Seasonal cycle and long-term trend of solar energy fluxes through Arctic sea ice

Arndt, S.; Nicolaus, M.

doi:https://doi.org/10.5194/tc-8-2219-2014

Articles | Volume 8, issue 6

https://doi.org/10.5194/tc-8-2219-2014

© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/tc-8-2219-2014

© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 8, issue 6

Research article

|

28 Nov 2014

Research article |

| 28 Nov 2014

Seasonal cycle and long-term trend of solar energy fluxes through Arctic sea ice

S. Arndt and M. Nicolaus

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Final revised paper (published on 28 Nov 2014)
Preprint (discussion started on 05 Jun 2014)

Interactive discussion

Status: closed

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

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- Supplement

RC C1053: 'Review of tc-2014-74', Anonymous Referee #1, 01 Jul 2014
- AC C1738: 'Review of “Seasonal cycle of solar energy fluxes through Arctic sea ice” by S. Arndt and M. Nicolaus', Stefanie Arndt, 05 Sep 2014
RC C1512: 'Review of “Seasonal cycle of solar energy ﬂuxes through Arctic sea ice” by S. Arndt and M. Nicolaus', Anonymous Referee #2, 12 Aug 2014
- AC C1739: 'Review of “Seasonal cycle of solar energy fluxes through Arctic sea ice” by S. Arndt and M. Nicolaus', Stefanie Arndt, 05 Sep 2014

Peer-review completion

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

AR by Stefanie Arndt on behalf of the Authors (05 Sep 2014) Author's response Manuscript

ED: Referee Nomination & Report Request started (08 Sep 2014) by Ron Lindsay

RR by Anonymous Referee #2 (10 Sep 2014)

RR by Anonymous Referee #1 (23 Sep 2014)

Suggestions for revision or reasons for rejection

The authors have clearly made substantial improvements to this manuscript. It is my opinion that this study should be published. There is no question that there are limitations to the study, but I think the authors have adequately described them. This being said, there are still numerous places in the manuscript where the language is not clear and I find the meaning questionable.

p2. line 26: “Arctic sea ice has not only decreased…”. The amount, or the extent, or the thickness has decreased, not the ice. “The amount of Arctic sea ice has not only decreased….”

2.30: ‘sufficiently well’? what does this mean? By whose standard is the quantification sufficient? Maybe just delete these two words.

2.32: maximum monthly mean solar heat flux where? Below the ice?

2.33: “…accounting for an equivalent ice melt of approximately 30 cm per month.” well, not really “accounting” because there is no attempt here to relate this estimate to an observed ice ablation. I think it would be better to say ‘yielding possible ice melt’ or ‘potential ice melt’?

2.34: “…96% of total annual solar heat input occurs from May to August…” If this is just heat input through ice and does not include heat into the open ocean then this statement is wrong as it is currently written.

2.37: “…increase of light transmission of 1.5% / year”? This is unclear. Which is meant, “increased transmitted light” or “increased transmission of light”? It matters.

2.42-44: “Continuing the observed transition from Arctic multi- to first year sea ice could increase light transmittance by another 18%.” This is an open ended statement, so it’s not clear by when the 18% could be achieved.

3.59: change “various studies showed” to “various studies have shown…”

3.66: “was possible” to “has been possible”

3.69: “spatial variability” and “seasonal changes” don’t really belong in this list of specific physical attributes. Spatial variability of what? Seasonal changes of what?

6.120-121: It’s fine to exclude open water areas since the authors have now made it clear that they are doing so and why, but the work of Perovich (2007a) should be referenced here.

7.168: extra “data”

11.269 – 12.276: I don’t understand this paragraph. What exactly is meant by “inverse behavior”? Is it meant “…increase in transmittance of growing sea ice…”? Why is “aggregate scale” important? Furthermore, I don’t see at all how it relates to Figure 2, where transmittance of 0.4 is not depicted. Also, I don’t see an exponential change between EMO and the last day of melting in this figure. This paragraph needs to be rewritten.

12.279: Perovich et al. (2002) also commented about duration of snow melt, so it would be worthwhile to consider their estimate as well.

12.286: The language here implies that the minimum ice concentration is always during phase IV? Ice concentration is tightly tied to dynamics; I don’t understand why it should be tied to thermodynamics.

12.287: that undergo comparably small changes?

