End Of Last Glacial Maximum Research Articles

Latest Pleistocene glacial and climate history of the Wasatch Range, Utah

The geologic record of mountain glaciation is one of the most sensitive archives of terrestrial climate change during the late Quaternary Period. Pleistocene glacial deposits are exceptionally well preserved in the Great Basin of North America where they are found in close proximity to shoreline deposits of coeval paleo-lakes, representing a unique opportunity to investigate paleoclimate change using both hydrologic systems. Mountain glaciers advanced across much of the Wasatch Range, Utah during the same general time interval when Lake Bonneville expanded in the adjacent Bonneville Basin. Here we present a range-wide Latest Pleistocene glacial history for the Wasatch Range based on 22 new and 41 recalculated cosmogenic 10Be surface exposure ages, and reconstruct glaciers and climate for the Last Glacial Maximum (LGM) and Lateglacial periods. Our results indicate three distinct, range-wide phases of glaciation in the Wasatch including the Pinedale 1 (ca. 21–20 ka), Pinedale 2 (ca. 17.5 ka) and Pinedale 3 (ca. 15 ka). Our modeling results indicate that the Pinedale 1 advance, near the end of the global LGM, was primarily driven by decreased annual temperatures with little to no change in precipitation as compared to modern. Wasatch glaciers appear to have reoccupied near maximum positions after the end of the LGM during the Pinedale 2, responding to increased precipitation in concert with rising lake levels across Western North America, and then retreated from ice-distal positions near ca. 17.5 ka. Wasatch glaciers occupied recessional positions at approximately half their maximum lengths during Pinedale 3 until ca. 15 ka, followed by rapid (i.e. several millennia) deglaciation. Our glacial chronologies establish that Wasatch glaciers responded synchronously across the range to global and regional climate forcings during the Latest Pleistocene. The new Wasatch glacial chronology, combined with global glacial chronologies and paleoclimate proxies from Western North America, suggest glacier change was driven by a combination of long-term global temperature forcing as well as regional to local modifications in precipitation.

Sympatric and allopatric niche shift of endemic Gypsophila (Caryophyllaceae) taxa in the Iberian Peninsula.

Several species of the Gypsophila genus are endemic to the Iberian Peninsula, including gypsophytes of particular ecological, evolutionary and biochemical interest, and taxa that have undergone both sympatric and allopatric genetic differentiation. The niche shift among these taxa has been assessed using ecological niche modelling and ordination techniques, adopting a niche overlap approach to compare the similarity and equivalency of the ecological niches. We used the Maximum Entropy method to study the potential distribution of these taxa in different eras: the Last Glacial Maximum (LGM), the Mid Holocene and the current conditions. We present evidence of niche shift during the speciation of G. bermejoi, with a strong niche overlap between the parental taxa (G. struthium subsp. struthium and G. tomentosa), yet both overlap much more weakly with the hybrid species. This phenomenon may be explained by genetic and epigenetic interactions, and it has been described in other species. We also studied the sister subspecies G. struthium subsp. struthium and G. struthium subsp. hispanica, with mostly allopatric distributions and with the Iberian System mountain range acting as a geographical barrier. The Iberian System and other mountain ranges may have favored differences in the climatic conditions on either side of the mountain range, which is consistent with an incipient process of bioclimatic ecological speciation. These results seem to indicate that niche shift can occur over very different timespans. In the case of G. bermejoi, speciation may have produced significant niche shifting in one or two generations due to its alloploid nature. By contrast, G. struthium subsp. struthium and G. struthium subsp. hispanica seem to have undergone a more gradual process of allopatric genetic differentiation driven by bioclimatic factors. Both these processes are relatively recent and they will have been strongly influenced by the climate change at the end of LGM.

Glacial to Holocene changes in sea surface temperature and seawater δ18O in the northern Indian Ocean

Sea surface temperature (SST) and seawater δ18Osw records were generated from sediment cores located in the southern Bay of Bengal (SBOB) and the northeastern Arabian Sea (NEAS) to understand glacial to Holocene changes in the hydrography of these regions. This was accomplished through the use of paired δ18O and Mg/Ca measurements in planktic foraminifera (Globigerinoides ruber) from two sediment cores; SK157-14 in the SBOB (lat. 5°11′N; long. 90°05′E; water-depth 3306m) and SK148-21 in the NEAS (lat. 21°29′N, long. 67°01′E; water-depth 1900m). The results suggest significant changes in SST and δ18Osw since last glacial period. The glacial SSTs in the SBOB and the NEAS were lower by ~2–2.5°C relative to the Holocene. The deglacial period in both cores is characterized by significant variations in SSTs and seawater δ18Osw. The Dansgaard-Oeschger (DO) cycles and Heinrich events are strongly expressed in SST and δ18Osw records of the SBOB core. These records support a strong control of atmospheric-oceanic changes in the northern high latitude on thermal state of the SBOB. The SST time series in both these regions indicates a sudden and abrupt increase in temperature at the end of last glacial maximum. The SST time series in the NEAS core SK 148-21 reveals an intensification of the northeast monsoon during the last glacial maximum.