Massive volcanic eruptions could cause localised warming that might destabilise some of the world's biggest ice sheets, according to new research from Durham University.
Scientists investigated links between very large volcanic eruptions and polar temperatures during the last Ice Age.
Their findings suggest that some periods of Antarctic warming between 30,000 to 80,000 years ago were triggered by huge volcanic eruptions in the Northern Hemisphere that caused a shift in the world's weather patterns.
The Northern Hemisphere cooled as volcanic particles reflected the sun's heat, forcing warmer weather fronts south which led to warming in Antarctica, the researchers said.
Conversely, their research suggests that Southern Hemisphere eruptions could also have triggered abrupt warming in Greenland during the last Ice Age.
Evolution and dispersal of mammoths across the Northern Hemisphere
Authors:
Lister et al
Abstract:
le of species origins and dispersal, but understanding has been impeded by taxonomic confusion, especially in North America. The Columbian mammoth Mammuthus columbi was thought to have evolved in North America from a more primitive Eurasian immigrant. The earliest American mammoths (1.5 million years ago), however, resemble the advanced Eurasian M. trogontherii that crossed the Bering land bridge around that time, giving rise directly to M. columbi. Woolly mammoth M. primigenius later evolved in Beringia and spread into Europe and North America, leading to a diversity of morphologies as it encountered endemic M. trogontherii and M. columbi, respectively. In North America, this included intermediates (“M. jeffersonii”), suggesting introgression of M. primigenius with M. columbi. The lineage illustrates the dynamic interplay of local adaptation, dispersal, and gene flow in the evolution of a widely distributed species complex.
The De Geer, Thulean and Beringia routes: key concepts for understanding early Cenozoic biogeography
Author:
Brikiatis
Abstract:
Aim
I re-evaluate the specific biogeographical significance of each of the land bridges (Beringia, Thulean and De Geer) in the Northern Hemisphere during the latest Cretaceous–early Cenozoic, showing that the Thulean and De Geer routes did not operate contemporaneously.
Location
Northern Hemisphere landmasses.
Methods
I review the recent climatic, sea-level, geotectonic, palaeofloristic, and marine and terrestrial faunal data that have emerged since the establishment in the 1980s of the biogeographical concepts of the early Cenozoic Northern Hemisphere land bridges and present a synthesis supporting a revised scenario for early Cenozoic biogeographical development.
Results
Palaeogeographical and geotectonic data, supported by strong floral and faunal evidence, suggest that the palaeogeographical and chronological frames for the formation of all three land bridges are different from those originally proposed. Dispersal events via the causeways seem to have taken place during specific time intervals resulting from fluctuations in sea level and climate.
Main conclusions
The De Geer and Thulean routes were not contemporaneous. The former existed during the latest Cretaceous to the early Palaeocene, joining North America with Eurasia. The Thulean route became established well after the interruption of the De Geer route, offering a southerly connection between western Europe and North America in at least two episodes: c. 57 Ma and c. 56 Ma. The Bering route functioned in two warm periods: 65.5 Ma (coinciding with the De Geer route) and c. 58 Ma, during the Palaeocene (possible Eocene exposures are not considered here). The formation of the De Geer route explains faunal similarities between the Puercan and Torrejonian North American land mammal ages (NALMAs) and the Shanghuan Asian land mammal age (ALMA). The Thulean route explains faunal similarities between the Clarkforkian (Cf1) and Wasatchian (Wa0, 1) NALMAs, and the Cernaysian and Neustrian (PE I, II) European land mammal ages. The Bering route explains faunal similarities between the Gashatan ALMA and the Tiffanian (Ti5) NALMA.
