How Accurately Should We Model Ice Shelf Melt Rates?

Assessment of ocean-forced ice sheet loss requires that ocean models be able to represent sub-ice shelf melt rates. However, spatial accuracy of modeled melt is not well investigated, and neither is the level of accuracy required to assess ice sheet loss. Focusing on a fast-thinning region of West Antarctica, we calculate spatially resolved ice-shelf melt from satellite altimetry and compare against results from an ocean model with varying representations of cavity geometry and ocean physics. Then, we use an ice-flow model to assess the impact of the results on grounded ice. We find that a number of factors influence model-data agreement of melt rates, with bathymetry being the leading factor; but this agreement is only important in isolated regions under the ice shelves, such as shear margins and grounding lines. To improve ice sheet forecasts, both modeling and observations of ice-ocean interactions must be improved in these critical regions.Plain Language Summary The Antarctic coastline is fringed by large floating ice shelves, often the size of cities or larger. They play a crucial role as a stopgap against acceleration of the ice sheet, and their loss could lead to considerable sea level rise. Many of these ice shelves are exposed to warm waters from farther north, leading to considerable melting underneath. Scientists use models of the ice sheet and the ocean in order to understand the link between warming oceans and sea levels, and how this might change in the future. In our study we focus on one of these fast-thinning ice shelves and determine through satellite imagery that melting is not uniform across the ice shelf but is highly focused in certain areas due to ocean currents. Using state-of-the-art ice and ocean models, we investigate what information will be needed in order to predict how the Antarctic Ice Sheet will respond to climate change. Our findings suggest that improved knowledge of ocean depth under ice shelves, as well as improved understanding of ocean flow just below the ice bottom, will be vital in determining the effects of climate change on ice shelves and ice sheets.

评估海洋驱动的冰盖损失要求海洋模型能够呈现冰架下的融化速率。然而，模拟融化的空间准确性尚未得到充分研究，评估冰盖损失所需的准确性水平也未得到充分研究。聚焦于西南极洲一个快速变薄的区域，我们通过卫星测高法计算空间分辨率的冰架融化情况，并与一个对空洞几何形状和海洋物理有不同呈现的海洋模型的结果进行比较。然后，我们使用一个冰流模型来评估这些结果对陆地冰的影响。我们发现，许多因素影响融化速率的模型 - 数据一致性，其中海底地形是首要因素；但这种一致性仅在冰架下的孤立区域（如剪切边缘和接地线）很重要。为了改进冰盖预测，在这些关键区域必须改进对冰 - 海相互作用的建模和观测。 通俗语言概要：南极海岸线被大型漂浮冰架环绕，这些冰架通常有城市那么大，甚至更大。它们作为阻止冰盖加速的临时措施起着至关重要的作用，它们的消失可能导致海平面大幅上升。许多这些冰架暴露于来自更北方的温暖海水，导致其下方大量融化。科学家使用冰盖和海洋模型来了解海洋变暖与海平面之间的联系，以及未来这种情况可能如何变化。在我们的研究中，我们聚焦于其中一个快速变薄的冰架，并通过卫星图像确定，整个冰架的融化并不均匀，而是由于洋流在某些区域高度集中。利用最先进的冰和海洋模型，我们研究为了预测南极冰盖将如何对气候变化作出反应需要哪些信息。我们的研究结果表明，更好地了解冰架下的海洋深度，以及更好地理解冰底下方的洋流，对于确定气候变化对冰架和冰盖的影响至关重要。