Continuous monitoring of surface water vapour isotopic compositions at Neumayer Station III, East Antarctica

Bagheri Dastgerdi, Saeid; Behrens, Melanie; Bonne, Jean-Louis; Hörhold, Maria; Lohmann, Gerrit; Schlosser, Elisabeth; Werner, Martin

doi:https://doi.org/10.5194/tc-15-4745-2021

Articles | Volume 15, issue 10

https://doi.org/10.5194/tc-15-4745-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/tc-15-4745-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 15, issue 10

Research article

|

11 Oct 2021

Research article |

| 11 Oct 2021

Continuous monitoring of surface water vapour isotopic compositions at Neumayer Station III, East Antarctica

Saeid Bagheri Dastgerdi, Melanie Behrens, Jean-Louis Bonne, Maria Hörhold, Gerrit Lohmann, Elisabeth Schlosser, and Martin Werner

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Final revised paper (published on 11 Oct 2021)
Preprint (discussion started on 27 Oct 2020)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Review 1', Anonymous Referee #1, 17 Nov 2020
- AC1: 'Reply on RC1', Saeid Bagheri Dastgerdi, 12 Mar 2021
RC2: 'Great data, mediocre interpretation.', Anonymous Referee #2, 21 Dec 2020
- AC2: 'Reply on RC2', Saeid Bagheri Dastgerdi, 12 Mar 2021
RC3: 'Review', Anonymous Referee #3, 27 Jan 2021
- AC3: 'Reply on RC3', Saeid Bagheri Dastgerdi, 12 Mar 2021
EC1: 'Comment on tc-2020-302', Jean-Louis Tison, 28 Jan 2021
- AC4: 'Reply on EC1', Saeid Bagheri Dastgerdi, 12 Mar 2021

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Reconsider after major revisions (further review by editor and referees) (19 Mar 2021) by Jean-Louis Tison

AR by Saeid Bagheri Dastgerdi on behalf of the Authors (21 Apr 2021) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (04 May 2021) by Jean-Louis Tison

RR by Anonymous Referee #3 (11 May 2021)

Suggestions for revision or reasons for rejection

l. 87: “The station is situated on the 200-meter thick Ekström ice shelf” This is the local ice thickness, ice shelf thickness typically increases strongly towards the grounding line.

l. 98: “These low-pressure systems move toward west around Antarctica” Generally, low-pressure systems move eastwards with the westerly circulation around Antarctica.

l. 113: “In this study, temperature, relative and specific humidity…” Temperature and relative humidity are measured directly, after which specific humidity is then calculated, also using pressure.

l. 228: “Daily relative humidity fluctuates between 59.95 % and 96.71 % with a mean value of 80.42 %.” Suggest changing to “Daily relative humidity fluctuates between 60 % and 97 % with a mean value of 80 %.”

l. 232: “-15.81◦C and -15.65” -> “-15.8◦C and -15.7”

l. 258-260: Use one decimal for temperature.

l. 268: “In winter, clouds can be much warmer than the surface, which leads to a strong temperature inversion. However, changes in wind speed and direction might change the cloud cover and thereby weaken or destroy the inversion layer, in short time.”

Suggest to change to:

“Especially in winter, clouds warm the surface, limiting or destroying a temperature inversion that may have been present under clear skies. Similarly, increases in wind speed may also weaken or destroy the inversion layer, in a short time.”

l. 272 and further: “As sea ice can strongly limit the heat flux between a relatively warm ocean and the atmosphere, sea ice coverage variations close to Antarctica’s coastal stations can primarily affect the near-surface temperature at the stations (Turner et al., 2020). Decreasing sea ice variability close to the Neumayer Station in summer compared to other seasons, which is true for most other coastal stations in Antarctica, may also lower the temperature variability. Another reason for the reduced temperature variations in summer can be a stronger heat loss, which prevents temperatures above zero. At Neumayer Station, the largest sources of heat loss in summer are sublimation and snow melting (Jakobs et al., 2019). The sublimation is primarily temperature-controlled and is only significant at Neumayer station in summer. About 19% of the annual snowfall at this location is removed by sublimation (van den Broeke et al., 2010). The second source of heat loss at the station is snow melting. In summertime, when the air temperature can rise above 0 ◦ C, the surface snow will reach its melting point and start to melt. For the melting process, the incoming radiative energy is partly used for latent heat uptake, keeping the near-surface temperature close to the melting point.”

