Dependence of Antarctic sea-ice extent on mesoscale ocean variability in the Southern Ocean

南极海冰范围对南大洋中尺度海洋变化的依赖性

• 批准号: 1357522
• 负责人: Laurence Padman
• 金额: $ 46.44万
• 依托单位: Earth and Space Research
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-04-01 至 2019-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1357522&HistoricalAwards=false
• 关键词: Dependence; Antarctic; sea; ice; extent

Overview: Sea ice extent around Antarctica has slowly increased over the satellite era (1979-present), against the general decline of other global cryosphere components and contrary to modern negative sea ice extent trends in global coupled climate models (CCMs). Previous hypotheses have focused on large-scale mechanisms that impact the sea ice mass balance: changes in wind stress fields due to stratospheric ozone depletion; a more energetic Southern Ocean hydrologic cycle; increased downwelling long wave radiation; and enhanced freshwater production under ice shelves. An additional hypothesis will be tested: Mesoscale ocean processes that are not resolved in CCMs play a significant role in controlling ice edge position and sea-ice characteristics in the marginal ice zone and that inter-annual variability and trends in ocean mesoscale activity can drive changes in sea ice extent that are not closely correlated with the annual-averaged Southern Ocean state such as position of Antarctic Circumpolar Current fronts.Intellectual Merit: Daily satellite-derived sea-ice concentration fields will be analyzed to determine the effect of ocean mesoscale variability on sea-ice edge characteristics that influence true and satellite-measured sea-ice extent. Statistics will include the increase in ice-edge length due to mesoscale processes as a measure of increased exposure of the Marginal Ice Zone to "open-ocean" processes. Sea ice extent derived from different gridded datasets of sea-ice concentration will be compared to determine whether inter-annual variability and trends in sea ice extent are sensitive to measurement methodology and spatial resolution. If justified by prior work, near-contemporaneous Envisat ASAR high-resolution radar images will then be compared with sea-ice concentration fields from AMSR-E. A database of tracked eddies will also be analyzed to determine whether eddies generated by Antarctic Circumpolar Current frontal instabilities and interactions with topography contribute to ice-edge variability. These analyses will be performed on circum-Antarctic and regional scales, at annual resolution to resolve inter-annual variability and trends.The output from an eddy-permitting three-dimensional regional ocean model with coupled sea ice or a data-constrained ocean state model (Southern Ocean State Estimate) will be analyzed to investigate how well these models represent the ocean mesoscale contribution to ice-edge perturbations. The investigators will also develop their own idealized models of ocean/ice/atmosphere interactions at the ice edge to investigate mechanisms for generation of ice-edge fronts whose instabilities may be significant contributors to the ice-edge mesoscale field.Broader Impacts: This study will elucidate the mechanisms coupling the highly energetic Southern Ocean mesoscale field with sea ice. Antarctic sea ice has a profound effect on albedo, ocean/atmosphere heat and moisture fluxes and gas exchange, and so is an important component of the global coupled climate system. The concurrent analyses of existing data and eddy-permitting ocean/sea-ice models will inform interpretation of sea-ice variability in modern CCMs, and so identify critical developments needed to improve their representation of sea ice. Careful examination of the marginal ice zone will help inform the interpretation of satellite retrievals of ice-edge position. The investigators will continue their participation in local outreach activities including presentations at Pacific Science Center (Seattle) and the Robinson Center for Young Scholars at the University of Washington, public talks in Oregon and frequent contributions on Climate Science to the Corvallis newspaper Opinion Page, development of a project web page targeted at a general audience, and updating their outreach web site including polar photo server.

概述：南极周围的海冰范围在卫星时代（1979年至今）逐渐增加，反对其他全球冰冻圈成分的总体下降，并且与全球耦合气候模型（CCMS）中现代的负海冰范围趋势相反。先前的假设集中在影响海冰质量平衡的大规模机制上：由于平流层臭氧耗竭引起的风应力场的变化；南方海洋水文周期更具活力；下降的长波辐射增加；并在冰架下增强了淡水生产。将测试一个额外的假设：在CCMS中无法解决的中尺度海洋过程在控制冰边缘位置和边缘冰区的海上特征以及海洋中尺度活动的年度可变性和趋势中可以推动海冰的变化与每日循环的变化相关：将分析卫星衍生的海冰浓度场，以确定海洋中尺度变异性对影响真实和卫星测量海冰范围的海冰边缘特征的影响。统计数据将包括由于中尺度过程而导致的冰边长度的增加，以衡量边际冰区域对“开放海洋”过程的暴露。将比较从海冰浓度的不同网格数据集中得出的海冰范围，以确定海冰际变异性和海冰范围的趋势是否对测量方法和空间分辨率敏感。如果通过先前的工作证明是合理的，那么将与AMSR-E的Sea-Ice浓度场进行比较，将近距离的ASAR ASAR高分辨率雷达图像进行比较。还将分析轨道涡流的数据库，以确定南极极性电流额叶额不稳定性产生的涡流以及与地形的相互作用是否有助于冰边变异性。 These analyses will be performed on circum-Antarctic and regional scales, at annual resolution to resolve inter-annual variability and trends.The output from an eddy-permitting three-dimensional regional ocean model with coupled sea ice or a data-constrained ocean state model (Southern Ocean State Estimate) will be analyzed to investigate how well these models represent the ocean mesoscale contribution to ice-edge perturbations.研究人员还将开发自己的理想化模型在冰边缘的海洋/冰/大气相互作用，以研究生成冰边阵线的机制，其不稳定性可能是冰边缘中尺度领域的重要贡献者。Boader的影响：这项研究将阐明与高度有力的南部海洋苏西莱海洋冰相结合的机制。南极海冰对反照率，海洋/大气热和水分通量和气体交换具有深远的影响，因此，全球耦合气候系统的重要组成部分也是如此。对现有数据的并发分析和涡流的海洋/海冰模型将为现代CCM中的海冰变异性解释提供信息，因此确定了改善其海冰代表所需的关键发展。仔细检查边缘冰区将有助于告知对冰边卫星检索的解释。调查人员将继续参加当地的外展活动，包括在太平洋科学中心（西雅图）和华盛顿大学的鲁滨逊年轻学者中心的演讲，俄勒冈州的公共谈判，以及对Corvallis报纸意见页面的气候科学频繁贡献，开发针对普通受众的项目网页，并更新其外展网站，并更新包括Polor Photophopol Photophopher Photo Plarther的图片服务器。