Ezer Tal

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  • Article
    Improving oceanic overflow representation in climate models : the Gravity Current Entrainment Climate Process Team
    (American Meteorological Society, 2009-05) Legg, Sonya ; Ezer, Tal ; Jackson, Laura ; Briegleb, Bruce P. ; Danabasoglu, Gokhan ; Large, William G. ; Wu, Wanli ; Chang, Yeon ; Ozgokmen, Tamay M. ; Peters, Hartmut ; Xu, Xiaobiao ; Chassignet, Eric P. ; Gordon, Arnold L. ; Griffies, Stephen M. ; Hallberg, Robert ; Price, James F. ; Riemenschneider, Ulrike ; Yang, Jiayan
    Oceanic overflows are bottom-trapped density currents originating in semienclosed basins, such as the Nordic seas, or on continental shelves, such as the Antarctic shelf. Overflows are the source of most of the abyssal waters, and therefore play an important role in the large-scale ocean circulation, forming a component of the sinking branch of the thermohaline circulation. As they descend the continental slope, overflows mix vigorously with the surrounding oceanic waters, changing their density and transport significantly. These mixing processes occur on spatial scales well below the resolution of ocean climate models, with the result that deep waters and deep western boundary currents are simulated poorly. The Gravity Current Entrainment Climate Process Team was established by the U.S. Climate Variability and Prediction (CLIVAR) Program to accelerate the development and implementation of improved representations of overflows within large-scale climate models, bringing together climate model developers with those conducting observational, numerical, and laboratory process studies of overflows. Here, the organization of the Climate Process Team is described, and a few of the successes and lessons learned during this collaboration are highlighted, with some emphasis on the well-observed Mediterranean overflow. The Climate Process Team has developed several different overflow parameterizations, which are examined in a hierarchy of ocean models, from comparatively well-resolved regional models to the largest-scale global climate models.
  • Article
    Towards comprehensive observing and modeling systems for monitoring and predicting regional to coastal sea level
    (Frontiers Media, 2019-07-25) Ponte, Rui M. ; Carson, Mark ; Cirano, Mauro ; Domingues, Catia M. ; Jevrejeva, Svetlana ; Marcos, Marta ; Mitchum, Gary ; van de Wal, Roderik S.W. ; Woodworth, Philip L. ; Ablain, Michaël ; Ardhuin, Fabrice ; Ballu, Valerie ; Becker, Mélanie ; Benveniste, Jérôme ; Birol, Florence ; Bradshaw, Elizabeth ; Cazenave, Anny ; De Mey-Frémaux, Pierre ; Durand, Fabien ; Ezer, Tal ; Fu, Lee-Lueng ; Fukumori, Ichiro ; Gordon, Kathy ; Gravelle, Médéric ; Griffies, Stephen M. ; Han, Weiqing ; Hibbert, Angela ; Hughes, Chris W. ; Idier, Deborah ; Kourafalou, Vassiliki H. ; Little, Christopher M. ; Matthews, Andrew ; Melet, Angelique ; Merrifield, Mark ; Meyssignac, Benoit ; Minobe, Shoshiro ; Penduff, Thierry ; Picot, Nicolas ; Piecuch, Christopher G. ; Ray, Richard D. ; Rickards, Lesley ; Santamaría-Gómez, Alvaro ; Stammer, Detlef ; Staneva, Joanna ; Testut, Laurent ; Thompson, Keith ; Thompson, Philip ; Vignudelli, Stefano ; Williams, Joanne ; Williams, Simon D. P. ; Wöppelmann, Guy ; Zanna, Laure ; Zhang, Xuebin
    A major challenge for managing impacts and implementing effective mitigation measures and adaptation strategies for coastal zones affected by future sea level (SL) rise is our limited capacity to predict SL change at the coast on relevant spatial and temporal scales. Predicting coastal SL requires the ability to monitor and simulate a multitude of physical processes affecting SL, from local effects of wind waves and river runoff to remote influences of the large-scale ocean circulation on the coast. Here we assess our current understanding of the causes of coastal SL variability on monthly to multi-decadal timescales, including geodetic, oceanographic and atmospheric aspects of the problem, and review available observing systems informing on coastal SL. We also review the ability of existing models and data assimilation systems to estimate coastal SL variations and of atmosphere-ocean global coupled models and related regional downscaling efforts to project future SL changes. We discuss (1) observational gaps and uncertainties, and priorities for the development of an optimal and integrated coastal SL observing system, (2) strategies for advancing model capabilities in forecasting short-term processes and projecting long-term changes affecting coastal SL, and (3) possible future developments of sea level services enabling better connection of scientists and user communities and facilitating assessment and decision making for adaptation to future coastal SL change.