Suggest to change to:

In summer, interdiurnal temperature variations are strongly reduced. The primary reason is that absorption of solar radiation prevents the formation of near-surface temperature inversions, limiting the above-described processes. As sea ice can strongly limit the heat flux between a relatively warm ocean and the atmosphere, sea ice coverage variations close to Antarctica’s coastal stations can primarily affect the near-surface temperature at the stations (Turner et al., 2020). Decreasing sea ice variability close to the Neumayer Station in summer compared to other seasons decreases spatial regional temperature gradients, which is true for most other coastal stations in Antarctica, may also lower the temperature variability. Finally, in summertime, the air temperature sometimes can rise above 0 ◦ C, and the surface snow will reach its melting point and start to melt. For the melting process, the incoming radiative energy is partly used for latent heat uptake, keeping the near-surface temperature close to the melting point.”

l. 310: “Moisture uptake coming to Neumayer Station depends on different factors such as sea ice extent, the Southern Hemisphere semi-annual oscillation (SAO), and absolute temperature. As Fig. 5 shows, the sea ice prevents evaporation from the ocean. In the areas with ice coverage more than 90 %, the moisture uptake is minor. The SAO is the main phenomenon that affects surface pressure changes at the middle and high latitudes of the Southern Hemisphere (Schwerdtfeger, 1967). It means the twice-yearly contraction and compression of the pressure belt surrounding Antarctica as a result of the different heat capacities of the Antarctic continent and the ocean. The SAO leads to a clear half-yearly pressure wave in surface pressure at high latitudes and modifies the atmospheric circulation and temperature cycles (Van Den Broeke, 1998).”

Suggest to change to

“Moisture uptake and subsequent transport to Neumayer Station depend on different factors such as sea ice extent and the track of cyclones. As Fig. 5 shows, the sea ice prevents evaporation from the ocean. In the areas with ice coverage of more than 90 %, the moisture uptake is minor. The SAO is the main seasonal phenomenon that affects surface pressure changes at the middle and high latitudes of the Southern Hemisphere (Schwerdtfeger, 1967). It represents the twice-yearly contraction/expansion of the low-pressure belt surrounding Antarctica as a result of the peaking/dipping latitudinal gradient in solar radiation. This leads to a clear half-yearly cycle in meridional fetch and associated heat and moisture transport which strongly modifies the temperature cycles in coastal Antarctica (Van Den Broeke, 1998).”

l. 326: 5.67 -> 5.7

l. 355 -> 365: for the meteorological variables, use a single decimal. Do this throughout.

l. 367: “A very high correlation coefficient between δ 18O and 2-meter temperature (r = 0.98) and 10-meter temperature (r = 0.99) suggests the temperature changes as the main driver of water vapour δ 18O diurnal variations” The fact that both variables show a daily cycle will result in high correlation but does not prove causation. Could be solar radiation, sublimation, boundary layer depth….this also applies to similar statements elsewhere in the paper.

l. 398: I could be wrong, but it appears that Fig. 10 is referenced before Fig. 9.

l. 402: pattern -> patterns

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RR by Anonymous Referee #2 (14 May 2021)

ED: Publish subject to minor revisions (review by editor) (28 May 2021) by Jean-Louis Tison

AR by Saeid Bagheri Dastgerdi on behalf of the Authors (11 Aug 2021) Author's response Author's tracked changes Manuscript

ED: Publish subject to minor revisions (review by editor) (27 Aug 2021) by Jean-Louis Tison

AR by Saeid Bagheri Dastgerdi on behalf of the Authors (06 Sep 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (07 Sep 2021) by Jean-Louis Tison

AR by Saeid Bagheri Dastgerdi on behalf of the Authors (13 Sep 2021) Manuscript

Short summary

In this study, for the first time, water vapour isotope measurements in Antarctica for all seasons of a year are performed. Local temperature is identified as the main driver of δ¹⁸O and δD variability. A similar slope of the temperature–δ¹⁸O relationship in vapour and surface snow points to the water vapour isotope content as a potential key driver. This dataset can be used as a new dataset to evaluate the capability of isotope-enhanced climate models.