Dear Dr Istomina,

thank you for your thorough revision of your manuscript and addressing the reviewers’ comments in detail.

Both reviewers find the separation of the methods into a manuscript separate from the results has greatly improved the paper, making both parts suitable for publication. Reviewer 1 has some additional, minor comments that would need to be addressed in a final set of revisions.

In my own review, I also noted a few items that still need to be corrected or revised, details are provided below.

With best regards,

Hajo Eicken

Editor, The Cryosphere/Discussions


Paper 1

General comment

One issue that needs to be resolved and discussed in the text concerns your definition of melt ponds in the late season and how this corresponds to relevant satellite data. In figure 16 you indicate that the estimated pond fraction is 0.5. However, this is based on the assumption that you can identify former ponds that are now frozen over by their former outlines. When does such a pond turn from “pond” to “sea ice”? Early in the season, temporary ice cover on ponds may be discounted since this typically melts back within a day or so. However, late in the season (i.e. September) it makes more sense to clearly draw the line between ponds and a solid ice surface that was formerly a pond.
This is more than semantics. If you look at your figure 3, the retrieved pond fraction remains high (>0.1) throughout September and into early October. Are you implying that MERIS is actually detecting former ponds? Depending on what the geographic coverage of Fig. 3 is, I don’t quite follow how you can have a remaining pond fraction of 0.1 or more in late September unless this includes frozen, former ponds. The way the curves oscillate around a stable (?) mean in September suggests that this is some type of bias in the data rather than a real feature. This is quite important because it may also apply to data in May (if a similar bias exists for unponded ice early in the season).
Please be sure to discuss the implications and confirm the definition used for pond observations & validation (re Fig 16).


Specific comments

p. 1; l. 1: remove “The” from title to read “Melt pond fraction…”
p. 1, l 22: change to “consequences for the heat” (here and below the suggested edits will be listed in quotation marks”
p. 1, l 23: “from MEdium Resolution”
p. 2, l .6: Please write out the acronym ASPECT and be sure to address the comment made for p. 15, l. 12)
p. 2, l. 16: Here and throughout the manuscripts replace “melting season” and “melting temperatures” with “melt season” and “melt temperatures”
p 2, l 26: “, e.g. Rösel et al. (2012) or Tschudi et al. (2008)” - i.e., only place the year in parentheses here and throughout the manuscript when referring to specific studies in the text.
p 3, l. 21: “Zege et al. (2015)” - see previous comment
p. 7, l. 28/29: “clouds have lower albedo”
p 11, l 5: Abbreviation for fast ice (FI) needs to be introduced here, not further down in the text.
p 13, l 18: What is “thrashed ice” ? are you referring to brash ice?
p 14, l 8: Again, “thrashed ice” needs to be corrected, there is no such term in the glaciological nomenclature (at least not based on WMO nomenclature).
p 15, l 12: Referring to ASPECT protocol raises several issues. First, ASPECT needs to be written out, but more importantly it needs to be confirmed that ASPECT protocol was in fact used. My understanding is that on recent Polarstern cruises the IceWatch protocol has been followed (http://www.iarc.uaf.edu/en/icewatch) which differs in important details, in particular with respect to melt pond fractions and typology from ASPECT. Maybe this was not yet the case in 2011, but needs to be confirmed for the two cruises that you reference. A general statement such as “most often performed according to ASPECT protocol is not sufficient. For HOTRAX my understanding is that an early version of the IceWatch protocol was used. Also, you should provide a reference, either in a publication or a website to the specific protocol that was employed.
p 15, l 24: “available”
p 19, l 22: delete “, .”
p 19, l 25: “Richter-Menge, J.A.”
p 20, l. 6: De Abreu, R.A.”
p 20, l 19: Use consistent abbreviation for Edition (see l 1 on same page); preferably write it out fully.
p 20, l 21/22: “Klyukov, D.A.”
p 20, l 31: The Lehmann reference is missing bibliographic information. Is this a report, a thesis or something else? Also please be sure to correct the orthography “Messungen für Nordostgrönland”
p 21, l 10: “University Press,”
p 21, l 25: delete extra “,”
p 21, l 31: both initials “A” need to be upper case
p 25: In the result column of Table 3, what is the reference to “Not a number” (NaN) meant to indicate? Are you saying that the total albedo could not be retrieved? If so, N/A (not available) would be the term to use.
p 26, l 4 “shown in red” instead of “marked with the red color”
p 29, l 2: deleted “from”
p 29: In the figure caption for Figure 3 please indicate what region this time series represents. Are these all swaths for a particular near-synoptic acquisition?
p 31: The standard deviation shown by the color scale on the right looks very low; if i interpret this correctly you are seeing a standard deviation of of less than 0.005 in albedo for many of the aerial survey measurements? Please check and make sure this is correct and not a potential shift in the decimal point. How long are the transects over which this st. dev. is calculated? The text doesn’t provide any details on this as far as I can tell.
p. 35: Please provide a scale bar or a description as to the size of the scene.
p 40, l 6: “thrashed ice” - unclear what you refer to here, see comments above.


