Stratospheric influence on marine cold air outbreaks in the Barents Sea

Abstract

Abstract. Marine cold air outbreaks (MCAOs) in the Arctic are associated with a range of severe weather phenomena, such as polar lows, strong surface winds and intense cooling of the ocean surface. While MCAO frequency has been linked to the strength of the stratospheric polar vortex, a connection to the occurrence of extreme stratospheric events, known as sudden stratospheric warmings (SSWs), has dominantly been investigated with respect to cold extremes over land. Here, the influence of SSW events on MCAOs in the Barents Sea is studied using observational and reanalysis datasets. Overall, more than a half of SSW events lead to more frequent MCAOs in the Barents Sea. SSW events with an enhanced MCAO response in the Barents Sea are associated with a ridge over Greenland and a trough over Scandinavia, leading to an anomalous dipole pattern of 500-hPa geopotential height and strong northerly flow over the Norwegian Sea. As SSW events tend to have a long-term influence on surface weather, these results can shed light on the predictability of MCAOs in the Arctic for winters with SSW events.

Predictors and prediction skill for marine cold‐air outbreaks over the Barents Sea

“…The time lag between the inflow of ocean temperature anomaly through the Barents Sea opening and the associated changes in sea‐ice cover downstream was reported to be one month (Lien et al ., 2017, and references therein). Additionally, the stratosphere was proposed to drive the Barents Sea MCAOs within one month after SSW events (Afargan‐Gerstman et al ., 2020). In this section, we first evaluate the relationship between these large‐scale conditions and the Barents Sea MCAOs.…”

“…While, Papritz and Grams (2018) did not confirm that the strength of the polar vortex systematically affected MCAO frequency in the Nordic Seas, Afargan‐Gerstman et al . (2020) show that more than half of SSW events in the ERA‐Interim atmospheric reanalysis are associated with MCAOs in the Barents Sea. In their study, SSW events with an enhanced MCAO response in the Barents Sea are also linked with a ridge over Greenland and a trough over Scandinavia.…”

“…Marine cold‐air outbreaks (MCAOs) are surges of cold air escaping from the inner Arctic and becoming exposed to the relatively warm ocean surface (Rasmussen, 1983). MCAOs over the Nordic Seas usually occur within the northerly flow associated with large‐scale anomalous anticyclonic circulation over Greenland and anomalous cyclonic circulation over Scandinavia (Kolstad et al ., 2009; Mallet et al ., 2013; Papritz and Grams, 2018; Afargan‐Gerstman et al ., 2020). Given the importance of MCAOs for the formation of severe weather events such as polar lows (PLs; Rasmussen, 1983; Kolstad, 2011; Landgren et al ., 2019), and for driving the ocean convection in the North Atlantic (Kolstad and Bracegirdle, 2008), we evaluate predictability of MCAOs using a seasonal prediction system and by identifying MCAO precursors.…”

“…Using a causal discovery approach, we aim to test potentially causal relationships between the Barents Sea MCAOs and their environmental conditions. These factors include atmospheric circulation patterns enabling cold air flow from the Arctic region (Mallet et al ., 2013; Papritz and Grams, 2018; Afargan‐Gerstman et al ., 2020), sea surface temperature changes as a proxy for ocean‐to‐air heat loss (Lien et al ., 2017) available to erode or fuel MCAOs, as well as sea ice concentration regulating the region of MCAO occurrence (Kolstad and Bracegirdle, 2008). Knowing causal precursors can then help to improve predictions of MCAOs as was shown by Dobrynin et al .…”

Comment on wcd-2021-20

“…Characterizing MCAOs by simple diagnostic indices and understanding the link between MCAOs and PLs is an area of active research with relevance for improving seasonal predictions and climatological analyses. Various interdependent factors play a role in the genesis of MCAOs and PLs (Claud et al, 2007;Kolstad and Bracegirdle, 2008;Kolstad, 2011;Terpstra et al, 2016;Afargan-Gerstman et al, 2020;Stoll et al, 2021). MCAOs have been reported to be a necessary, but not a sufficient condition for the occurrence of PLs (Kolstad, 2011).…”