12.288 – 292: Descriptions appear ambiguous. Does “pond covered ice” mean just the pond or the ponded ice cover (as was defined earlier?). Then why do these number get weighted by melt pond fractions?

15.363: why the word “strong”? Do the authors mean “rapid” snow melt instead?

16.380-383: Fig 4a shows annual average heat input, yes? That’s not clearly stated in the figure description here. Also m or cm?

16.384-385: “The mean total solar heat input per grid cell in the area of the mean sea ice extent was 46 MJm-2.” What does this mean?? Per grid cell, but also per m^2? And what does “area of mean sea ice extent” mean?

16:385-387: “The maximum QT(x,y) occurs at the edge of the marginal ice zone in the Canadian Arctic Archipelago (up to 110 MJm-2 386 /130 cm melt per year) and the East Siberian Sea and Chukchi Sea (up to 80 MJm-2 /94 cm melt per year).” So is this describing what the authors call “ice edge effects”? What is the physical explanation of this?

16.388: What does “excluding ice edge effects” mean?

16.391: Again, I don’t understand what the “sea ice edge effects” are?

17.403-404: where is this increasing variability be seen? Is it just being eyeballed off the figure? It should be quantified.

18.443-444: “Speculation of even greater pond coverage might even increase the trends.” This doesn’t make sense to me. If the pond fraction was even larger than assumed prior to 2000, then seems this would decrease the trend. The third sentence in this paragraph doesn’t follow at all.

19.448-462: I am really having a difficult time understanding this paragraph. In particular, what is the “ice concentration effect”? Where does “annual trend of +-1.1% a-1” come from? It does not follow why this comparison “emphasizes the dominance of the albedo feedback mechanism”. This paragraph needs to be rewritten.

24.587: adding up to > 100%? Figure only goes up to 50%.

26.622-623: How is 63% calculated from 1.5%/year for 33 years?

26.628-630: How is this known? Heat fluxes through the ice haven’t been compared here with heat fluxes through open ocean / retreating ice concentration!

26:632: what is meant by “access heat”?

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RR by Anonymous Referee #3 (30 Sep 2014)

Suggestions for revision or reasons for rejection

Review of Arndt and Nicolaus, 2014 TCD
Seasonal cycle and long term trend of solar energy fluxes through sea
ice.

2nd round review, TCD, revised after 'major revisions' 14 June 2014.
File: tc-2014-74-manuscript-version3.pdf

Major comments:

The science contained in this manuscript is publishable, and should be
published. However, the manuscript in its present form is very
difficult to read, and suffers from both language and organizational
shortcomings. I also raise some outstanding questions regarding the
science. In my opinion, the article still needs quite a bit of work
before publication, and so I suggest major revisions.

1. Both of the previous reviewers suggested that the English is
awkward in more than one place. This remains a problem in this
version of the manuscript. The authors really need to have a native
English speaker correct grammatical and punctuation mistakes, as well
as suggest improvements for clarity. The authors use many
introductory phrases and transition words inappropriately and the
manuscript as a result is difficult to read for a native speaker who
can interpret what is written. It will be even more confusing for
non-native English speakers. Much of it can be simplified and made
more clear.

2. Open water is not specifically treated here. However, the use of
sea ice concentration implies an implicit treatment of fractional open
water coverage. Presumably in cases where the sea ice concentration
is much less than 100%, the transmittance of light through leads will
also dominate the light conditions, as well as the energy absorbed in
the water column. It seems there should be a discussion on this point
- both in terms of the transmission levels as well as the absorbed
energy and therefore melt potential. This presumably would also swamp
the signal of changes through the ice itself in low sea ice
concentrations. Are trends in in transmittance useful (or even
appropriate) in areas where the ice has retreated for at least some
months of the year? A comparison (as in Nicolaus 2012/2013) of the
solar absorption in open water may be useful.

3. The ERA-Interim data is used for the incoming surface solar
irradiance. How do changes in incoming solar affect the budget and/or
trends? The authors could do a direct assessment on the incoming solar
field (or there may be literature on it already), or they could
evaluate the results against a 'clear-sky' solar irradiance. The
latter would most clearly get at changes induced by the ice itself, as
compared to changes mitigated by changes in incoming solar.

