A continuous record of Holocene eolian activity in West Greenland     

Nico W. Willemse  Eduard A. Koster  Babette Hoogakker  Frank G. M. van Tatenhove   《Quaternary Research》2003,59(3):322-334

Eolian landforms are widespread alongside proglacial valley-sandurs in West Greenland and comprise low-relief sand sheets, climbing dunes, and upland loess. Sedimentary facies mainly reflect distance to outwash-source zones and the influence of vegetation cover. The sediments show stratification types typical for poorly to moderately vegetated sand-sheets, alternately laminated silt/peat sequences, and unstratified loess. Twenty-five accelerator mass spectrometry ¹⁴C dates provide the basis for the chronostratigraphy of the inland eolian deposits. ¹⁴C dates from interstratified sand-sheets suggest that the bulk of eolian sands were deposited prior to 3400 cal yr B.P. and after 550 cal yr B.P. This two-phase formation for the inland dunes most likely reflects local changes in proglacial floodplain development and meltwater rerouting associated with a significant recession of the Greenland ice sheet during the mid Holocene climate optimum. Subsequent floodplain regeneration and renewed sand-sheet formation after 550 cal yr B.P. followed when the ice margin readvanced to its present position. In contrast, atmospheric deposition of regionally derived silt in upland peat mires has been continuous since at least 4750 cal yr B.P. Silt influx data demonstrate a strongly episodic history of the intensity of eolian activity over the past five millennia, which tentatively reflects alternating periods of (winter) aridity associated with the variable incursion of maritime air masses over the interior ice-free areas of West Greenland.  相似文献   

The distribution of strontium between coexisting silicate and carbonate liquids at elevated pressures and temperatures     

A.F.Koster van Groos 《Geochimica et cosmochimica acta》1975,39(1):27-34

Strontium is characteristically enriched in carbonatites and associated igneous rocks. Experiments between 600 and 800°C at 5 and 10 kb show that Sr fractionates strongly toward both liquid phases of a carbonate liquid-silicate liquid-solid assemblage, with the crystalline phases depleted in Sr. Considering that the alkalic igneous rocks associated with carbonatites are not significantly depleted in Sr compared with the carbonatites, it is concluded that these complexes are formed by a pair of immiscible magmas, rather than the carbonatites being late-stage fractionation products of the alkalic silicate magmas.  相似文献   

The role of soil moisture initialization in subseasonal and seasonal streamflow prediction – A case study in Sri Lanka     

Sarith P.P. Mahanama  Randal D. Koster  Rolf H. Reichle  Lareef Zubair 《Advances in water resources》2008

The two main contributors to streamflow predictability at subseasonal to seasonal timescales in tropical regions are: (i) the predictability of meteorologic (particularly precipitation) anomalies, and (ii) the land surface soil moisture state at the start of the forecast period. Meteorological predictions at subseasonal timescale are usually fraught with error and may not be dependable. The accurate initialization of soil moisture, as obtained through real-time land data analysis, may provide skill in subseasonal to seasonal streamflow prediction, even when the prediction skill for rainfall is small.  相似文献   

Seasonal variation of land–atmosphere coupling strength over the West African monsoon region in an atmospheric general circulation model     

Tomohito J. Yamada  Shinjiro Kanae  Taikan Oki  Randal D. Koster 《水文科学杂志》2013,58(6):1276-1286

Abstract

The seasonal variation of land–atmosphere coupling strength has been examined using an extended series of atmospheric general circulation model (AGCM) simulations. In the Western Sahel of Africa, strong coupling strength for precipitation is found in April and May, just prior to and at the beginning of the monsoon season. At this time, heat and water fluxes from the surface are strongly controlled by land conditions, and the unstable conditions in the lower level of the troposphere, as induced by local land state, allow the surface fluxes to influence the variability of convective precipitation—and thus the timing of monsoon onset.

Editor Z. W. Kundzewicz

Citation Yamada, T.J., Kanae, S., Oki, T., and Koster, R.D., 2013. Seasonal variation of land–atmosphere coupling strength over the West African monsoon region in an atmospheric general circulation model. Hydrological Sciences Journal, 58 (6), 1276–1286.  相似文献