Warm Arctic–Cold Eurasia pattern driven by atmospheric blocking in models and observations

Abstract

In recent decades, Arctic-amplified warming and sea-ice loss coincided with a prolonged wintertime Eurasian cooling trend. This observed Warm Arctic-Cold Eurasia pattern has occasionally been attributed to sea-ice forced changes in the midlatitude atmospheric circulation, implying an anthropogenic cause. However, comprehensive climate change simulations do not produce Eurasian cooling, instead suggesting a role for unforced atmospheric variability. This study seeks to clarify the source of this model-observation discrepancy by developing a statistical approach that enables direct comparison of Arctic-midlatitude interactions. In both historical simulations and observations, we first identify Ural blocking as the primary causal driver of sea ice, temperature, and circulation anomalies consistent with the Warm Arctic-Cold Eurasia pattern. Next, we quantify distinct transient responses to this Ural blocking, which explain the model-observation discrepancy in historical Eurasian temperature. Observed 1988-2012 Eurasian cooling occurs in response to a pronounced positive trend in Ural sea-level pressure, temporarily masking long-term midlatitude warming. This observed sea-level pressure trend lies at the outer edge of simulated variability in a fully coupled large ensemble, where smaller sea-level pressure trends have little impact on the ensemble mean temperature trend over Eurasia. Accounting for these differences bring observed and simulated trends into remarkable agreement. Finally, we quantify the influence of sea-ice loss on the magnitude of the observed Ural sea-level pressure trend, an effect that is absent in historical simulations. These results illustrate that sea-ice loss and tropospheric variability can both play a role in producing Eurasian cooling. Furthermore, by conducting a direct model-observation comparison, we reveal a key difference in the causal structures characterizing the Warm Arctic-Cold Eurasia Pattern, which will guide ongoing efforts to explain the lack of Eurasian cooling in climate change simulations.

Unique Temperature Trend Pattern Associated With Internally Driven Global Cooling and Arctic Warming During 1980–2022

“…At the same time, parts of the Arctic have been warming ∼7x faster than the global mean over 1980-2022, which may implicate the role of internally driven sea-ice decline associated with atmospheric circulation anomalies (e.g., Day et al, 2012;Ding et al, 2014;England et al, 2019;Isaksen et al, 2022;Roach & Blanchard-Wrigglesworth, 2022;Svendsen et al, 2021). Furthermore, many studies have indicated the potential connection between Arctic warming and Northern Hemisphere continental cooling and the role of internal variability (Blackport et al, 2019;Cohen et al, 2014;Fyfe, 2019;Kaufman et al, 2024;Palmer, 2014). Our study suggests that internal variability has made an important contribution to observed Arctic warming, Eastern Pacific cooling, and Southern Ocean cooling over 1980-2022.…”