Searching the proposed Northern Source of the MPT start of the 100-ka climate cyclicity

点击翻译按钮获取中文摘要

The Mid-Pleistocene-Transition (MPT) is an enigmatic climate period during which, without substantial changes in astronomical forcing, swing from ∼41-ka to 100-ka climate cyclicity occurred. Recent findings indicate changes in Northern Hemispheric glacial erosion/weathering of Regolith preceding the cyclicity shift and a massive reduction of the Atlantic Meridiornal Overturning circulation (AMOC). Furthermore, the rapid expansion northern hemisphere ice-sheets was accompanied by phases of pronounced subsurface heat accumulation at up to 57°N. The required extra heat is thought to reflect increased outflow of the Mediterranean Sea (MOW) or strengthening of the North Atlantic current (NAC). All mechanisms is in common that tipping points must be crossed, which are difficult to determine regarding the timing and mechanisms. None of the observations and models, however, predict a singular transition. Recent studies of framework forming cold-water corals in the eastern North Atlantic follow similar climate influence and physical processes. The occurrence of corals has been linked to the thermal history and productivity displacements of the polar and subtropical fronts. A significant role of MOW and NAC on coral growth and expansion has been invoked. Challenger Mound in the Porcupine Seabight evolved across the MPT and thus is the only site permitting to test mechanisms of climate cooling, overturning changes (latitudinal heat fluxes), and regolith weathering coupled to marine records. Punctuated observations of discontinuous coral growth are unlikely to provide unique evidence of the northern hemisphere “cold-threshold” into the 100-ka cycles, But, thanks to recent advance towards 234U/238U and U/Pb dating, coral responses to climate change and water mass configuration changes may be precisely dated. Moreover, through a comprehensive study of corals (IODP U1317 - Challenger Mound) and northern hemisphere sediments from various sites (ODP 982, IODP U1304, and IODP U1388/1386) we intent to test the hypothesis of enhanced Regolith weathering, climate cooling, and MOW or NAC advances across the bi-furcation into new global climate states. To achieve this goal the project has two data streams: (1) More precise timing of events through innovation of coral dating and revisiting mound evolution and (2) Reconstruction of the thermal history and water mass provenance and weathering patterns using geochemical tracers of temperature (Li/Mg) and radiogenic Nd. Through a synthesis of all new findings and previous reviews on the ice-sheet dynamic and thermal structure of the northeast Atlantic we will build a new conceptual model of threshold crossing and its possible northern hemisphere source region. The project should be conducted by an early stage postdoctoral researcher and build on the combined forces of expert teams at Heidelberg University and University Frankfurt providing a unique research environment and infra-structure.