Relative Paleointensity (RPI) and Age Control in Antarctic Marine Drift Sediments

GSTDTAP

项目编号	1542579
	Relative Paleointensity (RPI) and Age Control in Antarctic Marine Drift Sediments
	James Channell
主持机构	University of Florida
项目开始年	2016
	2016-05-01
项目结束日期	2018-04-30
资助机构	US-NSF
项目类别	Standard Grant
项目经费	131287(USD)
国家	美国
语种	英语
英文摘要	During the last interglacial (LIG) warm interval, ~125 thousand years ago, mean global temperature is estimated to have been only very slightly elevated (by perhaps 1-2 °C), relative to today. At that same time, global sea level was elevated by ~6-9 m, relative to present, according to studies of exposed corals in Australia, the Seychelles, and the Caribbean. Such high sea level today would displace up to 20% of the US population. It is estimated that Greenland glacial melting could have accounted for ~2 m of sea-level rise, thermal expansion of the oceans and melting of mountain glaciers could account for ~0.5 m each, but Antarctica must account for the bulk of it. Where did the melting occur? It has been speculated that the one particular part of Antarctica (the West Antarctic Ice Sheet, WAIS) was the site of the inferred melting. The marine sediments that have accumulated off-shore West Antarctica should provide evidence of this melting, but the lack of robust age control in Antarctic marine sediments has stymied their interpretation in terms of past instability of WAIS. This proposal tests a relatively new method, involving the recording of the past geomagnetic field by the sediments themselves, that can provide age models for the Antarctic marine sediments, contribute their interpretation in terms of instability of WAIS over the last few climate cycles, and hence contribute to our current climate/sea level dilemma. Over the last 20 years, relative (geomagnetic) paleointensity (RPI) proxies have been combined with oxygen isotope data in Quaternary sediments in the North Atlantic with the objective of implementing RPI as a high-resolution stratigraphic correlation tool. The relatively rapid rate of change of geomagnetic field intensity (currently about 5% per century), and the fact that sediments with sedimentation rates <~50 cm/kyr are likely to record only the main axial dipole component of the field, means that RPI can be expected to provide a high-resolution global correlation tool. There are now several examples of tandem correlations involving RPI and oxygen isotope data over the last few Myrs, implemented through automated matching protocols such as 'Match'. The results have led to the generation of temporally calibrated reference stacks for RPI (such as PISO) that can be used, in conjunction with oxygen isotope data, to provide improvements in the resolution of Quaternary stratigraphies. This proposal is to test the use of RPI as a stratigraphic tool in marine sediment drifts off the Antarctic Peninsula and in the Bellingshausen Sea, using seven piston cores recovered in early 2015 during cruise JR298 of the RRS James Clark Ross. The west Antarctic region provides an important test of the stratigraphic role of relative paleointensity (RPI) proxies because the sedimentation history of Antarctic sediment drifts is a key to interpreting their sedimentation history in terms of instability of the West Antarctic Ice Sheet (WAIS) and Antarctic Peninsula Ice Sheet (APIS). The paucity of foraminiferal carbonate at high southerly latitudes means that age models in sediments from the region cannot rely on oxygen isotope data. Age models in these Antarctic drifts have relied on the association of high biogenic siliceous/carbonate percentage (as well as proxies for high biogenic content from magnetic susceptibility, wet bulk density and biogenic Ba content) with interglacial marine isotopic stages. These methodologies are not ideal because they have low resolution and impose interpretations on the sediment record. For these reasons, we seek new methods for determining age in these drift sediment using RPI to interpret sedimentation rates, XRF core scanning data, and ice-rafting debris (IRD) proxies, in terms of instability of WAIS and APIS. This project will be assisted by an undergraduate researcher.
来源学科分类	Geosciences - Polar Programs
文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/69439
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	James Channell.Relative Paleointensity (RPI) and Age Control in Antarctic Marine Drift Sediments.2016.