Past and Future Changes in the Arctic Oscillation

11/17/20222 min read

Within the climate system, there are oscillatory large-scale phenomena which manifest as regular fluctuations of “global- or regional scale climate variables” (de Viron et al, 2013).

In ERA20C from 1900 to2010, the Arctic Oscillation (“AO”) has experienced a “negative trend (approximately −6 hPa per century) in mean-sea level pressure (MSLP)” (Bloomfield et al, 2018). In the past 40 years, “[global] and Arctic land-ocean temperatures have increased” (Kumar et al, 2020). A reduction in sea level pressure, or, the “atmospheric pressure at mean sea level” (AMS), indicates an increase in sea surface temperatures. This negative trend is “consistent with increases in wintertime storminess seen in ERA20C over the North Atlantic and North Pacific” (Bloomfield et al, 2018).

In recent decades, “a trend toward lower pressure over the poles, higher pressure in the mid-latitudes, and stronger sub-polar westerlies indicated a more persistent positive phase of the AO” (Givati and Rosenfeld, 2013), as “positive values for 1989-present” are observed (JISAO).

As global average surface temperatures continue to rise, it is likely that this trend will continue unabated.

“When the AO is strongly positive, a strong mid-latitude jet stream steers storms northward, reducing cold air outbreaks in the mid-latitudes” (Climate.gov, 2009). The “positive phases of the AO have also been shown to warm midlatitude continental interiors and drastically reduce the Arctic Ocean’s ice cover,” and are “associated with stratospheric cooling and increased levels of greenhouse gases” (Zhang et al, 2021).

In that case, we can expect more deglaciation and loss of Arctic snow cover. Melting permafrost and the decline in Arctic sea ice also decreases albedo and release methane and black carbon, which combine to exacerbate the enhanced greenhouse effect. Further, this development “[threatens] the survival of animals up and down the food chain” (IISD, 2022).

(292 words)

References: