the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 04 Jan 2023
Sudden, local temperature increase above the continental slope in the Southern Weddell Sea, Antarctica
Abstract. Around most of Antarctica, the Circumpolar Deep Water (CDW) shows a warming trend. At the same time, the thermocline is shoaling, thereby increasing the potential for CDW to enter the shallow continental shelves and ultimately increase basal melt in the ice shelf cavities that line the coast. Similar trends, on the order of 0.05 °C and 30 m per decade, have been observed in the Warm Deep Water (WDW), the slightly cooled CDW derivative found at depth in the Weddell Sea. Here we report on a sudden, local increase in the temperature maximum of the WDW above the continental slope north of the Filchner Trough (25–40° W), a region identified as a hotspot for potential changes in the flow of WDW towards the large Filchner-Ronne Ice Shelf. A combination of new and historical Conductivity-Temperature-Depth profiles and mooring records show that, starting in late 2019, the temperature of the warm water core increased by about 0.1 °C over the upper part of the slope (700–2750 m depth). The increased temperature of the WDW is accompanied by an unprecedented (in observations) freshening of about 0.1 g kg-1 in the overlying Winter Water. Mooring records from the continental shelf further south, in the inflow pathway, do not show increased temperatures during the same period, suggesting that factors other than the WDW core temperature over the slope determine the variability in the heat content on the shelf.
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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
(10866 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
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- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2022-1477', Karen J. Heywood, 12 Feb 2023
I enjoyed reading this paper. It is well written, clearly presented and interesting, with some ingenious analyses. The figures are very good. A particular strength is the analysis of an excellent long-term climatology that has been carefully assembled of ship, seal and float profiles in a region where there have been relatively few studies. It also presents unusually long time series from moorings near the Filchner Ronne Ice Shelf and on the continental shelf and slope. The paper discusses temporal variability, and in particular, possible causes and implications of an occurrence of surprisingly warm WDW in 2021. I found the estimates of the possible impact on AABW very interesting.
I am happy to recommend acceptance of the paper subject to consideration of some minor suggestions that I list below.
The abstract is nice, but it doesn’t really do justice to the conclusions you came to about the importance of the observed warming, for example for eventual AABW properties. It would be good to include these implications in the abstract.
L17 I wouldn’t say that the Amundsen Sea has a narrow continental shelf – it is hundreds of km from the shelf break to the vulnerable glaciers such as Pine Island and Thwaites.
L23 include a reference to moderate melt rates for FRIS?
L27 typo – you mean tenths not tens of a degree, I think.
L41 I had to read the bit after the Nicholls reference several times, as it’s difficult to make out with the commas and references breaking it up. Try to rephrase to make it easier for readers?
L54 I was curious what the source was of the remaining profiles out of the >1000 that are not ship or seals! Later on it’s clear that these are profiling floats – I would state that here. Also I recommend giving a reference to MEOP to give due credit to those assembling MEOP data – information about how to cite the data is here https://www.meop.net/database/how-to-cite.html.
Probably there is a similar reference to duly acknowledge the efforts of those assembling the Argo float data set? Both these data sources should be cited in the text as well as incldued in the data section at the end.
L64 what is OTE? Expand?
Caption to Figure 2. I get that the mentions of 1515 m depth and the 1300-1700m depth range are referring to the sea bed depth, but maybe that needs to be spelt out more clearly?
L106 and L108 Are these references to the same paper? In review? 2023? Reference list says in prep?
L116 The in review reference should be updated when available?
L118 reference figure 6 here? It takes a while before the reader realises which figure they are meant to be looking at to support this paragraph. It would be helpful to add references to the relevant figure panel throughout this paragraph to help your readers. E.g. the final sentence, L129,
Figure 3. This is a great figure! Very ingenious. There’s a lot of information in these. I found the order of the 4 panels confusing – would it be easier to follow if the 4 panels progressed W-E or E-W? I wondered whether you had plotted the depth of the Tmax in the same way? (not necessarily asking for it to be included in the paper, just curious what it might show – it’s not quite the same thing as figure 5).
L125 I’m being pernickety, but I prefer “decreases” to “drops”, here and elsewhere (e.g. l108)
Caption to Figure 5. Typo here? The color code is surely the year?
L136 I think it would be helpful to add some further explanation of why you consider the green line, 24hr, to be tidal EKE.
L141 I think you should reference the figure showing this result, not the figure showing the locations.
L141 I would not use the word “now”. We don’t know what happened since February 2021, correct? It might be cold again? And it’s ambiguous when “now” is.
Figure 6. What is the red/pink solid line in panels c and d?
Figure 6. Caption says 12 hours to 2 days but figure legend says 14 hours to 2 days?
Figure 6. I think you need more explanation in caption, and also in the text, of the band pass filters you chose. The caption refers to B12, B24 and B35 but these are not defined?
Figure 7. Is this correct? These temperatures seem excessively cold, especially for WDW? They are well below freezing? Check y axis labelling?
L161 We usually say “back of the envelope”.
L161 suggest (plural estimates)
L162 Clarify, needed for what?
L168 I think you mean Weddell Sea Deep Water?
L173 The Foldvik reference needs brackets, also l209 and l217
L186 the references to the figures need Figure.
L238 Brackets need moving.
The paper ends quite abruptly, and I think it would benefit from a bit more discussion of the importance of the results, why they matter (for whom?), and what unanswered questions the work raises?
The Data availability section doesn’t mention float profiles?
Citation: https://doi.org/10.5194/egusphere-2022-1477-RC1 -
AC1: 'Reply on RC1', Elin Darelius, 28 Mar 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2022-1477/egusphere-2022-1477-AC1-supplement.pdf
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AC1: 'Reply on RC1', Elin Darelius, 28 Mar 2023
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RC2: 'Comment on egusphere-2022-1477', Anonymous Referee #2, 24 Feb 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2022-1477/egusphere-2022-1477-RC2-supplement.pdf
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AC2: 'Reply on RC2', Elin Darelius, 28 Mar 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2022-1477/egusphere-2022-1477-AC2-supplement.pdf
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AC2: 'Reply on RC2', Elin Darelius, 28 Mar 2023
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2022-1477', Karen J. Heywood, 12 Feb 2023
I enjoyed reading this paper. It is well written, clearly presented and interesting, with some ingenious analyses. The figures are very good. A particular strength is the analysis of an excellent long-term climatology that has been carefully assembled of ship, seal and float profiles in a region where there have been relatively few studies. It also presents unusually long time series from moorings near the Filchner Ronne Ice Shelf and on the continental shelf and slope. The paper discusses temporal variability, and in particular, possible causes and implications of an occurrence of surprisingly warm WDW in 2021. I found the estimates of the possible impact on AABW very interesting.
I am happy to recommend acceptance of the paper subject to consideration of some minor suggestions that I list below.
The abstract is nice, but it doesn’t really do justice to the conclusions you came to about the importance of the observed warming, for example for eventual AABW properties. It would be good to include these implications in the abstract.
L17 I wouldn’t say that the Amundsen Sea has a narrow continental shelf – it is hundreds of km from the shelf break to the vulnerable glaciers such as Pine Island and Thwaites.
L23 include a reference to moderate melt rates for FRIS?
L27 typo – you mean tenths not tens of a degree, I think.
L41 I had to read the bit after the Nicholls reference several times, as it’s difficult to make out with the commas and references breaking it up. Try to rephrase to make it easier for readers?
L54 I was curious what the source was of the remaining profiles out of the >1000 that are not ship or seals! Later on it’s clear that these are profiling floats – I would state that here. Also I recommend giving a reference to MEOP to give due credit to those assembling MEOP data – information about how to cite the data is here https://www.meop.net/database/how-to-cite.html.
Probably there is a similar reference to duly acknowledge the efforts of those assembling the Argo float data set? Both these data sources should be cited in the text as well as incldued in the data section at the end.
L64 what is OTE? Expand?
Caption to Figure 2. I get that the mentions of 1515 m depth and the 1300-1700m depth range are referring to the sea bed depth, but maybe that needs to be spelt out more clearly?
L106 and L108 Are these references to the same paper? In review? 2023? Reference list says in prep?
L116 The in review reference should be updated when available?
L118 reference figure 6 here? It takes a while before the reader realises which figure they are meant to be looking at to support this paragraph. It would be helpful to add references to the relevant figure panel throughout this paragraph to help your readers. E.g. the final sentence, L129,
Figure 3. This is a great figure! Very ingenious. There’s a lot of information in these. I found the order of the 4 panels confusing – would it be easier to follow if the 4 panels progressed W-E or E-W? I wondered whether you had plotted the depth of the Tmax in the same way? (not necessarily asking for it to be included in the paper, just curious what it might show – it’s not quite the same thing as figure 5).
L125 I’m being pernickety, but I prefer “decreases” to “drops”, here and elsewhere (e.g. l108)
Caption to Figure 5. Typo here? The color code is surely the year?
L136 I think it would be helpful to add some further explanation of why you consider the green line, 24hr, to be tidal EKE.
L141 I think you should reference the figure showing this result, not the figure showing the locations.
L141 I would not use the word “now”. We don’t know what happened since February 2021, correct? It might be cold again? And it’s ambiguous when “now” is.
Figure 6. What is the red/pink solid line in panels c and d?
Figure 6. Caption says 12 hours to 2 days but figure legend says 14 hours to 2 days?
Figure 6. I think you need more explanation in caption, and also in the text, of the band pass filters you chose. The caption refers to B12, B24 and B35 but these are not defined?
Figure 7. Is this correct? These temperatures seem excessively cold, especially for WDW? They are well below freezing? Check y axis labelling?
L161 We usually say “back of the envelope”.
L161 suggest (plural estimates)
L162 Clarify, needed for what?
L168 I think you mean Weddell Sea Deep Water?
L173 The Foldvik reference needs brackets, also l209 and l217
L186 the references to the figures need Figure.
L238 Brackets need moving.
The paper ends quite abruptly, and I think it would benefit from a bit more discussion of the importance of the results, why they matter (for whom?), and what unanswered questions the work raises?
The Data availability section doesn’t mention float profiles?
Citation: https://doi.org/10.5194/egusphere-2022-1477-RC1 -
AC1: 'Reply on RC1', Elin Darelius, 28 Mar 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2022-1477/egusphere-2022-1477-AC1-supplement.pdf
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AC1: 'Reply on RC1', Elin Darelius, 28 Mar 2023
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RC2: 'Comment on egusphere-2022-1477', Anonymous Referee #2, 24 Feb 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2022-1477/egusphere-2022-1477-RC2-supplement.pdf
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AC2: 'Reply on RC2', Elin Darelius, 28 Mar 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2022-1477/egusphere-2022-1477-AC2-supplement.pdf
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AC2: 'Reply on RC2', Elin Darelius, 28 Mar 2023
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Vår Dundas
Markus Janout
Sandra Tippenhauer
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
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