Deciphering stable water isotope records of firn cores from a strongly maritime, high-accumulation site on the Antarctic Peninsula

Stable water isotope records of six firn cores retrieved from two adjacent plateaus on the northern Antarctic Peninsula between 2014 and 2016 are presented and investigated for their connections with firn-core glacio-chemical data, meteorological records and modelling results. Average annual accumulation rates of 2500 kg m-2 a-1 largely reduce the modification of isotopic signals in the snowpack by post-depositional processes, allowing excellent signal preservation in space and time. Comparison of firn-core and ECHAM6-wiso modelled delta 18O and d-excess records reveals a large agreement on annual and sub-annual scales, suggesting firn-core stable water isotopes to be representative of specific synoptic situations. The six firn cores exhibit highly similar isotopic patterns in the overlapping period (2013), which seem to be related to temporal changes in moisture sources rather than local near-surface air temperatures. Backward trajectories calculated with the HYSPLIT model suggest that prominent delta 18O minima in 2013 associated with elevated sea salt concentrations are related to long-range moisture transport dominated by westerly winds during positive SAM phases. In contrast, a broad delta 18O maximum in the same year accompanied by increased concentrations of black carbon and mineral dust corresponds to the advection of more locally derived moisture with northerly flow components (South America) when the SAM is negative.

Automated summary

Stable water isotope records from six firn cores in the northern Antarctic Peninsula were analyzed and compared with glacio-chemical data, meteorological records, and modeling results. The results showed a strong agreement between the firn-core stable water isotopes and the modeled data, suggesting that the isotopes are representative of specific synoptic situations. The records also revealed the influence of temporal changes in moisture sources on the isotopic patterns.