Sub-millennial climate variability from high-resolution water isotopes in the EPICA Dome C ice core

The EPICA Dome C (EDC) ice core provides the longest continuous climatic record, covering the last 800 000 years (800 kyr). A unique opportunity to investigate decadal to millennial variability during past glacial and interglacial periods is provided by the high-resolution water isotopic record (δ18O and δD) available for the EDC ice core. We present here a continuous compilation of the EDC water isotopic record at a sample resolution of 11 cm, which consists of 27 000 δ18O measurements and 7920 δD measurements (covering, respectively, 94 % and 27 % of the whole EDC record), including published and new measurements (2900 for both δ18O and δD) for the last 800 kyr. Here, we demonstrate that repeated water isotope measurements of the same EDC samples from different depth intervals obtained using different analytical methods are comparable within analytical uncertainty. We thus combine all available EDC water isotope measurements to generate a high-resolution (11 cm) dataset for the past 800 kyr. A frequency decomposition of the most complete δ18O record and a simple assessment of the possible influence of diffusion on the measured profile shows that the variability at the multi-decadal to multi-centennial timescale is higher during glacial than during interglacial periods and higher during early interglacial isotopic maxima than during the Holocene. This analysis shows as well that during interglacial periods characterized by a temperature optimum at the beginning, the multi-centennial variability is strongest over this temperature optimum.publishedVersio

Reconstructing Antarctic Holocene climate/environmental changes from ice and marine cores

Paleotemperature reconstructions from Antarctic ice cores rely mainly on δD and δ18O records, with the main key factors controlling their observed distribution in Antarctic surface snow being related to the condensation temperature of the precipitation and the origin of the moisture. Reconstructions of past sea-surface temperatures (SST) and sea ice cover (SIC) from marine cores at high southern latitudes mainly rely on diatom-based transfer functions. However, quantitative records of SST and SIC are concentrated in the mid-latitudes of the Southern Ocean and only few records exist in the Antarctic coastal areas. Here we present an overview of the Holocene climate records that have been compiled in the framework of the ESF-HOLOCLIP project, as well as a new isotopic record from the TALDICE ice core, recently drilled in a peripheral dome facing the Ross Sea. One of the main goals of HOLOCLIP is to reconstruct Holocene climate/environmental changes from ice and marine cores and integrate these data in model simulations. The main common features recognized in Holocene climate records obtained from ice cores are a warm early Holocene (from about 10 to 11.5 ka BP), a cool period centred at ~8 ka BP and a secondary optimum peaking at ~4 ka BP. The Holocene climate reconstructions obtained from sediment cores demonstrate a warmer early-mid Holocene hypsithermal followed by a cooler neoglacial with an amplitude and timing of the transitions variable regionally around Antarctica. Though there exist some problems in both ice and marine core records (chronologies, temporal resolution, global vs. regional, annual vs. seasonal), such approach is unique to fuel paleoclimate models and to better understand the ocean-ice-atmosphere interactions at high southern latitudes beyond the instrumental period

Infrasound detections of polar lows during the last three winters from the Norwegian infrasound station #IS18.

International audiencePolar lows are intense and very short (1 or 2 days) high latitude maritime cyclones of small horizontal (few hundred kilometers) and vertical scales (up to 5 km), that develop when very cold air is advected over relatively warmer water. Associated with severe meteorological conditions (large ocean waves, heavy precipitations, thunders and low visibility), they represent a real hazard for maritime and coastal activities but remain difficult to forecast, because of their rarity and the scarcity of observations in polar regions where they develop. With the signature of the Comprehensive Nuclear-Test-Ban Treaty (CTBT - http://www.ctbto.org) in 1996, a global infrasound monitoring network (named International Monitoring System - IMS) has been developed and provides a potential new technology to detect polar lows. According to Orbaek and Naustvik (1995), polar lows are indeed assumed to generate strong infrasound signals in the frequency range of 0.2-13 Hz, which are detectable over distances of up to 1000km. However, until recently and the exploratory study of Claud et al. (submitted), no similar study was available to generalize the possibility to use infrasound, as an alternative technology to detect and monitor polar lows. By analysing the infrasound measurements of the Norwegian infrasound station #IS18, we here try to detect the infrasound signatures of dated polar lows in the Barents and Norwegian Seas, during the 2013-2014, 2014-2015 and 2015-2016 winters