Paper 2

General comments

Given the importance of seasonal evolution of ponds in the context of your paper, it would be important to clearly separate different stages of melt in the paper. At present, it appears as if you equate the onset of visible, expansive ponding with the onset of melt, for example in Section 3.3 of the paper and other spots throughout (e.g., Figure caption for Fig. 4). As outlined in the comments for paper 1, a clear distinction between different seasonal stages of melt on FY and MY ice is important to avoid confusion or misinterpretation of satellite data. For pond evolution (which is different from the different stages of melt!), it may help to refer to the literature (such as Polashenski et al., 2012 or the paper by Eicken et al., J. Geophys. Res., 107(C10), 8046, doi:10.1029/2000JC000583, 2002 - which delineates different stages of pond evolution based on pond coverage and ice processes) to discuss findings from MERIS/MODIS data in terms of pond evolution stage. It needs to be made clear that onset of melt will occur well before any ponds can be detected in MERIS or MODIS data. Hence, some of the low pond coverages in May shown in Figure 2 may be due to bias (see discussion by Roesel et al. 2012 on this topic) rather than indications of ponding. At the same time, your findings shown in Fig. 3 for wide spread melt ponding in Week 2 of 2007 are not associated with onset of melt but represent the last phase of Stage 1 of pond evolution before the transition into Stage 2 (as outlined in Eicken et al. 2002). Please clarify in the text.

In Figure 1 you should a large area north of Barrow labeled as FY ice. Does the white circle correspond exactly to the area studied or is this merely a schematic. In 2007 much of that area shown in Fig. 1 was a mixture of multiyear and first-year ice. This is important to highlight because it may explain some of the differences observed between 2007 and 2011 and the regional contrasts in melt onset between Beaufort and eastern Chukchi Sea and the central/western Chukchi Sea.

