ORCID Profile
0000-0002-0430-5720
Current Organisation
Oregon State University
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Publisher: Copernicus GmbH
Date: 23-03-2022
Publisher: Copernicus GmbH
Date: 10-08-2022
Abstract: Abstract. A new ice core was drilled in West Antarctica on Skytrain Ice Rise in field season 2018/2019. This 651 m ice core is one of the main targets of the WACSWAIN (WArm Climate Stability of the West Antarctic ice sheet in the last INterglacial) project. A present-day accumulation rate of 13.5 cm w.e. yr−1 was derived. Although the project mainly aims to investigate the last interglacial (115–130 ka), a robust chronology period covering the recent past is needed to constrain the age models for the deepest ice. Additionally, this time period is important for understanding current climatic changes in the West Antarctic region. Here, we present a stratigraphic chronology for the top 184.14 m of the Skytrain ice core based on absolute age tie points interpolated using annual layer counting encompassing the last 2000 years of climate history. Together with a model-based depth–age relationship of the deeper part of the ice core, this will form the ST22 chronology. The chemical composition, dust content, liquid conductivity, water isotope concentration and methane content of the whole core was analysed via continuous flow analysis (CFA) at the British Antarctic Survey. Annual layer counting was performed by manual counting of seasonal variations in mainly the sodium and calcium records. This counted chronology was informed and anchored by absolute age tie points, namely, the tritium peak (1965 CE) and six volcanic eruptions. Methane concentration variations were used to further constrain the counting error. A minimal error of ±1 year at the tie points was derived, accumulating to ± 5 %–10 % of the age in the unconstrained sections between tie points. This level of accuracy enables data interpretation on at least decadal timescales and provides a solid base for the dating of deeper ice, which is the second part of the chronology.
Publisher: Copernicus GmbH
Date: 23-03-2022
DOI: 10.5194/CP-2022-28
Abstract: Abstract. A new ice core was drilled in West Antarctica on Skytrain Ice Rise in field season 2018 / 2019. This 651 m ice core is one of the main targets of the WACSWAIN (WArm Climate Stability of the West Antarctic ice sheet in the last INterglacial) project. A present-day accumulation rate of 13.5 cm w.e./year was derived. Although the project mainly aims to investigate the last interglacial (115–130 ka BP), a robust chronology period covering the recent past is needed to constrain the age models for the deepest ice. Additionally, this time period is important for understanding current climatic changes in theWest Antarctic region. Here, we present a stratigraphic chronology for the top 184.14 m of the Skytrain ice core covering the last 2000 years based on absolute age tie points interpolated using annual layer counting encompassing the last 2000 years of climate history. Together with a model-based depth-age relationship of the deeper part of the ice core, this will form the ST22 chronology. The chemical composition, dust content, liquid conductivity, water isotope concentration and methane content of the whole core was analysed via continuous flow analysis (CFA) at the British Antarctic Survey. Annual layer counting was performed by manual counting of seasonal variations in mainly the sodium and calcium records. This counted chronology was informed and anchored by absolute age tie points, namely, the tritium peak (1965 CE) and six volcanic eruptions. Methane concentration variations were used to further constrain the counting error. A minimal error of ± 1 year at the tie points was derived, accumulating to ± 5–10 % of the age in the unconstrained sections between tie points. This level of accuracy enables data interpretation on at least decadal timescales and provides a solid base for the dating of deeper ice, which is the second part of the chronology.
Publisher: Copernicus GmbH
Date: 27-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-2075
Abstract: & & We present new measurements of methane (CH4) and carbon dioxide (CO2) in the Skytrain ice core, with gas ages dated around 1610AD. The aim of these measurements is to improve our understanding of why there is a significant difference between measured CO2 at that time in current ice core records.& & & & A pronounced feature of the Law Dome record (accumulation 60 cm ice eq. yr gas age distribution 8 years,) is a rapid decrease in CO2 of ~10 ppm over 50 years with a distinct minimum at 1610. The cause of this decrease is much debated, with complex carbon cycle feedbacks required in explanation. However, other ice cores do not show the same event. The West Antarctic Ice Sheet (WAIS) ide record (accumulation 22 cm ice eq. yr gas age distribution 19 years) shows a steadier decline in CO2 of approximately 6 ppm over the same period, with the record also ~2-3 ppm higher than Law Dome throughout 900-1800 CE. A follow-up study using the Dronning Maud Land (DML) ice core (accumulation 7 cm ice eq. yr gas age distribution 65 years) attempted to prove which core showed the real atmospheric signal, but results were inconclusive due to the wide gas-age distribution of the record. While Skytrain (accumulation 14 cm ice eq. yr) does not match the accumulation rate of Law Dome, we present these new, high-resolution gas measurements over the period to work towards answering the following questions: (1) if the Law Dome record is correct, what caused this litude of CO2 change over a short timescale? (2) Does one of the records suffer from contamination? (3) Is our understanding of gas smoothing processes in these ice cores inaccurate? We will then use these measurements, from a well-validated & #8216 needle-crusher& #8217 CO2 device at the ice core labs at Oregon State University, USA, to validate a new semi-continuous ice-grating device (for which we present a preliminary outline) at the new ice core gas analysis lab at the British Antarctic Survey, UK.& &
No related grants have been discovered for Jenna Epifanio.