Incorporation of particulates into accreted ice above subglacial Vostok lake, Antarctica

• Published in: Annals of Glaciology
• Main Authors: Siegert, M. J., Royston-Bishop, G., Priscu, J. C., Tranter, M., Christner, B., Lee, V.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2005
• Subjects: Vostok Lake; Annals of Glaciology; Antarc*; Antarctica; ice core
• Online Access: http://hdl.handle.net/1842/2976; http://docserver.ingentaconnect.com/deliver/connect/igsoc/02603055/v40n1/s26.pdf?expires=1248364865&id=51323368&titleid=6496&accname=University+of+Edinburgh&checksum=DB28AC30CD1788D9E35F3D63EA1EDE2B; https://doi.org/10.3189/172756405781813555

The nature of microscopic particulates in meteoric and accreted ice from the Vostok (Antarctica) ice core is assessed in conjunction with existing ice-core data to investigate the mechanism by which particulates are incorporated into refrozen lake water. Melted ice samples from a range of icecore depths were filtered through 0.2 μm polycarbonate membranes, and secondary electron images were collected at ×500 magnification using a scanning electron microscope. Image analysis software was used to characterize the size and shape of particulates. Similar distributions of major-axis lengths, surface areas and shape factors (aspect ratio and compactness) for particulates in all accreted ice samples suggest that a single process may be responsible for incorporating the vast majority of particulates for all depths. Calculation of Stokes settling velocities for particulates of various sizes implies that 98% of particulates observed could 'float' to the ice water interface with upward water velocities of 0.0003 m s-1 where they could be incorporated by growing ice crystals, or by rising frazil ice crystals. The presence of particulates that are expected to sink in the water column (2%) and the uneven distribution of particulates in the ice core further implies that periodic perturbations to the lake's circulation, involving increased velocities, may have occurred in the past.