The Imprint of Southern Ocean Stratification on the Isotopic Composition of Antarctic Precipitation

Abstract

<p class="Abstract"><span lang="EN-US">The local temperarturecannot explain the inter-annual variation in δ<sup>18</sup>O<sub>precip</sub> in the coastal Antarctic in past few decades. To understand this enigmatic variation, we have used long-term modern δ<sup>18</sup>O<sub>precip</sub> value of three coastal Antarctic sites. Using the δ<sup>18</sup>O-d-excess relationship and modelled δ<sup>18</sup>O value of vapor at source, we have shown that δ<sup>18</sup>O<sub>precip</sub> inherits the signature of moisture source parameters (MSPs). Furthermore, the wavelet analysis suggests that the variation in the MSPs impacts the seasonal cycle of δ<sup>18</sup>O<sub>precip</sub>which lead to disparity in the seasonal isotope-temperature relationship. The Southern Ocean surface stratification, due to increase in the freshwater flux by glacier melting, led to alignment of MSPs in such a manner that altogether significantly lowered the isotopic composition of initially formed vapor, which is reflected in δ<sup>18</sup>O<sub>precip</sub> at inter-annual scale.Our observations suggest that the palaeothermometry will underestimate the Antarctic temperature change for the periods characterized by warming and high glacier-melt.</span></p>