Dating of the Berkner, Fletcher and James Ross ice cores and implications

Titre : Dating of the Berkner, Fletcher and James Ross ice cores and implications

Laboratoire de rattachement : LGGE

Encadrant : Frédéric Parrenin,

Téléphone :0476824265

Co-Encadrant : Jérôme Chappellaz,

Mots clés : Paleoclimatology, Antarctica, ice cores, chronology, ice flow

Contexte et objectifs de la mission de stage :

Ice cores provide a good deal of crucial information on past climates, like the temperature above ice sheets (Jouzel et al., 2007), the atmospheric concentration of greenhouse gases (Loulergue et al., 2008 ; Lüthi et al., 2008) or the flux of various aerosols (Wolff et al., 2006), from continental, marine or volcanic origin. Recently, ice cores have been drilled in coastal regions of Antarctica to constrain the past local climate of these areas. The James Ross ice (JRI) core has been drilled on an island at the tip of the Antarctic peninsula while the Fletcher and Berkner ice cores have been retrieved on ice rises situated in the Ronne-Filchner ice shelf. The dating of ice cores is a prerequisite before any interpretation of the ice core records. Moreover, the age scale construction can give clues on the past flow of ice by, e.g., estimating the vertical thinning of ice layers.
The aim of this internship will be to date these 3 ice cores and to analyze the paleoclimatic and glaciological implications of these datings. A section of the JRI ice core will be analyzed using a continuous flow analysis (CFA) method, measuring in particular the CH4 concentration of air bubbles and some discrete measurements will be performed on the Berkner and Fletcher ice cores. Together with previous measurements, this will allow synchronizing these ice cores to well-dated records, like the ones from central Antarctica (e.g., EDC). These ice cores records will consequently be placed on the official AICC2012 chronology (Bazin et al., 2013 ; Veres et al., 2013) and the vertical thinning of ice layers will be deduced using the probabilistic dating model IceChrono1, developed at LGGE (Parrenin et al., 2015). Possible scenarios of ice flow will then be discussed, also taking into account the temperature profiles measured in the ice cores.