Showing papers by "Todd Sowers published in 2016"
Paul Scherrer Institute1, Desert Research Institute2, University of Copenhagen3, Dartmouth College4, University of California, Berkeley5, Purdue University6, Lund University7, New Mexico Institute of Mining and Technology8, Curtin University9, Lamont–Doherty Earth Observatory10, University of Cambridge11, Pennsylvania State University12
TL;DR: This article presented the WD2014 chronology for the upper part of the West Antarctic Ice Sheet (WAIS) Divide (WD) ice core, which is based on counting of annual layers observed in the chemical, dust and electrical conductivity records.
Abstract: . We present the WD2014 chronology for the upper part (0–2850 m; 31.2 ka BP) of the West Antarctic Ice Sheet (WAIS) Divide (WD) ice core. The chronology is based on counting of annual layers observed in the chemical, dust and electrical conductivity records. These layers are caused by seasonal changes in the source, transport, and deposition of aerosols. The measurements were interpreted manually and with the aid of two automated methods. We validated the chronology by comparing to two high-accuracy, absolutely dated chronologies. For the Holocene, the cosmogenic isotope records of 10Be from WAIS Divide and 14C for IntCal13 demonstrated that WD2014 was consistently accurate to better than 0.5 % of the age. For the glacial period, comparisons to the Hulu Cave chronology demonstrated that WD2014 had an accuracy of better than 1 % of the age at three abrupt climate change events between 27 and 31 ka. WD2014 has consistently younger ages than Greenland ice core chronologies during most of the Holocene. For the Younger Dryas–Preboreal transition (11.595 ka; 24 years younger) and the Bolling–Allerod Warming (14.621 ka; 7 years younger), WD2014 ages are within the combined uncertainties of the timescales. Given its high accuracy, WD2014 can become a reference chronology for the Southern Hemisphere, with synchronization to other chronologies feasible using high-quality proxies of volcanism, solar activity, atmospheric mineral dust, and atmospheric methane concentrations.
167 citations
TL;DR: In this paper, the authors used high-resolution geochemical and microbiological approaches to examine the N2O concentrations, the quantitative distributions of dust, Ca+2, NH4+ and NO3− ions related to N cycle pathways, the microbial abundance and diversity at specific NEEM core depths from 1758m to 1867m.
Abstract: Deep polar ice cores provide atmospheric records of nitrous oxide (N2O) and other trace gases reflecting climate history along with a parallel archive of microbial cells transported with mineral dust, marine and volcanic aerosols from around the globe. Our interdisciplinary study of 32 samples from different depths of the recently drilled NEEM Greenland ice core addressed the question whether the identified microorganisms were capable of post-depositional biological production of N2O in situ. We used high-resolution geochemical and microbiological approaches to examine the N2O concentrations, the quantitative distributions of dust, Ca+2, NH4+ and NO3− ions related to N cycle pathways, the microbial abundance and diversity at specific NEEM core depths from 1758 m to 1867.8 m. Results showed varying concentrations of N2O (220–271.5 ppb). Microbial abundance fluctuated between 3.3 × 104 and 3.3 × 106 cells mL−1 in direct correlation with dust and Ca2+ concentrations with higher cell numbers deposited...
17 citations