Although the dramatic climate disruptions of the last glacial period have received considerable attention, relatively little has been directed toward climate variability in the Holocene (11,500 cal yr B.P. to the present). Examination of ?50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000"8000, 6000"5000, 4200"3800, 3500"2500, 1200"1000, and 600"150 cal yr B.P. Most of the climate change events in these globally distributed records are characterized by polar cooling, tropical aridity, and major atmospheric circulation changes, although in the most recent interval (600"150 cal yr B.P.), polar cooling was accompanied by increased moisture in some parts of the tropics. Several intervals coincide with major disruptions of civilization, illustrating the human significance of Holocene climate variability.

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A clean hot-water drill was used to gain access to Subglacial Lake Whillans (SLW) in late January 2013 as part of the Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project. Over 3 days, we deployed an array of scientific tools through the SLW borehole: a downhole camera, a conductivity-temperature-depth (CTD) probe, a Niskin water sampler, an in situ filtration unit, three different sediment corers, a geothermal probe and a geophysical sensor string. Our observations confirm the existence of a subglacial water reservoir whose presence was previously inferred from satellite altimetry and surface geophysics. Subglacial water is about two orders of magnitude less saline than sea water (0.37-0.41 psu vs 35 psu) and two orders of magnitude more saline than pure drill meltwater (<0.002 psu). It reaches a minimum temperature of -0.558C, consistent with depression of the freezing point by 7.019 MPa of water pressure. Subglacial water was turbid and remained turbid following filtration through 0.45 mm filters. The recovered sediment cores, which sampled down to 0.8 m below the lake bottom, contained a macroscopically structureless diamicton with shear strength between 2 and 6 kPa. Our main operational recommendation for future subglacial access through water-filled boreholes is to supply enough heat to the top of the borehole to keep it from freezing.

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Marine sediment cores are the fundamental data source for information on seabed character, depositional history and environmental change. They provide raw data for a wide range of research including studies of global climate change, palaeoceanography, slope stability, oil exploration, pollution assessment and control, and sea-floor surveys for laying cables, pipelines and siting of sea-floor structures. During the last three decades, a varied suite of new technologies have been developed to analyse cores, often non-destructively, to produce high-quality, closely spaced, co-located downcore measurements, characterizing sediment physical properties, geochemistry and composition in unprecedented detail. Distributions of a variety of palaeoenvironmentally significant proxies can now be logged at decadal and, in some cases, even annual or subannual scales, allowing detailed insights into the history of climate and associated environmental change. These advances have had a profound effect on many aspects of the Earth Sciences, particularly palaeoceanography. In this paper, we review recent advances in analytical and logging technology, and their application to the analysis of sediment cores. Developments in providing access to core data and associated datasets, and data-mining technology, in order to integrate and interpret new and legacy datasets within the wider context of sea-floor studies, are also discussed. Despite the great advances in this field, however, challenges remain, particularly in the development of standard measurement and calibration methodologies and in the development of data analysis methods. New data visualization tools and techniques need to be developed to optimize the interpretation process and maximize scientific value. Amplified collaboration environments and tools are needed in order to capitalize on our analysis and interpretation capability of large, multi-parameter datasets. Sophisticated, yet simple to use, searchable Internet databases, with universal access and secure long-term funding, and data products resulting in user-defined data-mining query and display, so far pioneered in the USA and Australia, provide robust models for efficient and effective core data stewardship.