Impact of Polar Ozone Depletion on Subtropical Precipitation

Abstract

Over the past half-century, the ozone hole has caused a poleward shift of the extratropical westerly jet in the Southern Hemisphere. Here, we argue that these extratropical circulation changes, resulting from ozone depletion, have substantially contributed to subtropical precipitation changes. Specifically, we show that precipitation in the Southern subtropics in austral summer increases significantly when climate models are integrated with reduced polar ozone concentrations. Furthermore, the observed patterns of subtropical precipitation change, from 1979 to 2000, are very similar to those in our model integrations, where ozone depletion alone is prescribed. In both climate models and observations, the subtropical moistening is linked to a poleward shift of the extratropical westerly jet. Our results highlight the importance of polar regions on the subtropical hydrological cycle.

Global warming-accelerated drying in the tropics

“…In the extratropics, the increased thermodynamic stability and weaker latitudinal temperature gradient were expected to reduce extratropical baroclinic instability and eddies, leading to a poleward movement of the HC boundary (9)(10)(11). This "extratropical-driven" theory for the HC change has been further supported by the strong impact of the Antarctic ozone hole on the poleward expansion of the southern edge of the HC (12) and by a connection between northern hemispheric aerosols, especially black carbon, and the northward expansion of the HC northern edge (13).…”

“…The changes of HC intensity and width are sensitive to radiative cooling in the upper troposphere and stratosphere, sea surface temperature distributions, and land surface temperature changes, especially in the northern hemisphere (8,12,15). Different cloud and convective parameterizations appear to contribute to the intermodel discrepancies in modeled HC intensity and frequency (14).…”

Synchronous volcanic eruptions and abrupt climate change ∼17.7 ka plausibly linked by stratospheric ozone depletion

“…In Patagonia and New Zealand, warmer and dryer conditions south of ∼35°S (37) led to the well-documented retreat of glaciers (4-6) that starved glacial outwash plains of their fine-sediment resupply (45), with lower wind speeds possibly also contributing to reduced dustiness (47). In aridity-driven SH dust source regions located north of ∼35°S (Australia, Africa, extratropical South America), a cooler and wetter climate (37) sharply reduced aridity and hence dust export (9). Fourth, westerlies shifted poleward (SI Appendix, Fig.…”

“…These include a poleward shift and acceleration of the westerly winds around Antarctica (35), acceleration of midlatitude easterly winds (35), and southward expansion of the summertime Hadley cell, leading to changes in temperature and precipitation extending from the Antarctic Peninsula (36) to the subtropics, especially during austral summer (37). Specific climate changes include subtropical moistening and midlatitude drying (37) (Fig. 5), as well as pronounced warming in the northern Antarctic Peninsula and Patagonia, with cooling over the Antarctic continent, particularly in East Antarctica (35).…”

Towards predictive understanding of regional climate change

“…Ozone depletion in the southern polar stratosphere also contributes to poleward movement of the westerly jets and changes in subtropical precipitation patterns 44 .…”