High-resolution ice cores from US ITASE (West Antarctica): development and validation of chronologies and determination of precision and accuracy

Abstract

Shallow ice cores were obtained from widely distributed sites across the West Antarctic ice sheet, as part of the United States portion of the International Trans-Antarctic Scientific Expedition (US ITASE) program. The US ITASE cores have been dated by annual-layer counting, primarily through the identification of summer peaks in non-sea-salt sulfate (nssSO 4 2-) concentration. Absolute dating accuracy of better than 2 years and relative dating accuracy better than 1 year is demonstrated by the identification of multiple volcanic marker horizons in each of the cores, Tambora, Indonesia (1815), being the most prominent. Independent validation is provided by the tracing of isochronal layers from site to site using high-frequency ice-penetrating radar observations, and by the timing of mid-winter warming events in stable-isotope ratios, which demonstrate significantly better than 1 year accuracy in the last 20 years. Dating precision to AE1 month is demonstrated by the occurrence of summer nitrate peaks and stable-isotope ratios in phase with nssSO 4 2-, and winter-time sea-salt peaks out of phase, with phase variation of <1 month. Dating precision and accuracy are uniform with depth, for at least the last 100 years.

An ice‐core proxy for northerly air mass incursions into West Antarctica

“…The US ITASE cores were melted using the University of Maine continuous melter system (Osterberg et al, 2006) and are sub-annually sampled (except for 03-1) for their entire depth (see Table I for more information). This sampling resolution captures the clear seasonal signal present in several of the glaciochemical series and allows determination of a relative dating accuracy of better than 1 year Steig et al, 2005).…”

Decadal–Interdecadal Climate Variability over Antarctica and Linkages to the Tropics: Analysis of Ice Core, Instrumental, and Tropical Proxy Data

“…In particular, a recent drilling project, the International TransAntarctic Scientific Expedition (ITASE) (Steig et al 2005), provided precisely dated records of water stable isotopes at very fine depth resolution from high accumulation rate sites over the West Antarctic ice sheet where in situ meteorological observations are few. Despite the complexities in the processes that control isotopic fractionation, most isotope modeling studies have upheld the traditional interpretation of isotope anomalies as indicators of local temperature during precipitation (Jouzel et al 1997;Werner and Heimann 2002).…”

Ice core reconstruction of Antarctic climate change and implications

“…Examples, arranged by area of scientific contribution, are listed belowIdentification of seasonal timing, source contributions, and controls on spatial distribution for all major ions (e.g. Kaspari et al 2005;Kaspari et al 2004;Dixon et al 2004;Pruett et al 2004;Han et al 2001;Isaksson et al 2001;Steig et al 2006, Bertler et al 2006a.…”