Impact of Atmospheric Rivers on Arctic Sea Ice Variations
Abstract. Arctic sea ice has been declining rapidly in recent decades. We investigate how poleward transport of moisture and heat from lower latitudes through atmospheric rivers (ARs) influences Arctic sea ice variations. We use ERA5 hourly reanalysis data for 1981–2020 at 0.25º x 0.25º resolution to examine meteorological conditions and sea ice changes associated with ARs in the Arctic. In years 2012 and 2020, which had extremely low summer Arctic sea ice extent, we show that individual AR events associated with large cyclones initiate rapid sea ice decrease through turbulent heat fluxes, longwave radiation, and winds. We further carry out statistical analysis of meteorological conditions and sea ice variations for 1981–2020 over the entire Arctic Ocean. We find that, on weather timescales, atmospheric moisture content anticorrelates significantly with sea ice concentration tendency almost everywhere in the Arctic Ocean, while dynamic sea ice motion driven by northward winds further reduces sea ice concentration.
Linghan Li et al.
Status: final response (author comments only)
- CC1: 'Comment on egusphere-2022-36', Marte Hofsteenge, 28 Apr 2022
RC1: 'Comment on egusphere-2022-36', Pengfei Zhang, 28 Apr 2022
- AC1: 'Reply on RC1', Linghan Li, 04 Jul 2022
RC2: 'Comment on egusphere-2022-36', Anonymous Referee #2, 16 May 2022
- AC2: 'Reply on RC2', Linghan Li, 04 Jul 2022
Linghan Li et al.
Linghan Li et al.
Viewed (geographical distribution)
Linghan et al present an analysis of two summer atmospheric river (AR) events that coincide with two summers of extreme low Arctic sea ice extent. In addition to these two case studies the authors present a statistical analysis on atmospheric moisture related to AR’s and Arctic sea ice tendency and surface energy fluxes based on 40 years of ERA5 reanalysis data. The paper discusses a relevant topic that can improve the understanding of the drivers of Arctic sea ice variability, but in which way this research adds to previous research on Arctic sea ice extremes could be articulated more clearly. Some of the goals stated in the introduction are not met and therefore need rephrasing. While interesting results and nice visualisations of them are presented, some more explanation and interpretation of the results should clarify the point that the authors want to make. A more detailed discussion on how the methods and results of this study compare to previous studies related to sea ice extremes and atmospheric moisture input would help show the novelty of the presented study. I will elaborate on this with a few major comments, followed by minor comments.
The introduction section starts well with a discussion of Arctic sea ice variability and the role that atmospheric rivers and their input of moisture towards the Arctic can play on these sea ice changes. However, the research gap that the authors try to fill is left very generic and unclear (r 36-40). It misses reflection on previous studies that describe the role between atmospheric moisture input and sea ice anomalies and how the approach used in this study is different. Previous studies have focused on convergence of atmospheric moisture or latent energy transport calculated from ERA5/Interim products and their impact through energy balance components on the Arctic surface temperatures and sea ice as well. Can the authors clarify in which way the atmospheric river approach used in this study is different to previous studies and what is the added value of using this approach?
The goal of the study ‘to explore how AR’s influence Arctic sea ice variations’ (r 51) is very generic and needs some refinement. The authors nicely introduce what kind of results we can expect from this study (results from the 2 case studies and the statistical analysis over a long time period), but reflection on why this approach is chosen is missing. What is exactly the authors goal of the 2 case studies?
In the introduction the authors mention ‘This study investigates the relative contribution of surface heat flux components and the relative importance of thermodynamic and dynamic processes in sea ice changes when ARs happen in the Arctic.’ While this is a very relevant aim, which to this reviewer’s knowledge has not been answered in the current literature yet, it is not clear in the current manuscript whether the authors answer this question with the presented results. The authors show that both wind anomalies as well as anomalies in the surface energy fluxes coincide with AR events, however analysis or quantification on their relative contribution is not presented. While the wind fields suggest that there might be sea ice motion, no sea ice motion data products are analysed to show whether these surface winds indeed resulted in sea ice motion.
The authors show an extensive statistical analysis of concurrence of extreme atmospheric moisture content with the surface energy balance fluxes and sea ice changes. The explanation on choices that are being made for this analysis and what the main message is from this analysis are not clearly given. Previous studies have shown a delayed impact of moisture on the sea ice (e.g. Kapsch et al 2009, Hofsteenge et al 2022), which is not considered in this study used correlation analysis. Could the authors justify this choice and explain why the analysis will focus on short time scales? Adding significance to the maps of correlation coefficients would strengthen this analysis as well.
The authors have chosen to include interpretation and discussion of the results within the results section, which can work well for the presented study. However, further explanation of the presented results would improve the impact of the research. In particular, the results could be brought into context with previous studies more clearly. Some references that could be helpful to bring this paper into context are provided in a list below; it would be interesting if the authors could comment on whether they have any idea whether there is a delayed response of ARs on the sea ice. Lastly, the discussion of these results with previous papers on the role of atmospheric moisture or other factors driving the 2012 and 2022 sea ice minima could be improved. How do the results agree with previous research, and what findings are new or contrasting to the previous studies?
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