Williams Michael J. M.

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Michael J. M.

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  • Article
    Delivering sustained, coordinated, and integrated observations of the Southern Ocean for global impact
    (Frontiers Media, 2019-08-08) Newman, Louise ; Heil, Petra ; Trebilco, Rowan ; Katsumata, Katsuro ; Constable, Andrew ; van Wijk, Esmee ; Assmann, Karen ; Beja, Joana ; Bricher, Phillippa ; Coleman, Richard ; Costa, Daniel P. ; Diggs, Stephen ; Farneti, Riccardo ; Fawcett, Sarah E. ; Gille, Sarah T. ; Hendry, Katharine R. ; Henley, Sian ; Hofmann, Eileen E. ; Maksym, Ted ; Mazloff, Matthew R. ; Meijers, Andrew J. S. ; Meredith, Michael M. ; Moreau, Sebastien ; Ozsoy, Burcu ; Robertson, Robin ; Schloss, Irene ; Schofield, Oscar M. E. ; Shi, Jiuxin ; Sikes, Elisabeth L. ; Smith, Inga J. ; Swart, Sebastiaan ; Wahlin, Anna ; Williams, Guy ; Williams, Michael J. M. ; Herraiz-Borreguero, Laura ; Kern, Stefan ; Lieser, Jan ; Massom, Robert A. ; Melbourne-Thomas, Jessica ; Miloslavich, Patricia ; Spreen, Gunnar
    The Southern Ocean is disproportionately important in its effect on the Earth system, impacting climatic, biogeochemical, and ecological systems, which makes recent observed changes to this system cause for global concern. The enhanced understanding and improvements in predictive skill needed for understanding and projecting future states of the Southern Ocean require sustained observations. Over the last decade, the Southern Ocean Observing System (SOOS) has established networks for enhancing regional coordination and research community groups to advance development of observing system capabilities. These networks support delivery of the SOOS 20-year vision, which is to develop a circumpolar system that ensures time series of key variables, and delivers the greatest impact from data to all key end-users. Although the Southern Ocean remains one of the least-observed ocean regions, enhanced international coordination and advances in autonomous platforms have resulted in progress toward sustained observations of this region. Since 2009, the Southern Ocean community has deployed over 5700 observational platforms south of 40°S. Large-scale, multi-year or sustained, multidisciplinary efforts have been supported and are now delivering observations of essential variables at space and time scales that enable assessment of changes being observed in Southern Ocean systems. The improved observational coverage, however, is predominantly for the open ocean, encompasses the summer, consists of primarily physical oceanographic variables, and covers surface to 2000 m. Significant gaps remain in observations of the ice-impacted ocean, the sea ice, depths >2000 m, the air-ocean-ice interface, biogeochemical and biological variables, and for seasons other than summer. Addressing these data gaps in a sustained way requires parallel advances in coordination networks, cyberinfrastructure and data management tools, observational platform and sensor technology, two-way platform interrogation and data-transmission technologies, modeling frameworks, intercalibration experiments, and development of internationally agreed sampling standards and requirements of key variables. This paper presents a community statement on the major scientific and observational progress of the last decade, and importantly, an assessment of key priorities for the coming decade, toward achieving the SOOS vision and delivering essential data to all end-users.
  • Article
    What lies beneath? Interdisciplinary outcomes of the ANDRILL Coulman High Project site surveys on the Ross Ice Shelf
    (The Oceanography Society, 2012-09) Rack, Frank R. ; Zook, Robert ; Levy, Richard H. ; Limeburner, Richard ; Stewart, Craig L. ; Williams, Michael J. M. ; Luyendyk, Bruce P. ; ANDRILL Coulman High Project Site Survey Team
    Extensive field operations were conducted on the northwestern Ross Ice Shelf in Antarctica from November 2010 through January 2011. A significant amount of equipment, supplies, and people safely traversed from McMurdo Station to establish a series of combined United States–New Zealand field camps at locations northeast of Ross Island. The ANDRILL (ANtarctic geological DRILLing) hot water drill system was used to melt multiple access holes through the ice shelf at each site to deploy a variety of sediment coring tools, cameras, and oceanographic instruments, as well as a remotely operated vehicle to characterize the ice shelf and sub-ice environment. These studies will contribute to future proposed geological drilling as part of the ANDRILL Coulman High Project.
  • Article
    Ocean variability contributing to basal melt rate near the ice front of Ross Ice Shelf, Antarctica
    (John Wiley & Sons, 2014-07-09) Arzeno, Isabella B. ; Beardsley, Robert C. ; Limeburner, Richard ; Owens, W. Brechner ; Padman, Laurie ; Springer, Scott R. ; Stewart, Craig L. ; Williams, Michael J. M.
    Basal melting of ice shelves is an important, but poorly understood, cause of Antarctic ice sheet mass loss and freshwater production. We use data from two moorings deployed through Ross Ice Shelf, ∼6 and ∼16 km south of the ice front east of Ross Island, and numerical models to show how the basal melting rate near the ice front depends on sub-ice-shelf ocean variability. The moorings measured water velocity, conductivity, and temperature for ∼2 months starting in late November 2010. About half of the current velocity variance was due to tides, predominantly diurnal components, with the remainder due to subtidal oscillations with periods of a few days. Subtidal variability was dominated by barotropic currents that were large until mid-December and significantly reduced afterward. Subtidal currents were correlated between moorings but uncorrelated with local winds, suggesting the presence of waves or eddies that may be associated with the abrupt change in water column thickness and strong hydrographic gradients at the ice front. Estimated melt rate was ∼1.2 ± 0.5 m a−1 at each site during the deployment period, consistent with measured trends in ice surface elevation from GPS time series. The models predicted similar annual-averaged melt rates with a strong annual cycle related to seasonal provision of warm water to the ice base. These results show that accurately modeling the high spatial and temporal ocean variability close to the ice-shelf front is critical to predicting time-dependent and mean values of meltwater production and ice-shelf thinning.