A 1.5-million-year record of orbital and millennial climate variability in the North Atlantic
David A HodellSimon J CrowhurstLucas Joost LourensVasiliki MargariJohn NicolsonJames RolfeLuke C SkinnerNicola C. ThomasPolychronis C. TzedakisMaryline J. VautraversE. W. Wolff
28
Citation
172
Reference
10
Related Paper
Citation Trend
Abstract:
Abstract. Climate during the last glacial period was marked by abrupt instability on millennial timescales that included large swings of temperature in and around Greenland (Daansgard–Oeschger events) and smaller, more gradual changes in Antarctica (AIM events). Less is known about the existence and nature of similar variability during older glacial periods, especially during the early Pleistocene when glacial cycles were dominantly occurring at 41 kyr intervals compared to the much longer and deeper glaciations of the more recent period. Here, we report a continuous millennially resolved record of stable isotopes of planktic and benthic foraminifera at IODP Site U1385 (the “Shackleton Site”) from the southwestern Iberian margin for the last 1.5 million years, which includes the Middle Pleistocene Transition (MPT). Our results demonstrate that millennial climate variability (MCV) was a persistent feature of glacial climate, both before and after the MPT. Prior to 1.2 Ma in the early Pleistocene, the amplitude of MCV was modulated by the 41 kyr obliquity cycle and increased when axial tilt dropped below 23.5∘ and benthic δ18O exceeded ∼3.8 ‰ (corrected to Uvigerina), indicating a threshold response to orbital forcing. Afterwards, MCV became focused mainly on the transitions into and out of glacial states (i.e. inceptions and terminations) and during times of intermediate ice volume. After 1.2 Ma, obliquity continued to play a role in modulating the amplitude of MCV, especially during times of glacial inceptions, which are always associated with declining obliquity. A non-linear role for obliquity is also indicated by the appearance of multiples (82, 123 kyr) and combination tones (28 kyr) of the 41 kyr cycle. Near the end of the MPT (∼0.65 Ma), obliquity modulation of MCV amplitude wanes as quasi-periodic 100 kyr and precession power increase, coinciding with the growth of oversized ice sheets on North America and the appearance of Heinrich layers in North Atlantic sediments. Whereas the planktic δ18O of Site U1385 shows a strong resemblance to Greenland temperature and atmospheric methane (i.e. Northern Hemisphere climate), millennial changes in benthic δ18O closely follow the temperature history of Antarctica for the past 800 kyr. The phasing of millennial planktic and benthic δ18O variation is similar to that observed for MIS 3 throughout much of the record, which has been suggested to mimic the signature of the bipolar seesaw – i.e. an interhemispheric asymmetry between the timing of cooling in Antarctica and warming in Greenland. The Iberian margin isotopic record suggests that bipolar asymmetry was a robust feature of interhemispheric glacial climate variations for at least the past 1.5 Ma despite changing glacial boundary conditions. A strong correlation exists between millennial increases in planktic δ18O (cooling) and decreases in benthic δ13C, indicating that millennial variations in North Atlantic surface temperature are mirrored by changes in deep-water circulation and remineralization of carbon in the abyssal ocean. We find strong evidence that climate variability on millennial and orbital scales is coupled across different timescales and interacts in both directions, which may be important for linking internal climate dynamics and external astronomical forcing.Keywords:
Orbital forcing
Paleoclimatology
Early Pleistocene
Last Glacial Maximum
Cite
Citations (11)
Cite
Citations (20)
A general introduction to the Pleistocene with an emphasis on herpetological remains was presented in the companion volume Pleistocene Amphibians and Reptiles in North America (Holman, 1995c). For a general introduction to the Pleistocene that gives much attention to Britain and Europe, the reader is referred to Sutcliffe (1985). A detailed account of Pleistocene mammals in Britain is given by Stuart (1982), and a general account of Pleistocene mammals in Europe is given by Kurten (1968). The present chapter deals mainly with chronological divisions of the Pleistocene in Britain and Europe. Early geologists recognized that glacial deposits and land forms existed far south of existing glaciated areas, and they correctly reasoned that these features indicated not only the presence of ice sheets but the onset of cold climates, as well. As these features were mapped and stratigraphic studies were made, it was found that some sections contained weathered zones of organic soils and plant remains between layers of glacially derived sediments. It was suggested that these organic zones represented nonglacial environments and that ice sheets must have advanced and retreated several times. In Europe, before studies of deep sea sediments were made, Pleistocene chronological events were determined on the basis of piecemeal evidence from terrestrial sediments. The earliest widely accepted chronology of climatic Pleistocene intervals was the classic fourfold subdivision of Pleistocene glacial events in the Alps by Penck and Bruckner (1909). These glacial stage names, from oldest to youngest, are Gu'nz glacial, Mindcl glacial, Riss glacial, and Wiirm glacial. Between the glacial stages, intcrglacial stages were designated by compound names based on the underlying and overlying glacial stages (e.g., The Gunz-Mindel intcrglacial stage lies between the Giinz and Mindel glacial stages). These Alpine glacial stages have been widely used, and one still finds references to them (especially the younger stages) in the recent literature (e.g., Fritz, 1995).