Specific comments

p 1, l 14: “current state and trend of the climate”
p 1, l 16: “Melt Pond Detection (MPD) retrieval scheme for MEdium Resolution Imaging Spectrometer (MERIS) satellite data.”
p 1, l17: This section of the abstract is difficult to follow. While I’m not sure what exactly you are stating here, one suggestion to change (if my interpretation is correct) would be to write: “This study compares sea ice albedo and MPF to reanalysis air surface temperatures, compares MPF retrieved from MERIS to those obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS), and examines albedo and MPF trends. Weekly averages of MPF for 2007 and 2011 showed different MPF dynamics while summer sea ice minimum was similar for both years. The gridded…”
p 1, l 24ff: “a negative MPF trend in … connected to a change of the absolute MPF value at its peak, but no temporal shift, and a positive trend around the Queen … onset, with the peak MPF values unchanged.”
p 2: l. 1ff: “as opposed to the Queen Elizabeth Islands where MPF dynamics react to an earlier seasonal onset of melt.”
p 2, l10: Here and throughout ms change “melting season” to “melt season”
p 2, l 11: “of a changing Arctic due to the sensitivity”
p 2, l17ff: “can help improve understanding of the current state and trends of the energy balance”
p 2, l 18&19: Delete the sentence “One of the evidence…” it is confusingly worded, repeats a point stated earlier and is hence not needed.
p. 3, l 2: As mentioned for paper 1, if you cite a reference in the context as done here, you need to write it as “Schröder et al. (2014)”, this needs to be corrected through the manuscript, such as later on the same page where you refer to Roesel and Kaleschke.
p. 3, l 5 and l 9 and l 26: Please write out MERIS, NCEP and NSIDC in full the first time you introduce them in the main body of the text so that the acronyms are clear.
p 3, l 12: “dynamics have been”
p 4 l 4: delete extra period at end of sentence
p 4 l 10: “will still affect the gridded”
p 4 l 14: “assigned not a number value” OK, this explains NaN in the previous paper; N/A may still be better in the table in Paper 1 but you can leave the NaN reference here.
p 4 l21: The last sentence is missing a verb but I’m wondering whether it’s even necessary since the same thing is expressed in the section captions. Also, there is a problem with Section 2.1 - this is the only subsection in Section 2 and I’m not sure what exactly the case studies are. From what I can tell, you really only need one section 2 which would be titled something like: “Comparisons between surface air temperature and time series of MPF and albedo: Case studies for FYI and MYI”
p 8 l 22: “Comparison to MPF from MODIS data (Roesel et al., 2012)
p 9, l 10: “it is apparent that for June”
p 9 l 16ff: this sentence is difficult to follow, suggest reword to “The primary reason for this difference is likely the contrast in cloud screening between the two datasets, with MODIS much better suited to cloud screening over snow, resulting in differences in the fraction of unscreened clouds between both datasets.”
p 9 l26: “suggest that the bias … from possibly inaccurate assumptions about sea ice optical”
p 9, l28/29: Delete the text in parentheses (“in some locations…”), it is confusing and not necessary.
p 9 l 30: “18 June 2011”
p 9 l 31: “slight differences in”
p 10, l7: “are sensitive”
p 10 l5 and l12: The use of (1) and (2) so widely spaced apart and with a semicolon in front of (2) is confusing; please eliminate the numbers, they are not needed. Also, please delete the semicolon in front of the last sentence in the paragraph.
p 10 l 15: Garbled sentence, do you mean to say “with the NCEP surface air temperature data”?
p 10 l 21: “are the most”
p 10, l 23: “and a positive trend of 1-2% during the early melt season is found near the Queen”
p 10 l 25: “explanation for this finding is not the increase in the absolute value of the MPF, but rather the earlier melt onset … to early season data” - last part of the sentence was unclear, I’m assuming “beginning of the dataset” refers to early season data, if not then please modify.
p 11 l 19: “warm air masses”
p 11 l 26ff: “i.e. an increasing trend for MPF yields a decreasing trend of the albedo. A decreasing… around the … to dynamics of the apparent MPF weekly trends”
p 12 l 24ff: “a negative MPF trend … connected to a change … shift, a positive MPF trend around the Queen …. but with peak …”
p 12 l 29: “opposed to the Queen Elizabeth Islands … dynamics react to earlier onset of melt.”
p 16 l 4: “Greenland”
p 17: Please indicate in the figure caption that Barrow data are shown in red and MYI data shown in blue.

Dear Dr. Istomina,

Thank you for your thorough revisions of the two papers. At this point there are only a few minor technical corrections to be made that don’t require an additional review but can be completed when moving the manuscripts to the publication stage.

With best regards,

Hajo Eicken.


Minor technical corrections

Paper 1:

p. 3, l. 26: here and throughout the text remove the comma between “et al.” and the year in parentheses “(2015)”, i.e., it should read “Zege et al. (2015)”.

p. 6, l. 16: change to “are retrieved as such.”

p. 16, l.14, change to: “lead to lack of fields for detailed description of the state of melt ponds. “

p. 32, l. 8: change to “Only pixels”


Paper 2:

p. 5, l. 14: change to “and the bias in MPF and albedo”

p. 17, l. 3: change to “Schematic depiction of the case study locations”