Baffin Bay sea ice inflow and outflow: 1978–1979 to 2016–2017

Bi, Haibo; Zhang, Zehua; Wang, Yunhe; Xu, Xiuli; Liang, Yu; Huang, Jue; Liu, Yilin; Fu, Min

doi:https://doi.org/10.5194/tc-13-1025-2019

Articles | Volume 13, issue 3

https://doi.org/10.5194/tc-13-1025-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/tc-13-1025-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 13, issue 3

Research article

|

29 Mar 2019

Research article |

| 29 Mar 2019

Baffin Bay sea ice inflow and outflow: 1978–1979 to 2016–2017

Haibo Bi, Zehua Zhang, Yunhe Wang, Xiuli Xu, Yu Liang, Jue Huang, Yilin Liu, and Min Fu

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Final revised paper (published on 29 Mar 2019)
Supplement to the final revised paper
Preprint (discussion started on 23 Jul 2018)

Interactive discussion

Status: closed

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

- Printer-friendly version

- Supplement

RC1: 'Haibo et la. Baffin Bay sea ice flux paper review', Anonymous Referee #1, 14 Aug 2018
- AC1: 'Response to comments of reviewers', Haibo Bi, 30 Nov 2018
RC2: 'Satellite-observed sea ice area flux through Baffin Bay: 1988-2015. The Cryosphere Discuss. https://doi.org/10.5194/tc-2018-136 Haibo Bi et al.', Anonymous Referee #2, 28 Aug 2018
- AC2: 'Response to reviewer 2#', Haibo Bi, 30 Nov 2018
RC3: 'Review of "Satellite-observed sea ice area flux through Baffin Bay:1988-2015" by Haibo Bi et al.', Anonymous Referee #3, 31 Aug 2018
- AC3: 'Response to Reviewer 3', Haibo Bi, 30 Nov 2018

Peer-review completion

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

AR by Haibo Bi on behalf of the Authors (03 Dec 2018)

ED: Referee Nomination & Report Request started (17 Dec 2018) by John Yackel

RR by Anonymous Referee #1 (20 Dec 2018)

RR by Anonymous Referee #3 (08 Jan 2019)

Suggestions for revision or reasons for rejection

2nd Review

Baffin Bay sea ice inflow and outflow:1978/1979-2016/2017

General Comments:

The paper has changed significantly and now focusses on sea ice area flux through Baffin Bay, using three gates (different ones compared to the first version). The authors also expand the time series, now including the full time span of the NSIDC ice motion data set starting in 1978. The comparison with the Fram Strait flux has been discarded.
Unfortunately, the revision does include a track of the changes in the new version of the paper. But from what I found, it seems that major parts of the paper have been rewritten and restructured. This is acknowledged and I find the paper improved now, following a certain thread. Also the quality and compilation of figures has improved.
The major objective of the paper is to derive long term trends and variations in sea ice flux through Baffin Bay. Former studies (Cuny et al., 2005, Curry et al., 2014, Kwok, 2007) have presented sea ice flux retrievals in the Baffin Bay already, but only on shorter time scales. Still, my major objections are regarding the soundness of the study:

1. Evaluation of the sea ice motion: The authors write: “To assess the NSIDC data, a reference product of sea ice motion, which is visually retrieved from high-resolution (~100 m) Envisat wide-swath (~450 km) observations, is employed”. I wonder what is meant by “visually”? It should be based on a robust retrieval algorithm!? In any case, you should describe how you have retrieved the reference ice drift from the Envisat data in much more detail. Moreover, it is not well described how the comparison is performed.

2. For the uncertainty of the NSIDC ice motion, you use the standard deviation of difference (3.11 km/day) between the NSIDC and Envisat-derived ice drift. I don’t think that this accounts for the real uncertainty. There is a nice paper by Sumata et al. (2015), which provides an empirical error function for different sea ice drift products, including the NSIDC retrieval. It also shows that the uncertainty increases with higher drift speeds, i.e. underestimation of high drift speeds.

3. The study heavily relies on the NSIDC data set and assumes that this data set is consistent over the entire period from 2978-2018, despite the fact that many different sensors have been used for different periods to construct this time series. In order to calculate trends, the consistency should be validated and profound uncertainty estimates have to be provided.

4. The ice growth model used in section 2.3 is very basic and simple. For example, it does not handle variations in the snow cover?! Moreover, the derived decrease in thickness is then used to explain trends in the ice motion due to wind (see Eq 2). But the air-ice drag coefficient is not considered here neither, although it is an important parameter, resulting from the surface and bottom roughness of the sea ice. This approach seems to be very vague.

Therefore, I think very major revisions are necessary again and I regret to suggest to reject this paper.

Detailed comments:

P2L5: “a northward flowing West Greenland Current (WGC) along the Greenland coast 5 carries warm and salty water from the North Atlantic” … Figure 1 says it is “cold”?

P4L5-16: How is the reference ice drift derived?

Figure2: Are you comparing different periods? It looks like you compare Envisat ice drift from Feb 19-22 with NSIDC ice drift from Feb 4-7. You have to describe in much more detail how the comparison between NSIDC and Envisat ice drift is performed and how Envisat ice drift is derived.

Figure 4: Fast ice edges from the different periods are hard to distinguish. May be zoom in the different regions.

Figure 5: Error bars are missing.

Section 2.2.2: The used gates in other studies seem to be at different locations. How does this affect the comparison?

Figure 10: How do you explain that the mean sea ice area flux in the 1978-1987 period is so low compared to the later periods? In any case, this needs to be investigated in more detail (see my concern about the consistency of the NSIDC data set).

Figure 12: unit - How do you derive “km” from the divergence of a velocity field? Should it not be 1/s (or 1/d) ?

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ED: Reconsider after major revisions (08 Jan 2019) by John Yackel

AR by Haibo Bi on behalf of the Authors (19 Feb 2019)

ED: Publish subject to technical corrections (26 Feb 2019) by John Yackel

AR by Haibo Bi on behalf of the Authors (06 Mar 2019) Manuscript

Short summary

Baffin Bay serves as a huge reservoir of sea ice which provides solid freshwater sources for the seas downstream. Based on satellite observations, significant increasing trends are found for the annual sea ice area flux through the three gates. These trends are chiefly related to the increasing ice motion which is associated with thinner ice owing to the warmer climate (i.e., higher surface air temperature and shortened freezing period) and increased air and water drag coefficients.