Magnitude of isotope/temperature scaling for interpretation of central Antarctic ice cores

Abstract

[1] The conventional interpretation of ice core deuterium and oxygen 18 isotope profiles based on the use of present-day observations (spatial slope) underestimates glacialinterglacial surface temperature changes in Central Greenland by up to a factor of two. This likely results from changes in the seasonality of the precipitation due to the particular location of the Greenland ice sheet next to the highly variable northern polar front. In this regard the situation is much simpler for central Antarctica and this should be reflected in the temperature interpretation of ice core isotopic records. With this in mind, we closely examine all relevant information, focusing on the East Antarctic Plateau where both model and empirical isotope-temperature estimates are available. We point to the fact that correctly accounting for the influence of ocean isotopic change is important when interpreting deuterium profiles from ice cores in this region. The evidence presently available indicates that, unlike for Greenland, the present-day spatial-slope can probably be taken as a surrogate of the temporal slope to interpret glacial-interglacial isotopic changes at sites such as Vostok and EPICA Dome C. Corresponding temperature changes are within À10% to +30% of those obtained from the conventional interpretation based on the use of the spatial slope.

A late-glacial high-resolution site and source temperature record derived from the EPICA Dome C isotope records (East Antarctica)

“…5) and as calculated by the conventional method (vT ND ) based on the use of the present-day observed temperature/isotope slope (6.04x/ ‡C) [50]. As pointed out in [27] the conventional approach and the inversion procedure, which corrects for source temperature changes, provide similar estimates of glacial^interglacial temperature changes in East Antarctica. Indeed, the source temperature correction based on the seawater-corrected deuterium excess leads to a small change of the site temperature (between 30.5 and +1.2 ‡C) between 27 and 45 kyr BP.…”

“…We account for the change in the ND and N 18 O values of surface seawater based on the N 18 O sw of Waelbroeck et al [48]. This source isotopic composition results in a smaller change at the precipitation site, proportional to 8 (1+ND) [27]. For the Dome C site, the corrected ND and N 18 O values (expressed as deviations from the present-day values) are well approximated by:…”

“…Climatic interpretation in all of these ice cores is based on either hydrogen (ND) or oxygen (N 18 O) isotopic ratios in the ice (H 2 O). The two isotopic systems enable independent ¢rst-order estimates of temperature, at least in East Antarctica [27]. Ice from the late glacial is also available from Law Dome [28] and Siple Dome [29] but continuous isotopic pro¢les spanning the late glacial period are not yet published.…”

Climatology of stable isotopes in Antarctic snow and ice: Current status and prospects

“…Though -T spatial relationship is used as a surrogate of -T temporal relationship to quantify the past temperature from ice cores [58], this method is questioned for the interpretation of glacial-interglacial stable isotopic variations over Greenland likely due to the glacial-interglacial change in the seasonality of precipitation [59]. Due to limited topographical and geographical changes between glacial and interglacial climates, Antarctica is less affected by such changes in seasonality; this gives arguments for the validity of temperature reconstruction on glacial-interglacial scale from the Antarctic interior ice cores, such as Vostok, Dome F and EPICA Dome C, with their uncertainties up to 20%-30% [60], which to great extents result from the regional changes in -T spatial slopes [21]. Additionally, changes in oceanic moisture origin conditions [27,28,60], precipitation seasonality/intermittency [35,38,39,61], Ice Sheet elevation [62,63], and atmospheric circulation may influence -T relationship, especially during the abrupt climate change.…”

“…Due to limited topographical and geographical changes between glacial and interglacial climates, Antarctica is less affected by such changes in seasonality; this gives arguments for the validity of temperature reconstruction on glacial-interglacial scale from the Antarctic interior ice cores, such as Vostok, Dome F and EPICA Dome C, with their uncertainties up to 20%-30% [60], which to great extents result from the regional changes in -T spatial slopes [21]. Additionally, changes in oceanic moisture origin conditions [27,28,60], precipitation seasonality/intermittency [35,38,39,61], Ice Sheet elevation [62,63], and atmospheric circulation may influence -T relationship, especially during the abrupt climate change. Jouzel et al [60] pointed out the necessity of making corrections for the impact of ocean stable isotopic change when interpreting the ice core stable isotopic records.…”