited ice experienced from the evaporation source to the condensation site. Thus, as Renland is located next to fluctuating sea ice cover, the transfer function used to infer past temperatures from the δ 18 O variability is potentially influenced by variations in the local moisture conditions. The objective of this study is therefore to evaluate the δ 18 O variability of ice cores drilled on Renland and examine the amount of the signal that can be attributed to regional temperature variations. In the analysis, three ice cores are utilized to create stacked summer, winter and annually averaged δ 18 O signals (1801-2014 CE). The imprint of temperature on δ 18 O is first examined by correlating the δ 18 O stacks with instrumental temperature records from east Greenland (1895-2014 CE) and Iceland (1830-2014 CE) and with the regional climate model HIRHAM5 (1980-2014 CE). The results show that the δ 18 O variability correlates with regional temperatures on both a seasonal and an annual scale between 1910 and 2014, while δ 18 O is uncorrelated with Iceland temperatures between 1830 and 1909. Our analysis indicates that the unstable regional δ 18 O-temperature correlation does not result from changes in weather patterns through strengthening and weakening of the North Atlantic Oscillation. Instead, the results imply that the varying δ 18 O-temperature relation is connected with the volume flux of sea ice exported through Fram Strait (and south along the coast of east Greenland). Notably, the δ 18 O variability only reflects the variations in regional temperature when the temperature anomaly is positive and the sea ice export anomaly is negative. It is hypothesized that this could be caused by a larger sea ice volume flux during cold years which suppresses the Iceland temperature signature in the Renland δ 18 O signal. However, more isotope-enabled modeling studies with emphasis on coastal ice caps are needed in order to quantify the mechanisms behind this observation. As the amount of Renland δ 18 O variability that reflects regional temperature varies with time, the results have implications for studies performing regression-based δ 18 O-temperature reconstructions based on ice cores drilled in the vicinity of a fluctuating sea ice cover.
|Journal||Climate of the Past|
|Number of pages||20|
|Publication status||Published - 16 May 2019|
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