ORCID Profile
0000-0002-2266-5551
Current Organisation
Trinity College Dublin
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Publisher: Research Square Platform LLC
Date: 08-02-2022
DOI: 10.21203/RS.3.RS-1307003/V1
Abstract: Standard proxies for reconstructing surface mass balance (SMB) in Antarctic ice cores are often inaccurate or coarsely resolved when applied to more complicated environments away from dome summits. Here, we propose an alternative SMB proxy based on photolytic fractionation of nitrogen isotopes in nitrate observed at 114 sites throughout East Antarctica. Applying this proxy approach to nitrate in a shallow core drilled at a moderate SMB site (Aurora Basin North), we reconstruct 700 years of SMB changes that agree well with changes estimated from ice core density and upstream surface topography. For the under-s led transition zones between dome summits and the coast, this proxy can considerably expand our SMB records by providing high-resolution SMBs that better reflect the local environment and are easier to s le than existing techniques. One Sentence Summary: Nitrate isotopes offer a new way to track past and present changes in Antarctic snowfall and ice sheet mass balance.
Publisher: Elsevier BV
Date: 2014
Publisher: SAGE Publications
Date: 04-2019
Abstract: Social and environmental changes had great spatiotemporal variability in the Maya Lowlands during the Classic and Postclassic Periods, and stalagmites promise high-resolution paleoclimate data that can refine our understanding of this complex time. Unfortunately, stalagmites in this region are often difficult to date by U-Th methods because of low initial uranium concentrations. Other dating techniques can be used on such stalagmites, and we present here an age–depth model for BZBT1, a low-uranium stalagmite s led from Box Tunich cave in the Belize River Valley. This age–depth model dates the growth of BZBT1 to between 400 and 1610 yr BP (340–1550 CE) by combining evidence from U-Th results, radiocarbon dating of both stalagmite CaCO 3 and trapped organic material, and 210 Pb dating. The resulting stable isotope record from BZBT1 reveals paleoclimate changes that affected local Maya populations during the Classic and early Postclassic Periods. This record is further refined by isotopically tuning the BZBT1 data with two other regional stalagmite records. Our work offers additional paleoclimate insight into the relationship between the Maya and their environment from a stalagmite that would typically be disregarded for research purposes. Continued research into alternative dating techniques for speleothems can enable additional scientific discovery while promoting speleothem conservation.
Publisher: Elsevier BV
Date: 10-2016
Publisher: Springer Science and Business Media LLC
Date: 25-07-2022
DOI: 10.1038/S41467-022-31855-7
Abstract: Standard proxies for reconstructing surface mass balance (SMB) in Antarctic ice cores are often inaccurate or coarsely resolved when applied to more complicated environments away from dome summits. Here, we propose an alternative SMB proxy based on photolytic fractionation of nitrogen isotopes in nitrate observed at 114 sites throughout East Antarctica. Applying this proxy approach to nitrate in a shallow core drilled at a moderate SMB site (Aurora Basin North), we reconstruct 700 years of SMB changes that agree well with changes estimated from ice core density and upstream surface topography. For the under-s led transition zones between dome summits and the coast, we show that this proxy can provide past and present SMB values that reflect the immediate local environment and are derived independently from existing techniques.
Publisher: Copernicus GmbH
Date: 03-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-672
Abstract: & & Precise Antarctic snow accumulation estimates are needed to understand past and future changes in global sea levels, but standard reconstructions using water isotopes suffer from competing isotopic effects external to accumulation. We present here an alternative accumulation proxy based on the post-depositional photolytic fractionation of nitrogen isotopes (d& sup& & /sup& N) in nitrate. On the high plateau of East Antarctica, sunlight penetrating the uppermost snow layers converts snow-borne nitrate into nitrogen oxide gas that can be lost to the atmosphere. This nitrate loss favors & sup& & /sup& NO& sub& & /sub& & sup& -& /sup& over & sup& & /sup& NO& sub& & /sub& & sup& -& /sup& , and thus the d& sup& & /sup& N of nitrate remaining in the snow will steadily increase until the nitrate is eventually buried beneath the reach of light. Because the duration of time until burial is dependent upon the rate of net snow accumulation, sites with lower accumulation rates have a longer burial wait and thus higher d& sup& & /sup& N values. A linear relationship (r& sup& & /sup& = 0.86) between d& sup& & /sup& N and net accumulation& sup& -1& /sup& is calculated from over 120 s les representing 105 sites spanning East Antarctica. These sites largely encompass the full range of snow accumulation rates observed in East Antarctica, from 25 kg m-& sup& & /sup& yr& sup& -1& /sup& at deep interior sites to & kg m-& sup& & /sup& yr& sup& -1& /sup& at near coastal sites. We apply this relationship as a transfer function to an Aurora Basin ice core to produce a 700-year record of accumulation changes. Our nitrate-based estimate compares very well with a parallel reconstruction for Aurora Basin that uses volcanic horizons and ice-penetrating radar. Continued improvements to our database may enable precise independent estimates of millennial-scale accumulation changes using deep ice cores such as EPICA Dome C and Beyond EPICA-Oldest Ice.& &
No related grants have been discovered for Pete D. Akers.