Impact of Winter Ural Blocking on Arctic Sea Ice: Short-Time Variability

Abstract

Using daily reanalysis data from 1979 to 2015, this paper examines the impact of winter Ural blocking (UB) on winter Arctic sea ice concentration (SIC) change over the Barents and Kara Seas (BKS). A case study of the sea ice variability in the BKS in the 2015/16 and 2016/17 winters is first presented to establish a link between the BKS sea ice variability and UB events. Then the UB events are classified into quasi-stationary (QUB), westward-shifting (WUB), and eastward-shifting (EUB) UB types. It is found that the frequency of the QUB events increases significantly during 1999–2015, whereas the WUB events show a decreasing frequency trend during 1979–2015. Moreover, it is shown that the variation of the BKS-SIC is related to downward infrared radiation (IR) and surface sensible and latent heat flux changes due to different zonal movements of the UB. Calculations show that the downward IR is the main driver of the BKS-SIC decline for QUB events, while the downward IR and surface sensible heat flux make comparable contributions to the BKS-SIC variation for WUB and EUB events. The SIC decline peak lags the QUB and EUB peaks by about 3 days, though QUB and EUB require lesser prior SIC. The QUB gives rise to the largest SIC decline likely because of its longer persistence, whereas the BKS-SIC decline is relatively weak for the EUB. The WUB is found to cause a SIC decline during its growth phase and an increase during its decay phase. Thus, the zonal movement of the UB has an important impact on the SIC variability in BKS.

Ural Blocking Driving Extreme Arctic Sea Ice Loss, Cold Eurasia, and Stratospheric Vortex Weakening in Autumn and Early Winter 2016–2017

“…Such westward propagation of blocking during winter (link 7, Figure ) has been documented in previous studies. Chen et al () described cases of blocking anomalies with sufficient amplitude to propagate westward against the eastward flow (see also Luo et al, ; Yao et al, ). The weakening of the stratospheric polar vortex in November 2016 might have impacted the midlatitude wave guide on a hemispheric scale by weakening the westerly flow and allowing BE of the Urals to retrogress into Europe in December 2016 and January 2017.…”

“…In many studies UB is defined as blocking occurring over the sector 30-90 • E (e.g., Chen et al, 2018) or 40-80 • E (e.g., Gong & Luo, 2017;Luo et al, 2016a). However, often, the Ural sector is loosely defined and extends beyond the above mentioned domain.…”

“…Thus, the impact of UB on SIC over the BKS was not limited to autumn 2016. Although Chen et al () established a link between UB and enhancing SIC deficit over the BKS during November 2016 (link C1‐B3), they did not provide evidence (their Figure 1b) for the late December 2016 SIC deficit (link B4‐C2). In our study, BE was identified to the east of 40° E (Figure e), which was not identified by their algorithm.…”

Weak Stratospheric Polar Vortex Events Modulated by the Arctic Sea‐Ice Loss

“…The influences of blocking in the Ural region on the climate have been discussed. Chen et al () pointed out that quasi‐stationary Ural Blocking contributes to a reduction in the BKS sea ice. Our light‐ice composite also has a feature resembling Ural Blocking, for example, anticyclonic anomalies around the BKS (see Figure b).…”

Anomalous winter moisture transport associated with the recent surface warming over the Barents–Kara seas region since the mid‐2000s

“…Several recent studies argued that the ice-albedo feedback is unimportant for recent winter Arctic warming, whereas the enhanced downward infrared radiation (IR) is more important for the winter Arctic warming and sea ice loss both on the intra-seasonal and interannual time scales (Doyle et al, 2011;Woods et al, 2013;Park et al, 2015;Woods and Caballero, 2016;. Furthermore, the enhanced water vapour injection from outside the Arctic was used to explain the intensified downward IR anomalies on the intra-seasonal or interannual time scales (Woods et al, 2013;Woods and Caballero, 2016;Luo et al, 2016a;Luo et al, 2016b;Chen et al, 2018;Zhong et al, 2018). In particular, Woods et al (2013) and Woods and Caballero (2016) found that the enhanced poleward moisture intrusion is often located on the western side of a blocking anticyclone.…”