Atmospheric regime of dust and salt through 75,000 years of Taylor Dome ice core: Refinement by measurement of major, minor, and trace metal suites

Abstract

Abstract. Measurement of absolute and relative amounts of dust and salt deposited in the polar ice record is central to several fields of study, including nutrient delivery, atmospheric deposition of trace elements, past wind strengths, dust provenance, and other aspects of climate and geochemical history. We present a method intended to give a more accurate picture than has been possible before of the total amounts and relative proportions of the dust and salt deposited by the atmosphere into polar ice. It also permits us to distinguish different compositional types of dust in the ice. The method is based on precise measurement of a suite of several metals whose proportions contrast strongly between dust and salt and vary substantially between dust types. We apply the method to a small suite of ice samples from the Taylor Dome core in coastal West Antarctica. In full glacial times, when total impurities were high and dust dominated over salt, wind strength in the West Antarctic region was apparently high, and extensive sea-ice cover prevented incorporation of salt into the atmospheric load. At the termination of the glacial period, increased salt in the dust-salt mixture indicates that sea ice diminished, but wind strength continued high, and unchanged dust composition indicates unchanged source areas. At about 10,000-11,000 y.B.P., sea-ice cover appears to have briefly returned to glacial conditions, but wind conditions remained in the milder postglacial condition. Soon after, sea ice retreated, and an abrupt change in dust composition indicates changed source materials or terranes. If extended by analysis of more samples from more sites, such information on salt and dust could provide firm constraints on past wind strengths, extent of sea-ice cover, deposition fluxes of salt and dust, and changing continental source areas of dust, for both polar regions of the Earth. The method we present here for measuring the absolute and relative amounts of dust and salt and for distinguishing different types of dust in ice relies on the accurate determination by a sensitive analytical technique (stable isotope dilution (SID) followed by thermal ionization mass spectrometry (TIMS)) of a suite of six major, minor, and trace alkali and alkaline earth metals (K, Rb, Cs, Ca, Sr, Ba). The geochemical abundances and behaviors of these metals are well known, and their proportions contrast between rock dust and sea salt. The metals vary between rock types to allow us to assign general sources of the dust. 18,487

Elemental composition determined by PIXE analysis of the insoluble aerosol particles in EPICA‐Dome C ice core samples representing the last 27000 years

“…The K concentrations (Figure 1b) are in agreement with the data given by Hinkley and Matsumoto [2001], for the Taylor Dome ice core (coastal West Antarctica).…”

Sediment flux through the McMurdo Ice Shelf in Windless Bight, Antarctica

“…By contrast, locations in Antarctica distant from sediment sources report modern/Holocene accumulation rates several orders of magnitude less (e.g. 0.001 g m − 2 year for Byrd Station; Windom (1969); and 0.009 g m − 2 year for Taylor Dome; Hinkley and Matsumoto, (2001)). Our calculated average accumulation rate of 0.80 g m − 2 year is consistent with sediment being derived from a local, rather than global, source.…”

Interpreting H2O isotope variations in high‐altitude ice cores using a cyclone model

“…On an interannual timescale this would interfere with the calibration of an isotopic thermometer such as was reported earlier by Dansgaard et al [1973] at altitudes below 1000 m on the Greenland ice sheet and as found for low‐altitude sites in Antarctica [e.g., Schlosser , 1999]. Interior sites would not necessarily be so affected at these timescales but under glacial conditions with more vigorous atmospheric circulation [ Petit et al , 1999; Bush and Philander , 1999; Hinkley and Matsumoto , 2001] the effects of a significant increase in size of cyclones on the isotopic thermometer would be widespread. As discussed in H08, moisture for such sites as Vostok is derived from cyclonic systems circling the continent within the CPLPZ.…”

“… Hansson [1995] quotes an estimated doubling of average wind speed at high latitudes during the Last Glacial Maximum (LGM). Certain types of ice core analyses [e.g., Hinkley and Matsumoto , 2001] while not yet quantitative in terms of climatic variables, do indicate significantly higher wind speeds during LG times. Evidence from extensive worldwide loess deposits and their deduced glacial source areas are consistent with the above evidence.…”