Ice Sheet Expansion in the Cretaceous Greenhouse World

Abstract

Globally elevated temperatures during the Cretaceous extreme greenhouse climate interval were punctuated by the Valanginian Weissert event, which was characterised by a positive carbon isotope excursion, global cooling, and a glacial event approximately at 135 Ma. The inability to disentangle ocean temperature and continental ice volume trends hinders our understanding of these climate fluctuations in deep-time. We investigated the ocean temperature–ice sheet dynamics of glaciation events that occurred in the Cretaceous greenhouse world. New clumped isotope and δ18O data from sits in the Tethyan Ocean show that seawater temperatures decreased by 5°C–6°C, consistent with the development of glacial periods, and maximum ice volumes about half the size of present-day Antarctica. This cooling event provides a counter-example to other Mesozoic climate transitions driven by changes in atmospheric greenhouse gas contents. Our results suggest a robust coupling between mid-latitude seawater temperatures and polar ice volume as atmospheric CO2 contents decline.

Inhibition of VCAM-1 gene transcriptional blockade by RHOdiroside through inhibition of P65 and CSN5 deubiquitination reduces atherosclerosis in monocytes and endothelial adherent cells

“…In animal models, RHO has been demonstrated to reduce the levels of VCAM-1, ICAM-1, and MCP-1 in plaques. Moreover, RHO exhibits the ability to decrease MMP2 and MMP9 levels by upregulating tissue MMP2 inhibitors [21] . Additionally, RHO can enhance collagen content within plaques, thereby promoting plaque stability.…”

Sedimentary deposits and bioturbation in an Early Cretaceous subarctic stormy greenhouse shelf environment

“…The Early Cretaceous Svalbard had a generally warm-temperate humid climate (estimated mean annual temperatures of 7-10°C) that supported an ornithopod dinosaur population, deciduous conifers, ginkgos and local peat accumulation forming coal seams (Heintz 1963;Edwards et al 1978;Steel and Worsley 1984;Nemec 1992;Hurum et al 2006). However, the Aptian regional marine transgression in Svalbard area opened the Barents Shelf to the adjacent Arctic Ocean (Steel and Worsley 1984;Blakey 2011), whereby the epicontinental sea with its relatively warm waters became subject to a harsh Arctic wave climate and transient incursions of cold bottom water from spells of polar glacial temperatures (Weissert and Lini 1991;Maher et al 2004; Kessels et al 2006; Price and Nunn 2010; Price and Passey 2013; Wang et al 2022). These physical conditions amounted to a speci c type of shelf environment, thus far little documented in the global stratigraphic record.…”