Polar Climate Change as Manifest in Atmospheric Circulation

Abstract

Purpose of ReviewDynamic manifestations of climate change, i.e. those related to circulation, are less well understood than are thermodynamic, or temperature-related aspects. However, this knowledge gap is narrowing. We review recent progress in understanding the causes of observed changes in polar tropospheric and stratospheric circulation, and in interpreting climate model projections of their future changes.Recent FindingsTrends in the annular modes reflect the influences of multiple drivers. In the Northern Hemisphere, there appears to be a “tug-of-war” between the opposing effects of Arctic near-surface warming and tropical upper tropospheric warming, two predominant features of the atmospheric response to increasing greenhouse gases. Future trends in the Southern Hemisphere largely depend on the competing effects of stratospheric ozone recovery and increasing greenhouse gases.SummaryHuman influence on the Antarctic circulation is detectable in the strengthening of the stratospheric polar vortex and the poleward shift of the tropospheric westerly winds. Observed Arctic circulation changes cannot be confidently separated from internal atmospheric variability.

New York City Panel on Climate Change 2019 Report Chapter 2: New Methods for Assessing Extreme Temperatures, Heavy Downpours, and Drought

“…There has been much debate whether such events are linked to the gradual melting of sea ice in the Arctic, and it appears that the answer is that there is a link (Overland et al ., ; Screen et al ., ). This was shown in climate models (Zhang et al ., ) and is consistent with the observation that polar vortex events are on the rise (Kretschmer et al ., ).…”

“…These events were connected to stratospheric warming, where the low-pressure vortex that is usually centered on the North Pole moves equatorward. This change in circulation is communicated down to the troposphere and results in anomalous weather situations during the winter season (Kretschmer et al, 2018;Screen et al, 2018).…”

An integrated index of recent pan-Arctic climate change

“…Atmospheric circulation does not play an important role in long term Arctic change as do temperature related increases. This separation of atmospheric circulation forcing from temperature forcing of Arctic change was also noted by Screen et al (2018) and references there in. Factor Analysis based on the covariability matrix is a suitable objective method to establish a composite ACCI.…”

Trends in cyclones in the high‐latitude North Atlantic during 1979–2016

“…The strength and orientation of the storm track reflect the large‐scale state of the atmosphere. The question how large‐scale atmospheric flow patterns have and will change in a rapidly warming climate has drawn a lot of attention in recent years (Screen et al ., and references within). Further, as Shepherd () writes, “we have much less confidence in the atmospheric circulation aspects of climate change [compared to the thermodynamic aspect], which are primarily controlled by dynamics and exert a strong control on regional climate”.…”