the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 29 Jul 2024
Observed bottom warming in the East Siberian Sea driven by the intensified vertical mixing
Abstract. The East Siberian Sea has the broadest continental shelf on Earth and nearly 80 % of the subsea permafrost worldwide. There exists a cold layer with the temperature at freezing points around −1.5 ºC above the sea floor of the shelf, preventing the heat transport from above to melt the permafrost and release the methane from sediments. However, we observed a worrying warming trend at the seafloor caused by enhanced vertical mixing in the shelf of the East Siberian Sea. In an ice-reduced Arctic continental shelf, even a moderate cyclone can result in the rapid growth of high wave to stir the marginal sea uniformly, which is not observed before. The intensified mixing can transport enormous heat downward, leading to a remarkable warming of more than 3 °C at the bottom. As the Arctic is experiencing accelerated warming and the sea ice is rapidly retreating, the East Siberian Sea will undoubtedly suffer more extreme heatwaves, which might cause unpredictable climate impacts on the Arctic biochemical processes and greenhouse gas emission.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
(3581 KB)
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(3581 KB) - Metadata XML
- BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
The East Siberian Sea has nearly 80 % of the subsea permafrost worldwide. The cold layer with a temperature around −1.5 ºC above the seafloor prevents heat transporting from above to melt permafrost and release methane from sediments. However, we observed a warming trend at the seafloor caused by wave-induced vertical mixing in the shelf. The intensified mixing can transport enormous heat downward, leading to warming of more than 3 °C at the bottom, putting the subsea permafrost at high risk.
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2024-2271', Anonymous Referee #1, 12 Aug 2024
This ms tackles and important topic - the warming of deep water in the shelf seas around the Arctic Ocean and by implication the potential impact on the melting of methane hydrates. The paper essentially proposes that increased open water leads to more momentum transfer to TKE and so mixing via larger storm generated surface waves. Whilst there is good published evidence to support the more open water, more mixing due to storms hypothesis (eg. Polyakov et al, 2020, https://doi.org/10.1029/2020GL089469; Rippeth and Fines, 2022, https://doi.org/10.5670/oceanog.2022.103) different mechanisms are invoked. The authors do not consider these alternatives and so the final step in their argument, ie. more mixing via a more vigorous wave field is not proven as the paper stands.
These mechanisms include wind triggered inertial oscillations, eg in the Laptev Sea under under both open water and sea ice conditions (Lenn et al., 2011, https://doi.org/10.1175/2010JPO4425.1). Note as shown in this paper the mixing is intermittent with short term events dominating the downward heat flux (how do these heat fluxes compare to those in line 155). The same wind shear alignment mechanism can also drive the deepening of the surface mixed layer (Lincoln et al., https://doi.org/10.1002/2015JC011382).
Also, the development of continental shelf waves trigger by remote storms which drive periods of intense mixing. See (Schulz et al., 2021, http://10.1029/2021GL092988).
A few minor points:
line 26: do you mean "increasing down" mixing of heat? 27-28: a citation is required. Is the 'dramatic and abrupt' warming due to complete mixing of the water column (more likely than diapcynal mixing)?
32: citation required.
41-42: I assume that the: "during this period" are your original observations - this needs to be made clearer. Figure 1e - there is no label on the x-axis to say what the numbers refer to?
126: "previous studies" needs a citation to direct to the pervious studies?
155: Heat flux - how does this compare to others on the Arctic continental shelf?
Figure 3: I am not clear on what the geostrophic currents are showing?
