Abrupt Ice Age Shifts in Southern Westerlies and Antarctic Climate Forced from the North

The Southern Hemisphere (SH) mid-latitude westerly winds play a central role in the global climate system via Southern Ocean upwelling, carbon exchange with the deep ocean, Agulhas Leakage, and Antarctic ice sheet stability. Meridional shifts in the SH westerlies have been hypothesized in response to abrupt North Atlantic Dansgaard-Oeschger (DO) climatic events of the last ice age, in parallel with the well-documented shifts of the intertropical convergence zone. Shifting moisture pathways to West Antarctica are consistent with this view, but may represent a Pacific teleconnection pattern. The full SH atmospheric-circulation response to the DO cycle, as well as its impact on Antarctic temperature, have so far remained unclear. Here we use five volcanically-synchronized ice cores to show that the Antarctic temperature response to the DO cycle can be understood as the superposition of two modes: a spatially homogeneous oceanic “bipolar seesaw” mode that lags Northern Hemisphere (NH) climate by about 200 years, and a spatially heterogeneous atmospheric mode that is synchronous with NH abrupt events. Temperature anomalies of the atmospheric mode are similar to those associated with present-day Southern Annular Mode (SAM) variability, rather than the Pacific South America (PSA) pattern. Moreover, deuterium excess records suggest a zonally coherent migration of the SH westerlies over all ocean basins in phase with NH climate. Our work provides a simple conceptual framework for understanding the circum-Antarctic temperature response to abrupt NH climate change. We provide observational evidence for abrupt shifts in the SH westerlies, with ramifications for global ocean circulation and atmospheric CO₂. These coupled changes highlight the necessity of a global, rather than a purely North Atlantic, perspective on the DO cycle

The City Is not Innocent: Homelessness and the Value of Urban Parks

This paper builds on contemporary memoirs of homelessness from cities across the United States to develop a more nuanced understanding of the use value of urban parks and green spaces. Based on analysis of over seventy memoirs, we synthesize the writings of nine memoirists who examine their relationship to green spaces in cities. Instead of framing nature as something pristine and distinct from society—or something dangerous and untamed—these writings portray urban green spaces as sites of belonging and everyday life. In the US today, cities often either value parks as playgrounds for middle-class leisure or devalue them as targets of racialized anti-homeless policing. In both instances, parks are framed in relation to their impact on the exchange value of surrounding urban areas. In contrast, the memoirs of homelessness we examine portray parks and other green spaces as enabling privacy, survival, and emotional solace in an urban landscape often marked by surveillance, deprivation, and violence. These crucial values reveal a new conceptualization of urban parks as profoundly useful to those who are subject to the exclusions of capitalist property