Mysteriously high I14C of the glacial atmosphere : Influence of 14C production and carbon cycle changes
(2020) In Climate of the Past 16(4). p.1159-1185- Abstract
Despite intense focus on the span classCombining double low lineinline-formulag1/4190/span drop in atmospheric span classCombining double low lineinline-formulaI14C/span during Heinrich Stadial 1 at span classCombining double low lineinline-formulag1/417.4/span-14.6 span classCombining double low lineinline-formulaka/span, the specific mechanisms responsible for the apparent span classCombining double low lineinline-formulaI14C/span excess in the glacial atmosphere have received considerably less attention. The computationally efficient Bern3D Earth system model of intermediate complexity, designed for long-term climate simulations, allows us to address a very fundamental but still elusive question concerning the atmospheric span... (More)
Despite intense focus on the span classCombining double low lineinline-formulag1/4190/span drop in atmospheric span classCombining double low lineinline-formulaI14C/span during Heinrich Stadial 1 at span classCombining double low lineinline-formulag1/417.4/span-14.6 span classCombining double low lineinline-formulaka/span, the specific mechanisms responsible for the apparent span classCombining double low lineinline-formulaI14C/span excess in the glacial atmosphere have received considerably less attention. The computationally efficient Bern3D Earth system model of intermediate complexity, designed for long-term climate simulations, allows us to address a very fundamental but still elusive question concerning the atmospheric span classCombining double low lineinline-formulaI14C/span record: how can we explain the persistence of relatively high span classCombining double low lineinline-formulaI14C/span values during the millennia after the Laschamp event? Large uncertainties in the pre-Holocene span classCombining double low lineinline-formula14C/span production rate, as well as in the older portion of the span classCombining double low lineinline-formulaI14C/span record, complicate our qualitative and quantitative interpretation of the glacial span classCombining double low lineinline-formulaI14C/span elevation. Here we begin with sensitivity experiments that investigate the controls on atmospheric span classCombining double low lineinline-formulaI14C/span in idealized settings. We show that the interaction with the ocean sediments may be much more important to the simulation of span classCombining double low lineinline-formulaI14C/span than had been previously thought. In order to provide a bounded estimate of glacial span classCombining double low lineinline-formulaI14C/span change, the Bern3D model was integrated with five available estimates of the span classCombining double low lineinline-formula14C/span production rate as well as reconstructed and hypothetical paleoclimate forcing. Model results demonstrate that none of the available reconstructions of past changes in span classCombining double low lineinline-formula14C/span production can reproduce the elevated span classCombining double low lineinline-formulaI14C/span levels during the last glacial. In order to increase atmospheric span classCombining double low lineinline-formulaI14C/span to glacial levels, a drastic reduction of air-sea exchange efficiency in the polar regions must be assumed, though discrepancies remain for the portion of the record younger than span classCombining double low lineinline-formulag1/433/span span classCombining double low lineinline-formulaka/span. We end with an illustration of how the span classCombining double low lineinline-formula14C/span production rate would have had to evolve to be consistent with the span classCombining double low lineinline-formulaI14C/span record by combining an atmospheric radiocarbon budget with the Bern3D model. The overall conclusion is that the remaining discrepancies with respect to glacial span classCombining double low lineinline-formulaI14C/span may be linked to an underestimation of span classCombining double low lineinline-formula14C/span production and/or a biased-high reconstruction of span classCombining double low lineinline-formulaI14C/span over the time period of interest. Alternatively, we appear to still be missing an important carbon cycle process for atmospheric span classCombining double low lineinline-formulaI14C/span.
(Less)
- author
- Dinauer, Ashley ; Adolphi, Florian LU and Joos, Fortunat
- organization
- publishing date
- 2020-07-09
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Climate of the Past
- volume
- 16
- issue
- 4
- pages
- 27 pages
- publisher
- Copernicus GmbH
- external identifiers
-
- scopus:85089406613
- ISSN
- 1814-9324
- DOI
- 10.5194/cp-16-1159-2020
- language
- English
- LU publication?
- yes
- id
- bd441baa-6e99-4edc-9deb-9a631152ecc0
- date added to LUP
- 2021-01-12 10:55:47
- date last changed
- 2022-04-26 23:24:25
@article{bd441baa-6e99-4edc-9deb-9a631152ecc0,
abstract = {{<p>Despite intense focus on the span classCombining double low lineinline-formulag1/4190/span drop in atmospheric span classCombining double low lineinline-formulaI14C/span during Heinrich Stadial 1 at span classCombining double low lineinline-formulag1/417.4/span-14.6 span classCombining double low lineinline-formulaka/span, the specific mechanisms responsible for the apparent span classCombining double low lineinline-formulaI14C/span excess in the glacial atmosphere have received considerably less attention. The computationally efficient Bern3D Earth system model of intermediate complexity, designed for long-term climate simulations, allows us to address a very fundamental but still elusive question concerning the atmospheric span classCombining double low lineinline-formulaI14C/span record: how can we explain the persistence of relatively high span classCombining double low lineinline-formulaI14C/span values during the millennia after the Laschamp event? Large uncertainties in the pre-Holocene span classCombining double low lineinline-formula14C/span production rate, as well as in the older portion of the span classCombining double low lineinline-formulaI14C/span record, complicate our qualitative and quantitative interpretation of the glacial span classCombining double low lineinline-formulaI14C/span elevation. Here we begin with sensitivity experiments that investigate the controls on atmospheric span classCombining double low lineinline-formulaI14C/span in idealized settings. We show that the interaction with the ocean sediments may be much more important to the simulation of span classCombining double low lineinline-formulaI14C/span than had been previously thought. In order to provide a bounded estimate of glacial span classCombining double low lineinline-formulaI14C/span change, the Bern3D model was integrated with five available estimates of the span classCombining double low lineinline-formula14C/span production rate as well as reconstructed and hypothetical paleoclimate forcing. Model results demonstrate that none of the available reconstructions of past changes in span classCombining double low lineinline-formula14C/span production can reproduce the elevated span classCombining double low lineinline-formulaI14C/span levels during the last glacial. In order to increase atmospheric span classCombining double low lineinline-formulaI14C/span to glacial levels, a drastic reduction of air-sea exchange efficiency in the polar regions must be assumed, though discrepancies remain for the portion of the record younger than span classCombining double low lineinline-formulag1/433/span span classCombining double low lineinline-formulaka/span. We end with an illustration of how the span classCombining double low lineinline-formula14C/span production rate would have had to evolve to be consistent with the span classCombining double low lineinline-formulaI14C/span record by combining an atmospheric radiocarbon budget with the Bern3D model. The overall conclusion is that the remaining discrepancies with respect to glacial span classCombining double low lineinline-formulaI14C/span may be linked to an underestimation of span classCombining double low lineinline-formula14C/span production and/or a biased-high reconstruction of span classCombining double low lineinline-formulaI14C/span over the time period of interest. Alternatively, we appear to still be missing an important carbon cycle process for atmospheric span classCombining double low lineinline-formulaI14C/span. </p>}},
author = {{Dinauer, Ashley and Adolphi, Florian and Joos, Fortunat}},
issn = {{1814-9324}},
language = {{eng}},
month = {{07}},
number = {{4}},
pages = {{1159--1185}},
publisher = {{Copernicus GmbH}},
series = {{Climate of the Past}},
title = {{Mysteriously high I14C of the glacial atmosphere : Influence of 14C production and carbon cycle changes}},
url = {{http://dx.doi.org/10.5194/cp-16-1159-2020}},
doi = {{10.5194/cp-16-1159-2020}},
volume = {{16}},
year = {{2020}},
}