Citation: https://doi.org/10.5194/egusphere-2024-2271-RC1 -
AC1: 'Reply on RC1', Xianyao Chen, 28 Oct 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2271/egusphere-2024-2271-AC1-supplement.pdf
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AC1: 'Reply on RC1', Xianyao Chen, 28 Oct 2024
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RC2: 'Comment on egusphere-2024-2271', Anonymous Referee #2, 03 Sep 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2271/egusphere-2024-2271-RC2-supplement.pdf
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AC2: 'Reply on RC2', Xianyao Chen, 28 Oct 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2271/egusphere-2024-2271-AC2-supplement.pdf
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AC2: 'Reply on RC2', Xianyao Chen, 28 Oct 2024
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2024-2271', Anonymous Referee #1, 12 Aug 2024
This ms tackles and important topic - the warming of deep water in the shelf seas around the Arctic Ocean and by implication the potential impact on the melting of methane hydrates. The paper essentially proposes that increased open water leads to more momentum transfer to TKE and so mixing via larger storm generated surface waves. Whilst there is good published evidence to support the more open water, more mixing due to storms hypothesis (eg. Polyakov et al, 2020, https://doi.org/10.1029/2020GL089469; Rippeth and Fines, 2022, https://doi.org/10.5670/oceanog.2022.103) different mechanisms are invoked. The authors do not consider these alternatives and so the final step in their argument, ie. more mixing via a more vigorous wave field is not proven as the paper stands.
These mechanisms include wind triggered inertial oscillations, eg in the Laptev Sea under under both open water and sea ice conditions (Lenn et al., 2011, https://doi.org/10.1175/2010JPO4425.1). Note as shown in this paper the mixing is intermittent with short term events dominating the downward heat flux (how do these heat fluxes compare to those in line 155). The same wind shear alignment mechanism can also drive the deepening of the surface mixed layer (Lincoln et al., https://doi.org/10.1002/2015JC011382).
Also, the development of continental shelf waves trigger by remote storms which drive periods of intense mixing. See (Schulz et al., 2021, http://10.1029/2021GL092988).
A few minor points:
line 26: do you mean "increasing down" mixing of heat? 27-28: a citation is required. Is the 'dramatic and abrupt' warming due to complete mixing of the water column (more likely than diapcynal mixing)?
32: citation required.
41-42: I assume that the: "during this period" are your original observations - this needs to be made clearer. Figure 1e - there is no label on the x-axis to say what the numbers refer to?
126: "previous studies" needs a citation to direct to the pervious studies?
155: Heat flux - how does this compare to others on the Arctic continental shelf?
Figure 3: I am not clear on what the geostrophic currents are showing?
Citation: https://doi.org/10.5194/egusphere-2024-2271-RC1 -
AC1: 'Reply on RC1', Xianyao Chen, 28 Oct 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2271/egusphere-2024-2271-AC1-supplement.pdf
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AC1: 'Reply on RC1', Xianyao Chen, 28 Oct 2024
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RC2: 'Comment on egusphere-2024-2271', Anonymous Referee #2, 03 Sep 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2271/egusphere-2024-2271-RC2-supplement.pdf
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AC2: 'Reply on RC2', Xianyao Chen, 28 Oct 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2271/egusphere-2024-2271-AC2-supplement.pdf
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AC2: 'Reply on RC2', Xianyao Chen, 28 Oct 2024
Peer review completion
Journal article(s) based on this preprint
The East Siberian Sea has nearly 80 % of the subsea permafrost worldwide. The cold layer with a temperature around −1.5 ºC above the seafloor prevents heat transporting from above to melt permafrost and release methane from sediments. However, we observed a warming trend at the seafloor caused by wave-induced vertical mixing in the shelf. The intensified mixing can transport enormous heat downward, leading to warming of more than 3 °C at the bottom, putting the subsea permafrost at high risk.
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Xiaoyu Wang
Longjiang Mu
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(3581 KB) - Metadata XML
The East Siberian Sea has nearly 80% of the subsea permafrost worldwide. The cold layer with a temperature around −1.5 ºC above the sea floor prevents heat transporting from above to melt permafrost and release methane from sediments. However, we observed a warming trend at the seafloor caused by wave-induced vertical mixing in the shelf. The intensified mixing can transport enormous heat downward, leading to warming of more than 3 °C at the bottom, putting the subsea permafrost in high risk.
The East Siberian Sea has nearly 80% of the subsea permafrost worldwide. The cold layer with a...