Exploring Recent Changes of Ocean Salinity Distributions in the Context of Climate Change

探索气候变化背景下海洋盐度分布的近期变化

• 批准号: 0326778
• 负责人: Ruth Curry
• 金额: $ 48.37万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-09-01 至 2006-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0326778&HistoricalAwards=false
• 关键词: Exploring; Recent; Changes; Ocean; Salinity

Because the hydrologic cycle remains one of the least well understood aspects of the climate system, and freshwater forcing the most probable cause for differences among climate models, the proposed research will provide an important observational foundation for evaluating ongoing and future changes in Earth's climate. Over the past fifty years, ocean salinity distributions have been changing and the accumulating observational record is beginning to suggest some trends of near global extent. Various studies have individually documented salinity increases in tropical and subtropical surface waters of the Indo-Pacific, Atlantic and Mediterranean in recent decades; while over the same time period, the intermediate and deep water masses, ventilated at higher latitudes in both hemispheres, have become increasingly fresh. The proposed research will investigate whether these apparently large-scale and hemispherically symmetric shifts in ocean salinity distribution can provide evidence of a change in the planetary hydrologic cycle. It will engage in comparing the observed rates of freshwater gains and losses in the ocean to results from climate model simulations. Reflecting model predictions that the hydrologic cycle may have climatically important effects on the thermohaline circulation (THC), the study will evaluate the impacts of the observed changes in salinity and freshwater distributions on ocean density. A systematic census of ocean property content changes will be conducted for the Pacific, Atlantic, Arctic, and Nordic Seas from 30 degrees S to 90 degrees N utilizing new climatology products and tools. Volumetric integrals of salt will be used to identify first order changes in ocean freshwater transports over the instrumental record and to estimate E-P anomalies for the ventilated ocean layers. These anomalies will be compared to the latest evaporation and precipitation climatology products derived from other sources. Combining the Bergen Coupled Model with observations, the time-dependent formation and subduction rates for Salinity Maximum Waters will be investigated in conjunction with researchers at Laboratoire d' Oceanographie Dynamique et de Climatologie (LODYC) in Paris, France. The observational analyses will also be compared to results from NOAA's Geophysical Fluid Dynamics Laboratory (GFDL) coupled ocean-atmosphere models. These comparisons will assess the degree to which the model projected changes in salinity resemble the observed changes and provide perspective on whether they represent a signal of any significance against the background variability of the climate system. Finally, the amplitude of the dramatic freshening of the water column that has occurred in the northern North Atlantic will be assessed in the context of threshold values for the THC, as determined from model simulations. Broader Impacts: The broader impacts of this study are likely to be threefold. First, it will establish collaboration among researchers from several groups, i.e., modelers and observationalists from WHOI, GFDL, and LODYC. Second, the model-data comparisons will constitute a powerful tool for calibrating climate simulations and may be a significant stimulus for further model experiments to diagnose the mechanisms of hydrologic changes. Third, the larger research community will benefit from the expansion of the HydroBase quality-controlled database and gridded climatology products which will result from this work.

由于水文循环仍然是气候系统中最鲜为人知的方面之一，并且淡水迫使气候模型之间造成差异的最可能原因，因此拟议的研究将为评估地球气候中正在进行的和未来的变化提供重要的观察基础。在过去的五十年中，海洋盐度分布一直在发生变化，累积的观察记录开始暗示了一些几乎全球范围的趋势。 近几十年来，各种研究已经证明了印度太平洋，大西洋和地中海的热带和亚热带地表水的盐度增加。虽然在同一时期，在两个半球的较高纬度上通风的中间和深水质量变得越来越新鲜。 拟议的研究将研究这些显然是大规模和半球形的海洋盐度分布的对称转移是否可以提供行星水文周期变化的证据。 它将参与比较观察到的海洋中淡水收益和损失的速度与气候模型模拟的结果。反映模型的预测，即水文周期可能对热盐循环（THC）具有重要影响，研究将评估观察到的盐度变化和淡水分布对海洋密度的影响。通过新的气候产品和工具，将对太平洋，大西洋，北极和北欧海洋进行系统的人口普查变化，从30度到90度。 盐的体积积分将用于确定仪器记录上海洋淡水运输的一阶变化，并估算通风的海洋层的E-P异常。 这些异常将与来自其他来源的最新蒸发和降水气候产品进行比较。将卑尔根耦合模型与观察结果相结合，将与法国巴黎巴黎的Laboratoire D'Eceanogriphie Dynamegrie et de climatologie（Lodyc）的研究人员一起研究盐度最大水的时间依赖性形成和俯冲率。观察分析还将与NOAA的地球物理流体动力学实验室（GFDL）耦合的海洋 - 大气模型的结果进行比较。 这些比较将评估模型预测盐度变化的程度类似于观察到的变化，并提供了它们是否代表对气候系统背景变异性具有任何意义的信号。 最后，根据模型模拟确定，将在THC的阈值阈值中评估水柱的急剧清新化幅度。 更广泛的影响：这项研究的更广泛影响可能是三倍。 首先，它将在几个小组的研究人员之间建立合作，即来自WHOI，GFDL和Lodyc的建模者和观察家。 其次，模型数据比较将构成校准气候模拟的强大工具，并且可能是进一步模型实验的重要刺激，以诊断水文变化的机制。 第三，较大的研究界将受益于液化酶质量控制的数据库和栅格气候产品的扩展，这将源于这项工作。