Stable water isotopes and accumulation rates in the Union Glacier region, West Antarctica over the last 35 years

• Main Authors: Hoffmann, Kirstin, Fernandoy, Francisco, Meyer, Hanno, Thomas, Elizabeth R., Aliaga, Marcelo, Tetzner, Dieter, Freitag, Johannes, Opel, Thomas, Arigony-Neto, Jorge, Göbel, Christian Florian, Jaña, Ricardo, Rodríguez Oroz, Delia, Tuckwell, Rebecca, Ludlow, Emily, McConnell, Joseph R., Schneider, Christoph
• Format: Text
• Language: English
• Published: 2018
• Subjects: Antarctic; Antarctic Peninsula; East Antarctic Ice Sheet; Ellsworth Mountains; The Antarctic; Union Glacier; Weddell; Weddell Sea; West Antarctic Ice Sheet; West Antarctica; Antarc*; Antarctica; Ice Sheet; Sea ice
• Online Access: https://doi.org/10.5194/tc-2018-161; https://www.the-cryosphere-discuss.net/tc-2018-161/

West Antarctica is well-known as a region that is highly susceptible to atmospheric and oceanic warming. However, due to the lack of long–term and in–situ meteorological observations little is known about the magnitude of the warming and the meteorological conditions in the region at the intersection between the Antarctic Peninsula (AP), the West Antarctic Ice Sheet (WAIS) and the East Antarctic Ice Sheet (EAIS). Here we present new stable water isotope data (δ 18 O, δD, d excess) and accumulation rates from firn cores in the Union Glacier (UG) region, located in the Ellsworth Mountains at the northern edge of the WAIS. The firn core stable oxygen isotope composition reveals no statistically significant trend for the period 1980–2014 suggesting that regional changes in near-surface air temperature have been small during the last 35 years. As for stable oxygen isotopes no statistically significant trend has been found for the d excess suggesting overall little change in the main moisture sources and the origin of precipitating air masses for the UG region at least since 1980. Backward trajectory modelling revealed the Weddell Sea sector to be the likely main moisture source region for the study site throughout the year. We found that mean annual δ–values in the UG region are correlated with sea ice concentrations in the northern Weddell Sea, but are not strongly influenced by large-scale modes of climate variability such as the Southern Annular Mode (SAM) and the El Niño–Southern Oscillation (ENSO). Only mean annual d excess values are weakly positively correlated with the SAM. On average snow accumulation in the UG region amounts to about 0.25 m w.eq. a −1 between 1980 and 2014. Mean annual snow accumulation has slightly decreased since 1980 (−0.001 m w.eq. a −1 , p–value = 0.006). However, snow accumulation at UG is neither correlated with sea ice nor with SAM and ENSO confirming that the large increases in snow accumulation observed on the AP and in other coastal regions of Antarctica have not extended inland to the Ellsworth Mountains. We conclude that the UG region – located in the transition zone between the AP, the WAIS and the EAIS – is exhibiting rather East than West Antarctic climate characteristics.