Atmospheric ¹⁰Be in an Antarctic soil: Implications for climate change

Abstract

[1] Concentrations of 10 Be, 9 Be, and salt in a soil profile from the lower Wright Valley reveal two distinct climatic regimes. In the upper horizon of the soil profile, a thin gravel lag overlies the Hart ash (3.9 ± 0.3 Ma), and this sits on the surface of a well-developed paleosol, which makes up the lower horizon of the profile. The surface lag has a smaller inventory of 10 Be than predicted from the fallout rate at nearby Taylor Dome. Below the gravel, the Hart ash is virtually devoid of 10 Be and the calculated erosion rate for the gravel-ash horizon is 2.8 m Ma À1 . The paleosol, which has been sealed by the overlying ash, has a relatively high inventory of 10 Be, and this gives it a significantly lower erosion rate (0.5 m Ma À1 ) than the gravel-ash horizon. Beryllium-10 migrates into a soil profile either by solution transport or by fine-particle translocation. The lack of 10 Be in the Hart ash indicates that neither of these processes have been active at this site for the past 3.9 Ma. However, enrichment of 10 Be in the paleosol indicates they were active prior to deposition of the ash. The most likely reason these processes were active is that there was more water, which could translocate fine particles with attached 10 Be. Thus, the gravel-ash horizon developed in climatic conditions similar to the present, while the paleosol developed in wetter and possibly warmer conditions during the early Pliocene and possibly before that time.

Quantifying regolith erosion rates with cosmogenic nuclides 10Be and 26Al in the McMurdo Dry Valleys, Antarctica

“…Putkonen et al [2008] found that a landslide deposit in Arena Valley was eroding at a rate of 2.1 m Ma −1 for at least the past ∼2 Ma, which is an order of magnitude higher than the erosion rate at the Arena Valley ash site determined in this study. At the Hart ash site, the results are consistent with those found by Schiller et al [2009], who used atmospherically produced 10 Be to determine erosion rates of only 0.5 m Ma −1 before the Hart ash was deposited and 2.8 m Ma −1 after the ash was deposited.…”

Reprint of: Late Neogene climate and glacial history of the Southern Victoria Land coast from integrated drill core, seismic and outcrop data

“…Late Pliocene cooling, re-advance of the WAIS, and transition to coldbased terrestrial glaciers A relatively thick diatomite sequence in the AND-1B core, which was deposited between 3.6 and 3.4 Ma, indicates that warmer-than-present conditions persisted in the western Ross Sea into the early late Pliocene. However, a cooling trend is reflected in diatom assemblage data (Winter et al, 2010b) and deposits in the Dry Valleys indicate increasing aridity and decrease in available meltwater after 3.9 Ma (Schiller et al, 2009). Integrated geological data examined in this study indicate that this early late Pliocene cooling trend led to a major climate/glacial transition beginning at~3.4 Ma.…”

Linking ice sheet and lake sediment archives of 10Be, 1468–1980 CE

“…The isotope production rate is not linearly related to solar activity variations, however, and also varies with altitude and latitude [1,2]. Variability in pathways from atmospheric production to terrestrial deposition further complicates the link between 10 Be production and its occurrence in natural archives. Therefore, it is of high interest to attain 10 Be data from different types of archives, as well as from a range of geographic locations.…”

“…Variability in pathways from atmospheric production to terrestrial deposition further complicates the link between 10 Be production and its occurrence in natural archives. Therefore, it is of high interest to attain 10 Be data from different types of archives, as well as from a range of geographic locations. So far, atmospherically produced 10 Be has been measured in glacial ice [3,4] and deep sea sediments [5], as well as in contemporary precipitation [6,7] and aerosols [8].…”

“…The prevalence of 10 Be is linked to past solar activity through the Sun's modulation of cosmic ray incidence on the Earth atmosphere. The isotope production rate is not linearly related to solar activity variations, however, and also varies with altitude and latitude [1,2].…”