4. I also agree with the previous reviewer's comment who suggests a
test of the parameterization against the melt-pond fractions in Flocco
2010 or Flocco 2012. Though I understand the author's desire to keep
this an empirical result based on observed quantities rather than
modeled, I would argue that the use of reanalysis data for the primary
input dataset is already a model result, and the parameterization is
also missing the ice thickness and/or snow depth quantities that might
make the whole exercise more straightforward. A comparison to the
modeled pond result which may have some consistency between ice
thickness, snow depths, and pond fractions might strengthen the point
of the authors.

5. L88-102 The description of the contents of the paper still does not
capture what I see as the main story. . I would suggest that the
authors make a simple summary here of what they accomplish in this
paper. Though a matter of semantics, it is not really a 'new method;'
rather it is an estimate of an annual budget for shortwave radiative
transfer through sea ice and into the water column, based on on
existing (and incomplete) data sets.

The 'new' part of the parameterization involves the melt-pond fraction
only, correct? Or do the authors include the classification of the ice
surface conditions? I'd suggest that it is one and the same, and
might emphasize not that it's 'new' but is an extension of Nicolaus
2012/2013 as a first attempt that to quantify changes through the
annual cycle.

One suggestion for this paragraph might be:

"In order to improve the understanding of the ongoing change in sea
ice conditions and 89 the associated impact on the partitioning of
solar energy, we provide an estimate of the monthly shortwave
radiative transfer through sea ice for the entire Arctic for the years
1979 to 2011. We use a definition of 6 types of sea ice over the
annual cycle, define 6 distinct time periods of insolation conditions,
and include the temporal and spatial variability of melt ponds to
extend and generalize the up-‐scaling method of Nicolaus et
al. (2012) and (2013)."

The rest of the details in the paragraph made it seem like the authors
were accomplishing a list of 4-6 different things. Again it can be
kept much simpler and clearer.

Organization:

Methods: I suggest introducing the parameterization first (Sec 2.2),
followed by the datasets. I also suggest introducing eq 2 first, and
introduce eq 1 as the exception due to the lack of data for melt ponds.
Its not clear how the transmittances in fig 2 for melting MYI and
melting FYI relate to the terms in Eq 2. Its not clear why the
authors mention open water in Fig 2 caption, when it is not included
in the equations 1 or 2 (though it probably should be).

I suggest that Sec 4 not be labeled its own section, and instead
become subsections for section 3. 4.2 should not be labeled
'Validation', since it is not. Perhaps 'Comparison with direct
observations'. Any further discussion can be wrapped into the last
section.

Specific comments (not exhaustive)

Abstract: L42 - The annual budget of what increases by 20%? One of
the reviewers also raised this point. I assume you mean the annual
transmittance of solar radiation to the water column increases by
20% given a two week increase in melt season.

Fig 1. The text discussion of the 6 ice types is at odds with the
figure diagram with the 6 labeled seasons. Please clarify in
the text and figure.

Fig 2. What happens to the MY transmittances after season IV? What
is the maximum transmittances that the curves approach? Including them
by a discontinuous scale might be a way to represent it. Why does the
MYI split into a 'melting MYI' and a constant MYI in season IV?
(Same for FYI?) It is not explained what the significance of this is.

Trends: Given the assumption of constant melt-pond coverage for prior
to 2000, it is difficult to see how trends can be meaningful for
1979-2011. If the authors want to include these trends, it is
suggested that they be reported also for the period 2000-2011. It is
not clear why pre-2000 values are set to 2011 mean values, instead of
to 2000 mean values.

The problem with comparison to the Tara drift measurements for August
(L 481-484) is not clear - is it only in the water column? Or within
the ice? Is the depth of the sensor too far from the ice interface?

---- end of review

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ED: Reconsider after major revisions (30 Sep 2014) by Ron Lindsay

AR by Stefanie Arndt on behalf of the Authors (15 Oct 2014) Author's response Manuscript

ED: Referee Nomination & Report Request started (18 Oct 2014) by Ron Lindsay

RR by Anonymous Referee #2 (27 Oct 2014)

RR by Anonymous Referee #1 (03 Nov 2014)

ED: Publish subject to minor revisions (Editor review) (04 Nov 2014) by Ron Lindsay

AR by Stefanie Arndt on behalf of the Authors (04 Nov 2014) Author's response Manuscript

ED: Publish subject to technical corrections (05 Nov 2014) by Ron Lindsay

AR by Stefanie Arndt on behalf of the Authors (05 Nov 2014) Manuscript