08 May 2023
 | 08 May 2023
Status: this preprint is currently under review for the journal TC.

Relevance of warm air intrusions for Arctic satellite sea ice climatologies

Philip Rostosky and Gunnar Spreen

Abstract. Winter warm air intrusions entering the Arctic ocean can strongly modify the microwave emission of the snow/ice system due to temperature induced snow metamorphism and ice crust formations e.g., after melt-refreeze events. Common microwave radiometer satellite sea ice concentration retrievals are based on empirical models using the snow/ice emissivity and thus can be influenced by strong warm air intrusions. Here, we carry out a long-term study analyzing 41 years of sea ice concentration observations from different algorithms to investigate the impact of warming events on the retrieved ice concentration. Our results show that three out of four analyzed sea ice concentration retrievals underestimate the sea ice concentration during warm air intrusions which increase the 2 m air temperature above -5 °C.

This can lead to sea ice area underestimations in the order of 104 to 105 km2. If the 2 m temperature during the warm air intrusions cross -2 °C, all retrieval methods are impacted. Our analysis shows that the strength of these strong warm air intrusions increased in recent years, especially in April. Within the scope of future climate change, it is expected that such warm air intrusions will occur even more frequent and also earlier in the season and thus the influence of these warm air intrusions on sea ice climatologies will become more important in future.

Philip Rostosky and Gunnar Spreen

Status: open (until 03 Jul 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2023-69', Anonymous Referee #1, 31 May 2023 reply

Philip Rostosky and Gunnar Spreen

Philip Rostosky and Gunnar Spreen


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Short summary
During winter, storms entering the Arctic ocean can bring warm air into the cold environment. Strong increases in air temperature modify the characteristic of the Arctic snow and ice cover. The Arctic sea ice cover can be monitored by satellites observing the natural emission of the earth's surface. In this study, we show that during warming, the change in the snow characteristic influences the satellite derived sea ice cover leading to a false reduction of the estimated ice area.