Abstract
Marine Cold-Air Outbreaks (MCAO) can be used as a large-scale measure of the potential for development of Polar Lows in the Northern North Atlantic Ocean during NH winter. We applied an MCAO index to 30 members of the Community Earth System Model Large Ensemble to investigate model-projected future changes in the Nordic and Barents Seas in response to anthropogenic climate change. In agreement with previous studies we found an overall decrease in the MCAO index due to increased tropospheric static stability. We also found a changed seasonal profile, with a stronger decrease in December–January than in February–March, effectively leading to the peak occurring in February rather than January in the Nordic Seas. In the Barents Sea, the reductions were only statistically significant in the autumn and spring, with the winter reduction due to increased static stability was partly balanced by a retracting sea-ice edge. The contribution from circulation changes in mean sea-level pressure was assessed by a cluster analysis in lower-dimensional phase-space, spanned by the projections onto the four leading Empirical Orthogonal Functions. While there was a small but statistically significant increase of the Atlantic Ridge-like pattern, the overall changes in MCAO were dominated by changes in temperature at the sea surface and aloft.
Highlights
When a cold air mass, typically originating from an icecovered sea area, is advected over open water, a large flux of latent heat is triggered from the ocean to the atmosphere, due to the much higher temperature of the water
For CESM1, Park et al (2014) found that these biases are mostly of radiative origin related to clouds
The focus of this study is, on open water areas in the Nordic Seas and Barents Sea, over which both the SKT and 850 biases are relatively small (− 1 to + 1 K are shown in grey)
Summary
When a cold air mass, typically originating from an icecovered sea area, is advected over open water, a large flux of latent heat is triggered from the ocean to the atmosphere, due to the (relatively) much higher temperature of the water This pattern is called a Marine Cold-Air Outbreak (MCAO, Kolstad and Bracegirdle 2008; Mansfield 1974), and is important for the formation of small-scale, marine cyclones, polar lows (PL), which cause severe weather conditions that combine strong winds with heavy snow-fall and freezing sea-spray at the high latitudes. This is partly due to the high computational resources associated with running a climate model for hundreds of years This makes it difficult to adequately quantify the internal variability, and to separate it from the response to different external forcing applied in the future scenario or from the spread due to model uncertainty.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
