Varying regional δ18O–temperature relationship in high-resolution stable water isotopes from east Greenland

Christian Holme, Vasileios Gkinis, Mika Lanzky, Valerie Morris, Martin Olesen, Abigail Thayer, Bruce H. Vaughn, Bo M. Vinther
2019 Climate of the Past  
<p><strong>Abstract.</strong> This study examines the stable water isotope signal (<span class="inline-formula"><i>δ</i><sup>18</sup>O</span>) of three ice cores drilled on the Renland peninsula (east Greenland coast). While ice core <span class="inline-formula"><i>δ</i><sup>18</sup>O</span> measurements qualitatively are a measure of the local temperature history, the <span class="inline-formula"><i>δ</i><sup>18</sup>O</span> variability in precipitation actually reflects the integrated
more » ... e 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 <span class="inline-formula"><i>δ</i><sup>18</sup>O</span> variability is potentially influenced by variations in the local moisture conditions. The objective of this study is therefore to evaluate the <span class="inline-formula"><i>δ</i><sup>18</sup>O</span> 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 <span class="inline-formula"><i>δ</i><sup>18</sup>O</span> signals (1801–2014&amp;thinsp;CE). The imprint of temperature on <span class="inline-formula"><i>δ</i><sup>18</sup>O</span> is first examined by correlating the <span class="inline-formula"><i>δ</i><sup>18</sup>O</span> stacks with instrumental temperature records from east Greenland (1895–2014&amp;thinsp;CE) and Iceland (1830–2014&amp;thinsp;CE) and with the regional climate model HIRHAM5 (1980–2014&amp;thinsp;CE). The results show that the <span class="inline-formula"><i>δ</i><sup>18</sup>O</span> variability correlates with regional temperatures on both a seasonal and an annual scale between 1910 and 2014, while <span class="inline-formula"><i>δ</i><sup>18</sup>O</span> is uncorrelated with Iceland temperatures between 1830 and 1909. Our analysis indicates that the unstable regional <span class="inline-formula"><i>δ</i><sup>18</sup>O</span>–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 <span class="inline-formula"><i>δ</i><sup>18</sup>O</span>–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 <span class="inline-formula"><i>δ</i><sup>18</sup>O</span> 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 <span class="inline-formula"><i>δ</i><sup>18</sup>O</span> 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 <span class="inline-formula"><i>δ</i><sup>18</sup>O</span> variability that reflects regional temperature varies with time, the results have implications for studies performing regression-based <span class="inline-formula"><i>δ</i><sup>18</sup>O</span>–temperature reconstructions based on ice cores drilled in the vicinity of a fluctuating sea ice cover.</p>
doi:10.5194/cp-15-893-2019 fatcat:xb6q6m44cfegtei22tvztvssem