Eurasian Cooling Linked to the Vertical Distribution of Arctic Warming

Abstract

Observations show that deep Arctic winter warming, extending from surface to mid-troposphere, has concurred with below-average temperature over central Eurasia. Modeling studies focusing on the response to Arctic sea ice loss have shown Arctic surface warming but no consistent atmospheric changes at midlatitude. Using a large number of simulations from coupled and uncoupled climate models, we show that Eurasian below-average temperatures are more frequent in winters with deep warming compared to shallow, near-surface warming over the Barents-Kara Seas. Dramatic weakening of the midlatitude jet stream and increase in Ural blocking frequency are more likely to occur in winters with deep Arctic warming. Deep warming is independent of sea ice forcing but follows increased poleward atmospheric energy and moisture advection from the North Atlantic to the Arctic, indicating that internal natural variability and not sea ice is the main driving forcing for deep Arctic warming-cold Eurasia pattern in historical simulations.Plain Language Summary Observations show that the amplitude of Earth surface warming since the mid-twentieth century over the Arctic is more than twice as large as that of the global average. At the same time Eurasia has seen many extreme cold winters. Previous modeling studies have reached no consensus on whether the Arctic warming is influencing the Eurasian winter climate or not. Here we demonstrate that the simulated Arctic warming events are very different in their vertical extension and that Eurasian cold winters are more frequent when there is an Arctic warming aloft. This is caused by enhanced heat and moisture transport from the North Atlantic.

Warm Arctic, Cold Siberia Pattern: Role of Full Arctic Amplification Versus Sea Ice Loss Alone

“…Our results are consistent with Xu et al (2019) and He et al (2020), who found that the vertical extent of warming over the Barents‐Kara Seas can help resolve differences in the strength of Arctic‐midlatitude linkages in historical simulations. While we primarily make use of one model (WACCM), we find that atmospheric thickness is also closely coupled to the Siberian High response in E3SM (Figure 4).…”

“…It remains an open question how important the vertical extent of the tropospheric warming is in assessing Arctic-midlatitude teleconnections (He et al, 2020). This also has implications for improving our understanding of the intermodel spread of the eddy-driven jet response in the latest Coupled Model Intercomparison Project (CMIP) projections due to the competing "tug-of-war" effects between upper troposphere tropical warming and AA (Barnes & Polvani, 2015;Peings et al, 2018Peings et al, , 2019Vavrus, 2018;Zappa et al, 2018); although the amplification of tropical warming remains uncertain in model simulations (Santer et al, 2017).…”

“…We find that climate models prescribed with only Arctic sea ice loss do not fully capture the vertical extent of warming in the atmosphere, and thus underestimate the linkage between projected Arctic amplification and Eurasian climate.Recent work (e.g., Francis & Vavrus, 2015) has suggested that AA has led to a weakening of the midlatitude westerlies and an increase in the frequency of high-amplitude planetary wave regimes due to decreases in the latitudinal temperature gradient. Further, deep tropospheric warming may be important in resolving the mechanisms driving the "warm Arctic, cold Siberia" temperature anomaly pattern (He et al, 2020;Xu et al, 2019), and there is also evidence that the Arctic-midlatitude teleconnection is sensitive to the depth of vertical warming in idealized models (Sellevold et al, 2016). While it is currently not possible to attribute the continental cold extremes and atmospheric waviness to specific forcing due to the short observational record and substantial internal variability (…”

Increased persistence of large-scale circulation regimes over Asia in the era of amplified Arctic warming, past and future

“…The vast majority of studies based on reanalysis data support an association between amplified Arctic warming (AAW) and changes in the large-scale circulation that are consistent with slower-moving planetary waves, while investigations using model simulations are split as to whether a robust connection exists 5 . What is abundantly clear, however, is that challenges remain in identifying cause-and-effect because the signal-to-noise ratio is small, many changes are happening simultaneously in the climate system, models tend to underestimate the atmospheric response 6 , 7 , and model physics critical to the linkage may be unrealistic or missing 8 . Meanwhile, the controversy about the Arctic’s role in changing midlatitude weather continues, as some new studies report little atmospheric response to AAW 9 , 10 while others identify a robust response 5 .…”

Roles of Sea Surface Temperature Warming and Loss of Arctic Sea Ice in the Enhanced Summer Wetting Trend Over Northeastern Siberia During Recent Decades

“…The lower boundary conditions in the SIC‐EXP simulation capture the observed changes in Arctic sea ice and the changes in Arctic SST that are directly associated with the changes in sea ice but do not capture SST changes that are not directly related to variations in sea ice. Previous studies have suggested that the atmospheric response is weaker than in the real world by only taking the direct effects of SSTs and SIC changes into account, without considering the interactions and feedbacks between these variables (Deser et al, 2015; He et al, 2020; Mori et al, 2019).…”