Data-constrained assessment of ocean circulation changes since the middle Miocene in an Earth system model
Since the middle Miocene (15 Ma, million years ago), the Earth's climate has undergone a long-term cooling trend, characterised by a reduction in ocean temperatures of up to 7–8 ∘ C . The causes of this cooling are primarily thought to be due to tectonic plate movements driving changes in large...
Published in: | Climate of the Past |
---|---|
Main Authors: | , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Copernicus Publications
2021
|
Subjects: | |
Online Access: | https://doi.org/10.5194/cp-17-2223-2021 https://doaj.org/article/5116be7b6d1d4a3b88ae6587ecfac3bc |
id |
ftdoajarticles:oai:doaj.org/article:5116be7b6d1d4a3b88ae6587ecfac3bc |
---|---|
record_format |
openpolar |
spelling |
ftdoajarticles:oai:doaj.org/article:5116be7b6d1d4a3b88ae6587ecfac3bc 2023-05-15T16:41:36+02:00 Data-constrained assessment of ocean circulation changes since the middle Miocene in an Earth system model K. A. Crichton A. Ridgwell D. J. Lunt A. Farnsworth P. N. Pearson 2021-10-01T00:00:00Z https://doi.org/10.5194/cp-17-2223-2021 https://doaj.org/article/5116be7b6d1d4a3b88ae6587ecfac3bc EN eng Copernicus Publications https://cp.copernicus.org/articles/17/2223/2021/cp-17-2223-2021.pdf https://doaj.org/toc/1814-9324 https://doaj.org/toc/1814-9332 doi:10.5194/cp-17-2223-2021 1814-9324 1814-9332 https://doaj.org/article/5116be7b6d1d4a3b88ae6587ecfac3bc Climate of the Past, Vol 17, Pp 2223-2254 (2021) Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 article 2021 ftdoajarticles https://doi.org/10.5194/cp-17-2223-2021 2022-12-31T14:49:06Z Since the middle Miocene (15 Ma, million years ago), the Earth's climate has undergone a long-term cooling trend, characterised by a reduction in ocean temperatures of up to 7–8 ∘ C . The causes of this cooling are primarily thought to be due to tectonic plate movements driving changes in large-scale ocean circulation patterns, and hence heat redistribution, in conjunction with a drop in atmospheric greenhouse gas forcing (and attendant ice-sheet growth and feedback). In this study, we assess the potential to constrain the evolving patterns of global ocean circulation and cooling over the last 15 Ma by assimilating a variety of marine sediment proxy data in an Earth system model. We do this by first compiling surface and benthic ocean temperature and benthic carbon-13 ( δ 13 C ) data in a series of seven time slices spaced at approximately 2.5 Myr intervals. We then pair this with a corresponding series of tectonic and climate boundary condition reconstructions in the cGENIE (“muffin” release) Earth system model, including alternative possibilities for an open vs. closed Central American Seaway (CAS) from 10 Ma onwards. In the cGENIE model, we explore uncertainty in greenhouse gas forcing and the magnitude of North Pacific to North Atlantic salinity flux adjustment required in the model to create an Atlantic Meridional Overturning Circulation (AMOC) of a specific strength, via a series of 12 (one for each tectonic reconstruction) 2D parameter ensembles. Each ensemble member is then tested against the observed global temperature and benthic δ 13 C patterns. We identify that a relatively high CO 2 equivalent forcing of 1120 ppm is required at 15 Ma in cGENIE to reproduce proxy temperature estimates in the model, noting that this CO 2 forcing is dependent on the cGENIE model's climate sensitivity and that it incorporates the effects of all greenhouse gases. We find that reproducing the observed long-term cooling trend requires a progressively declining greenhouse gas forcing in the model. In parallel to this, the ... Article in Journal/Newspaper Ice Sheet North Atlantic Directory of Open Access Journals: DOAJ Articles Pacific Climate of the Past 17 5 2223 2254 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 |
spellingShingle |
Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 K. A. Crichton A. Ridgwell D. J. Lunt A. Farnsworth P. N. Pearson Data-constrained assessment of ocean circulation changes since the middle Miocene in an Earth system model |
