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Siberia saw a heat wave of extreme monthly temperatures of +6°C anomalies from January through May 2020, culminating with near daily temperature records at the Arctic station of Verhojansk in mid‐June. This was a major Arctic event. The proximate cause for the warm extremes from January through April was the record strength of the stratospheric polar vortex (SPV) and tropospheric jet stream. The SPV and high geopotential heights to the south combined to provide strong zonal winds from the west that reduced the potential penetration of cold air from the north. An index of vortex strength is the Arctic Oscillation (AO); averaged over January–April, the AO set extreme positive records in 1989, 1990, and 2020 (baseline starting in 1950). The strength and stability of the SPV over the central Arctic contributed to the winter–spring persistence of the heat wave in Siberia. May–June temperatures were related to high tropospheric geopotential heights over Asia. An open question is whether these dynamic events are becoming more persistent. Such record events will not occur every year but one can expect that they will occasionally naturally reoccur over the next decades due to internal atmospheric variability in addition to a continued global warming background. [ABSTRACT FROM AUTHOR]

Data on surface solar radiation are scarce in high‐latitude regions, and few studies have evaluated the performance of reanalysis products in estimating solar radiation in those regions. Here, an extensive solar radiation dataset is compiled from 98 stations across Alaska to evaluate 11 different surface solar radiation products (seven reanalysis and four observation‐derived). No product can capture all aspects of the ground‐based observations, and there is ample room for improvement; root mean square errors (RMSEs) of daily, monthly, and annual average comparisons of the products against observations are 38–65, 19–39, and 11–17 W⋅m−2, respectively. ERA5, MERRA2, and ERA‐Interim performed the best in Alaska. Daily records from all products show large RMSEs of 60–108 W⋅m−2 during May–July, equivalent to 30–55% of the observed solar radiation during this season. The sparseness of Alaskan observations, cloud cover, and algorithm issues may be potential sources of bias. [ABSTRACT FROM AUTHOR]

There is growing recognition that reductions in Arctic sea ice extent will influence patterns of atmospheric circulation both within and beyond the Arctic. We explore the impact of 2007 ice conditions (the second lowest Arctic sea ice extent in the satellite era) on atmospheric circulation and surface temperatures and fluxes through a series of model experiments with the NCAR Community Atmospheric Model version 3 ( CAM3). Two 30-year simulations were performed; one using climatological sea ice extent for the end of the 20th century and other using observed sea ice extent from 2007. Circulation differences over the Northern Hemisphere were most prominent during autumn and winter with lower sea level pressure ( SLP) and tropospheric pressure simulated over much of the Arctic for the 2007 sea ice experiment. The atmospheric response to 2007 ice conditions was much weaker during summer, with negative SLP anomalies simulated from Alaska across the Arctic to Greenland. Higher temperatures and larger surface fluxes to the atmosphere in areas of anomalous open water were also simulated. CAM3 experiment results were compared to observed SLP anomalies from the National Center for Environmental Prediction/National Center for Atmospheric Research ( NCEP/ NCAR) Reanalysis data. The observed SLP anomalies during spring are nearly opposite to those simulated. In summer, large differences were shown between the observed and simulated SLP also, suggesting that the sea ice conditions in the months preceding and during the summer of 2007 were not responsible for creating an atmospheric circulation pattern which favoured the large observed sea ice loss. The simulated and observed atmospheric circulation anomalies during autumn and winter were more similar than spring and summer, with the exception of a strong high pressure system in the Beaufort Sea which was not simulated, suggesting that the forced atmospheric response to reduced sea ice was in part responsible for the observed atmospheric circulation anomalies during autumn and winter. [ABSTRACT FROM AUTHOR]

ABSTRACT In this article, the results of an investigation into the atmospheric pressure conditions in the Arctic in the period from 1801 to 1920 are presented. For this period, which can be described as 'early instrumental', limited meteorological data exist from a network of regular stations. As a result, in order to get at least a rough idea of pressure conditions in the Arctic in the study period, data from different land and marine expeditions were collected. A total of 94 pressure series of monthly means have been gathered, the duration of which is usually less than 2 years. While the area and time periods covered by the data are variable, it is still possible to describe the general character of the pressure conditions. The results show that the areally averaged Arctic pressure in the early instrumental period (1861-1920) was 0.8 hPa lower than today (1961-1990). Lower values of atmospheric pressure were also observed in all study regions, excluding the Atlantic. The greatest negative differences (−2.1 hPa) have been found for the Canadian Arctic. The greatest changes between the historical and present times were noted in all winter months and in winter as a whole (−1.9 hPa), while in summer and autumn they were very small and their average differences came to − 0.1 and − 0.2 hPa, respectively. Comparison of historical and contemporary annual courses of atmospheric pressure in the whole of the Arctic and in its particular regions reveals general consonance. There is evidence to show that changes in Arctic atmospheric pressure during the whole study period were insignificant. Atmospheric pressure in the first International Polar Year (IPY) period (September 1882 to July 1883) was, on average, 1.4 hPa higher than in modern period (1961-1990). The greatest positive seasonal differences between historical and contemporary pressure values occurred in autumn (2.6 hPa), while the lowest were in winter (only 0.2 hPa). Spatial patterns of average annual and seasonal atmospheric pressure in the Arctic were very similar to present day ones. The pressure differences calculated between historical and modern mean monthly values show that almost all of them lie within one standard deviation from present long-term mean (1961-1990). Thus, this means that the atmospheric pressure in the early instrumental period was not significantly different to that of the present day. Recent, commonly used gridded datasets of the sea level atmospheric pressure (HadSLP2 and the 20th Century Reanalysis Project) reveal quite a large positive bias in the period 1850-1920 in comparison to the real data from the instrumental observations. Copyright © 2012 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

This article reports on the environmental and climatic changes and their causes in the Antarctic and Arctic. It discusses that there are continuing increases in surface temperatures, losses of sea ice and tundra, as well as warming of permafrost over areas of the Arctic, while most of the major increase in Antarctic temperatures is on the Antarctic Peninsula linked with sea ice loss in the Bellingshausen-Amundsen Seas sector. The synthesis of observational evidence leads to the conclusion that the Arctic changes of the past several decades are attributable to circulation-driven changes.