Snowfall and Water Stable Isotope Variability in East Antarctica Controlled by Warm Synoptic Events

Abstract

Understanding climate proxy records that preserve physical characteristics of past climate is a prerequisite to reconstruct long‐term climatic conditions. Water stable isotope ratios (δ18O) constitute a widely used proxy in ice cores to reconstruct temperature and climate. However, the original climate signal is altered between the formation of precipitation and the ice, especially in low‐accumulation areas such as the East Antarctic Plateau. Atmospheric conditions under which the isotopic signal is acquired at Aurora Basin North (ABN), East Antarctica, are characterized with the regional atmospheric model Modèle Atmosphérique Régional (MAR). The model shows that 50% of the snow is accumulated in less than 24 days year−1. Snowfall occurs throughout the year and intensifies during winter, with 64% of total accumulation between April and September, leading to a cold bias of −0.86°C in temperatures above inversion compared to the annual mean of −29.7°C. Large snowfall events are associated with high‐pressure systems forcing warm oceanic air masses toward the Antarctic interior, which causes a warm bias of +2.83°C. The temperature‐δ18O relationship, assessed with the global atmospheric model ECHAM5‐wiso, is primarily constrained by the winter variability, but the observed slope is valid year‐round. Three snow δ18O records covering 2004–2014 indicate that the anomalies recorded in the ice core are attributable to the occurrence of warm winter storms bringing precipitation to ABN and support the interpretation of δ18O in this region as a marker of temperature changes related to large‐scale atmospheric conditions, particularly blocking events and variations in the Southern Annular Mode.

Antarctic Atmospheric River Climatology and Precipitation Impacts

“…A more consistent categorization of moisture intrusions has potential benefits for numerical weather prediction as forecasters can look for defined blocking patterns to forecast AR landfalls and their associated impacts on extreme winds, precipitation, and explosive cyclogenesis (Waliser & Guan, 2017; Zhang et al., 2019; Zhu & Newell, 1994). In addition, moisture intrusions and precipitation variability have been shown to impact the interpretation of water stable isotopes and ice core dating (Schlosser et al., 2016; Servettaz et al., 2020; Turner et al., 2019). As ARs are related to many of these events, it is potentially possible to observe an AR impact on past climate reconstructions within ice cores.…”

Links between Large-Scale Modes of Climate Variability and Synoptic Weather Patterns in the Southern Indian Ocean

“…Synoptic types were also compared to Australian region monthly blocking indices calculated from NCEP-NCAR reanalysis data (Kalnay et al 1996) following the approach of Pook and Gibson (1999) for the Tasman Sea (1508-1808E), southern Australia (1208-1508E) and the SIO (908-1208E) sectors. Blocking in these regions influences Australian rainfall (Risbey et al 2009) and East Antarctic precipitation (Massom et al 2004;Pook et al 2006Pook et al , 2012Scarchilli et al 2011;Servettaz et al 2020).…”

Antarctic Atmospheric River Climatology and Impacts

“…The stronger zonal circumpolar ow associated with SAM+ leads to less variance in Antarctic surface temperatures due to decreased atmospheric blocking events (Marshall and Thompson [2016]). Blocking around Wilkes Land is also signi cantly negatively correlated with the SAM phase (Servettaz et al [2020]). In this region, blocking situations funnel air masses from the Indian Ocean towards Antarctica leading to moisture intrusions over the East Antarctic Plateau.…”

“…When the amplitude of the polar jet increases and blocking anticyclones form in the Southern Ocean, these synoptic cyclones can travel further inland (Hirasawa et al [2013]; Massom et al [2004]; Schlosser et al [2010]). These events are often regarded as "moisture intrusions" and have been described to cause intense temperature increases and high-precipitation events in inland regions normally cold, dry, and stable (Kurita et al [2016]; Naithani et al [2002]; Servettaz et al [2020]). When these moisture intrusions penetrate deep into the continent, they can account for a large portion of the annual precipitation budget in a short time (Bromwich [1988]; King and Turner [2007];Turner et al [2019]).…”

“…[2016]; Servettaz et al [2020]). ARs are also drive the high degree of interannual variability in precipitation across many ice core drilling sites on the continent which may complicate the dating of the ice cores (Turner et al [2019]).…”