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Climate Change: Polar Regions
Published in Yeqiao Wang, Atmosphere and Climate, 2020
During the Last Glacial Maximum (LGM) approximately 25-18 ka vast ice sheets covered much of North America and Fennoscandia, extending to the British Isles. In North America, the Canadian Arctic Archipelago was occupied by the Innuitian ice sheet, the western cordilleras by the Cordilleran ice sheet, and most of central and eastern Canada and the northern United States by the 3 km thick Laurentide ice sheet. The locking up of water in the ice sheets led to a drop in the sea level of approximately 130 m. Consequently, continental shelves were exposed, particularly in the Arctic, and a Bering land bridge formed, enabling humans to enter Alaska from eastern Siberia. Permafrost developed in the sediments of the exposed shelves and this persists extensively in the Laptev and East Siberia seas at present. Global mean temperature during the LGM was approximately 6°C below that in the twentieth century. In Beringia, July temperatures were approximately 4°C lower than late twentieth century.
Key questions on the evolution and biogeography of New Zealand alpine insects
Published in Journal of the Royal Society of New Zealand, 2022
Thomas R. Buckley, Robert J. B. Hoare, Richard A. B. Leschen
A further impact of the Pliocene and Pleistocene cooling was the development of large glaciers. At the Last Glacial Maximum (LGM, 30–18 ka), the Southern Alps contained approximately 6800 km3 of ice of which less than 1% remains today (James et al. 2019). During the glacial maxima of the Pleistocene, valley glaciers, piedmont glaciers and high altitude ice fields formed creating a near-continuous ice cover extending 700 km along the Southern Alps (Fitzsimons and Veit 2001; Golledge et al. 2012). Air temperatures in the Southern Alps were 5–6°C cooler than today, but during earlier interglacials, mean temperatures were similar to those of today (Golledge et al. 2012). The LGM glaciers scoured large valleys, especially in western areas, and at their peak acted as significant biogeographic breaks for less mobile species (Wardle 1963). The large outwash plains and moraines associated with the glaciers also acted as biogeographic barriers as these substrates are typically unstable, low in nutrients for plant growth and, therefore, unsuitable for many species. These large glaciers and their associated landforms excluded many species, until their retreats during interglacial periods. At these time points significant new areas of habitat opened allowing colonisation and likely facilitating speciation (McGlone 1985). Today, the glaciers are of relatively small extent and in 2016 covered an area of 794 ± 34 km2 (Baumann et al. 2021).
Peesey Swamp—a Last Interglacial (MIS 5e) marine corridor across southern Yorke Peninsula, southern Australia
Published in Australian Journal of Earth Sciences, 2021
T.-Y. Pan, C. V. Murray-Wallace, R. P. Bourman, A. García
During the Last Interglacial Maximum, the sea flooded the entire Peesey Swamp and Marion Lake regions in southern Yorke Peninsula, with the two seaways connecting southern Spencer Gulf with Investigator Strait, when sea-level reached its maximum elevation (i.e. <5 m AHD). With the onset of the last glacial cycle, following the end of the Last Interglacial Maximum, sea-level fell, culminating at approximately 125 m below present sea-level during the Last Glacial Maximum (Yokoyama et al., 2000, 2001). During the entire glacial cycle, the lowland of the Peesey Swamp region was subaerially exposed, and saline lakes developed within the lowland depression up to the present day. In addition, the MIS 5e shelly marine successions within Peesey Swamp underwent pedogenesis and karstification, forming consolidated calcretes on the upper portion of the Glanville Formation (Morris, 1993).
The pollen record from marine core MD03-2607 from offshore Kangaroo Island spanning the last 125 ka; implications for vegetation changes across the Murray-Darling Basin
Published in Australian Journal of Earth Sciences, 2021
P. De Deckker, S. van der Kaars, S. Haberle, Q. Hua, J.-B. W. Stuut
As already shown by Gingele et al. (2004, 2007) and Gingele and De Deckker (2005a), this core contains a record of fluvial clays from the River Murray deposited at sea. It is located close to the edge of the continental shelf and the nature of the sediment will change depending on the proximity of the core site to the continent’s edge/shoreline. Based on the Lambeck et al. (2014) global sea-level reconstructions, this boundary varied between ∼200 km today from the Murray Mouth and approximately 15 km during the lowest sea-level experienced during the Last Glacial Maximum (LGM). This means that during periods of low sea-levels the amount of terrigenous material would have been greater than in periods of sea-level high stands. In fact, colour reflectance of the entire core (following the technique applied by Lourens, 2004, to deep-sea cores from the Mediterranean Sea) carried out on the ship soon after the opening of the cores clearly supported this observation. For additional information, refer to the Supplemental material (Figure S5).