Characterising the Ice Shelf/Ocean Boundary Layer

描述冰架/海洋边界层的特征

• 批准号: NE/N009746/1
• 负责人: John Taylor
• 金额: $ 37.37万
• 依托单位: University of Cambridge
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2016
• 资助国家: 英国
• 起止时间: 2016 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FN009746%2F1
• 关键词: Characterising; Ice; Shelf; Ocean; Boundary

Global average sea level is rising by approximately 3 millimetres per year. Given the huge economic and societal impacts of this change, accurate forecasts of sea level are urgently needed to inform policymakers considering mitigation and adaptation strategies. Melting of the ice sheets of Antarctica and Greenland currently contributes about one third of sea level rise. The future of this melting is highly uncertain, and the worst-case scenario involves a substantial ice-sheet contribution to dangerous sea-level rise. The largest contribution to sea level rise from ice sheets occurs when the ocean melts the base of ice shelves (floating extensions of the grounded ice sheet). The melt rate of ice in seawater is determined by the transfer of heat and salt from the ocean towards the ice. Observations reveal a turbulent boundary layer in the ocean beneath ice shelves, where vigorous mixing is driven by the flow of rising meltwater, large-scale circulation in the ocean, and tides. Mixing of heat and salt in the boundary layer influences the ice melt rate, but the physical processes involved are poorly understood and will not be resolved in climate models for the foreseeable future. The proposed project will improve our understanding of the ice shelf/ocean boundary layer and develop improved representations of ice-shelf melting for use in climate models.To achieve these aims we will use a suite of numerical models and the latest observations. We will start with direct numerical simulations (DNS) to model a small box of ocean next to an ice shelf (~1 cubic metre) at ultra-high resolution (~1 millimetre). This will provide insight into the turbulence near the ice and its interaction with melting. We will then use large-eddy simulations (LES) to study a larger volume (~1 square kilometre in area by 100 metres height) at high resolution (~10 centimetres - 1 metre). This will resolve the largest turbulent motions in the whole boundary layer. Both models will be validated using recent observations obtained from mooring sites at the George VI and Larsen C ice shelves (Nicholls, NE/H009205/1). The model results will in turn help interpret and understand the observations.We will use these numerical models to devise and calibrate parameterisations for ice melting and vertical mixing for use in ocean climate models. We will add candidate parameterisations to a one-dimensional (vertical) model that incorporates many popular ocean mixing schemes, and test them directly against the DNS and LES results. We will begin with existing parameterisations and modify them as needed to match the high resolution models. The successful parameterisations will be implemented in the UK ocean model (NEMO) and shared with climate modelling groups (including the Met Office) to improve predictions of sea-level rise.

全球平均海平面每年增加约3毫米。鉴于这种变化的巨大经济和社会影响，迫切需要对海平面的准确预测，以告知考虑缓解和适应策略的决策者。目前，南极洲和格陵兰的冰盖融化目前贡献了海平面上升的三分之一。这种融化的未来是高度不确定的，最坏的情况涉及对危险海平面上升的巨大冰期贡献。当海洋融化冰架（接地冰盖的浮动延伸）时，会发生对海平面上升的最大贡献。海水中的冰速率取决于从海洋向冰的热和盐转移。观察结果揭示了冰架下的海洋中的湍流边界层，其中剧烈的混合是由上升的融化，海洋中的大规模循环和潮汐驱动的。边界层中的热和盐的混合会影响冰熔体的速率，但是涉及的物理过程知之甚少，并且在可预见的将来不会在气候模型中解决。拟议的项目将提高我们对冰架/海洋边界层的理解，并开发出改进的冰架融化以在气候模型中使用。为了实现这些目标，我们将使用一套数值模型和最新观察结果。我们将从直接的数值模拟（DNS）开始，以超高分辨率（〜1毫米）的冰架（〜1立方米）旁边建模一小盒海洋。这将为冰附近的湍流及其与熔化的相互作用提供见解。然后，我们将使用大涡模拟（LES）在高分辨率（〜10厘米-1米）下研究较大的体积（面积约1平方公里）。这将解决整个边界层中最大的湍流运动。这两种模型均可使用从乔治六世和拉尔森C冰架上的系泊点获得的最新观察结果进行验证（Nicholls，NE/H009205/1）。模型结果反过来将有助于解释和理解观测值。我们将使用这些数值模型来设计和校准参数化，以用于冰融化和垂直混合以在海洋气候模型中使用。我们将为一维（垂直）模型添加候选参数化，该模型包含许多流行的海洋混合方案，并直接根据DNS和LES结果进行测试。我们将从现有的参数分析开始，并根据需要对其进行修改，以匹配高分辨率模型。成功的参数将在英国海洋模型（NEMO）中实施，并与气候建模组（包括大都会办公室）共享，以改善海平面上升的预测。

项目成果

Double Diffusion As a Driver of Turbulence in the Stratified Boundary Layer Beneath George VI Ice Shelf

双扩散作为乔治六世冰架下分层边界层湍流的驱动因素

• DOI: 10.1029/2021gl096119
• 发表时间: 2022
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Middleton L

Turbulence in the Ice Shelf-Ocean Boundary Current and Its Sensitivity to Model Resolution

冰架-海洋边界流中的湍流及其对模型分辨率的敏感性

• DOI: 10.1175/jpo-d-22-0034.1
• 发表时间: 2023
• 期刊: Journal of Physical Oceanography
• 影响因子: 3.5
• 作者: Patmore R

A general criterion for the release of background potential energy through double diffusion

通过双扩散释放背景势能的一般准则

• DOI: 10.1017/jfm.2020.259
• 发表时间: 2020
• 期刊: Journal of Fluid Mechanics
• 影响因子: 3.7
• 作者: Middleton L

Stratification effects in the turbulent boundary layer beneath a melting ice shelf: Insights from resolved large-eddy simulations

融化冰架下湍流边界层的分层效应：解析大涡模拟的见解

• DOI: 10.17863/cam.39552
• 发表时间: 2019
• 作者: Vreugdenhil C

Large-eddy simulations of stratified plane Couette flow using the anisotropic minimum-dissipation model

使用各向异性最小耗散模型对分层平面库埃特流进行大涡模拟

• DOI: 10.17863/cam.32401
• 发表时间: 2018
• 作者: Vreugdenhil C