topic_facet |
Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 |
description |
Since the middle Miocene (15 Ma, million years ago), the Earth's climate has undergone a long-term cooling trend, characterised by a reduction in ocean temperatures of up to 7–8 ∘ C . The causes of this cooling are primarily thought to be due to tectonic plate movements driving changes in large-scale ocean circulation patterns, and hence heat redistribution, in conjunction with a drop in atmospheric greenhouse gas forcing (and attendant ice-sheet growth and feedback). In this study, we assess the potential to constrain the evolving patterns of global ocean circulation and cooling over the last 15 Ma by assimilating a variety of marine sediment proxy data in an Earth system model. We do this by first compiling surface and benthic ocean temperature and benthic carbon-13 ( δ 13 C ) data in a series of seven time slices spaced at approximately 2.5 Myr intervals. We then pair this with a corresponding series of tectonic and climate boundary condition reconstructions in the cGENIE (“muffin” release) Earth system model, including alternative possibilities for an open vs. closed Central American Seaway (CAS) from 10 Ma onwards. In the cGENIE model, we explore uncertainty in greenhouse gas forcing and the magnitude of North Pacific to North Atlantic salinity flux adjustment required in the model to create an Atlantic Meridional Overturning Circulation (AMOC) of a specific strength, via a series of 12 (one for each tectonic reconstruction) 2D parameter ensembles. Each ensemble member is then tested against the observed global temperature and benthic δ 13 C patterns. We identify that a relatively high CO 2 equivalent forcing of 1120 ppm is required at 15 Ma in cGENIE to reproduce proxy temperature estimates in the model, noting that this CO 2 forcing is dependent on the cGENIE model's climate sensitivity and that it incorporates the effects of all greenhouse gases. We find that reproducing the observed long-term cooling trend requires a progressively declining greenhouse gas forcing in the model. In parallel to this, the ... |
format |
Article in Journal/Newspaper |
author |
K. A. Crichton A. Ridgwell D. J. Lunt A. Farnsworth P. N. Pearson |
author_facet |
K. A. Crichton A. Ridgwell D. J. Lunt A. Farnsworth P. N. Pearson |
author_sort |
K. A. Crichton |
title |
Data-constrained assessment of ocean circulation changes since the middle Miocene in an Earth system model |
title_short |
Data-constrained assessment of ocean circulation changes since the middle Miocene in an Earth system model |
title_full |
Data-constrained assessment of ocean circulation changes since the middle Miocene in an Earth system model |
title_fullStr |
Data-constrained assessment of ocean circulation changes since the middle Miocene in an Earth system model |
title_full_unstemmed |
Data-constrained assessment of ocean circulation changes since the middle Miocene in an Earth system model |
title_sort |
data-constrained assessment of ocean circulation changes since the middle miocene in an earth system model |
publisher |
Copernicus Publications |
publishDate |
2021 |
url |
https://doi.org/10.5194/cp-17-2223-2021 https://doaj.org/article/5116be7b6d1d4a3b88ae6587ecfac3bc |
geographic |
Pacific |
geographic_facet |
Pacific |
genre |
Ice Sheet North Atlantic |
genre_facet |
Ice Sheet North Atlantic |
op_source |
Climate of the Past, Vol 17, Pp 2223-2254 (2021) |
op_relation |
https://cp.copernicus.org/articles/17/2223/2021/cp-17-2223-2021.pdf https://doaj.org/toc/1814-9324 https://doaj.org/toc/1814-9332 doi:10.5194/cp-17-2223-2021 1814-9324 1814-9332 https://doaj.org/article/5116be7b6d1d4a3b88ae6587ecfac3bc |
op_doi |
https://doi.org/10.5194/cp-17-2223-2021 |
container_title |
Climate of the Past |
container_volume |
17 |
container_issue |
5 |
container_start_page |
2223 |
op_container_end_page |
2254 |
_version_ |
1766032057653264384 |