Early Pleistocene
Cite
Citations (0)
Abstract Geomorphological evigernce indicates that Mount Badda, Ethiopia, had a Pleistocene ice cap of at least 140 km 2 . Altituger of the snow line was probably about 4 000 m, only 350 m below the summit, suggesting that glaciation occurred during the Würm glacial maximum.
Summit
Cite
Citations (37)
The criticisms and views expressed in the recently circulated preliminary report of the Pleistocene committee of the American Commission on Stratigraphic Nomenclature on the present stratigraphic system of classification of the Quaternary suggest some lack of familiarity with the classic area of the Middle West. The multiple classification that the committee recommends, excellent as it may be for the older rocks, is not compatible with the nature of the glacial Pleistocene. The classification for the older rocks is the natural result of acquiring an understanding of them, just as the present classification of the glacial Pleistocene has evolved from decades of investigation. The classic area of the glacial Pleistocene comprises all of the type areas for the known glacial and interglacial stages of North America. So influential were the climates on most geologic processes, even in the depths of the ocean, that correlations with the glacial and interglacial stages of the Pleistocene are sought from all quarters. It is therefore important that the system of stratigraphic classification for the glacial Pleistocene shall be one that is naturally adapted to it rather than one that applies to marine strata. The non-glacial Pleistocene, however, may well be susceptible to the latter.
Early Pleistocene
Viewpoints
Cite
Citations (11)
Wisconsin glaciation
Eemian
Early Pleistocene
Cite
Citations (1)
Yulong Mountains (27°10′～27°40′N, 100°9′～100°20′E), situated in the north of Lijiang County, Yunnan Province and the southeast margin of the Tibetan Plateau, are the southernmost mountains with glaciers both in China and Eurasia Along their east, northeast and west feet, there is a series of relics of the Pleistocene glaciation Studying these glaciation relics and reconstructing their history of evolution have not only an important scientific implication for understanding the changes of glaciation, climate and environment and for discussing the uplift of the Hengduan Mountains and the Tibetan Plateau, as well as the development of the Jinsha River valley and the formation and development of Asian monsoon, but also major practical values for developing and protecting the tremendous resources of hydraulics and tourism in this area The authors survey, research and map the Pleistocene glacial deposits along the eastern foot of the Yulong Mountains based on the topographic map with the scale of 1∶10 000 and air-photographs, determining ESR dates of samples of calcareous cements from the glacial and fluvioglacial deposits as well as the calcareous glacio-lacustrine deposits, dividing them into four glaciations, i e the early Middle Pleistocene Yulong Glaciation (0 7～0 6 Ma BP), the middle Middle Pleistocene Ganhaizi Glaciation (0 53～0 45 Ma BP), the late Middle Pleistocene Lijiang Glaciation (0 31～0 13 Ma BP) and the Late Pleistocene Dali Glaciation, and correlating them with the glaciations on the Tibetan Plateau Results of study show that the Yulong Mountains area was a part of the united peneplain from the Tibetan Plateau to the Yunnan-Guizhou Plateau, 500～1 000 m a s l , during the Miocene In the Pliocene and the Early Pleistocene, the Yulong Mountains uplifted and the Lijiang Basin, Daju Basin, Longpan Valley and other basins subsided due to the fault activities In the early Middle Pleistocene, the Yulong Mountains had uplifted over the snowline, and giant piedmont glaciers of the Yulong Glaciation, the largest glaciation in this area, occurred at their east, west and northeast feet The glaciers in the Ganhaizi Glaciation were also piedmont ones, but muchsmaller than the former During the following grand interglacial, the Longpan Valley and the Daju Basin became two lakes, and then cut by the modern Jinsha River In the late Middle Pleistocene and the Late Pleistocene, the larger-scale valley glaciers of the Lijiang and Dali Glaciations developed in the tributaries of the Jinsha River
Early Pleistocene
Cite
Citations (7)
Stratigraphic sections and radiocarbon dates serve as a basis for defining four substages in the late Pleistocene Itkillik glaciation which are correlated with the four substages of the Wisconsin glaciation of central North America. Three post-Itkillik advances, restricted to the highest parts of the range, are correlated with post-hypsithermal advances elsewhere in the North American Cordillera.
Chronology
Cite
Citations (28)
Early Pleistocene
Cite
Citations (195)