Water temperature in estuaries: river and ocean influences, effects of surface heat flux, and dynamical role of temperature stratification

河口水温：河流和海洋的影响、表面热通量的影响以及温度分层的动力作用

• 批准号: 1949067
• 负责人: Melanie Fewings
• 金额: $ 79.99万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-03-15 至 2025-02-28
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1949067&HistoricalAwards=false
• 关键词: Water; temperature; estuaries; river; ocean

Estuaries are biologically productive areas of the ocean that support important fisheries and coastal ecosystems. However, they are under stress from changing river flows and weather patterns, nutrient loading, hypoxia, and harmful algal blooms. Water temperature is a major influence on algal growth rates and affects nutrient cycling rates. Increasing temperature results in lower dissolved oxygen saturation values, and higher respiration rates of organisms, increasing community respiration; therefore, warmer water can directly lead to worsening hypoxia, which is already a nationally and globally increasing problem. At higher temperatures, oysters are more susceptible to disease and less able to tolerate freshening of the water column. Fish and crustaceans have thermal tolerance limits, and some species of fish already experience thermal stress during current warm water anomalies. The processes that control water temperature in estuaries have received little attention in comparison to salinity, which is the main control on the density field and estuarine circulation. This project will determine how estuarine water temperature is dynamically controlled and understand which processes, including estuarine basin geometry, are more important. The study will use existing data and semi-idealized numerical simulations from seven mid latitude estuaries. These are ecosystems likely to experience increased thermal stress in coming decades, when precipitation, river flow, wind, air temperature, and cloudiness patterns, all of which impact estuarine temperatures, are forecast to change. This project will support a graduate student.Although temperature is as important as salinity in its effects on the ecology of estuaries, the existing physical oceanographic literature provides little to no framework for understanding the temperature structure, variability, and dynamics of estuaries. The major influences on water temperature in estuaries are (1) conservative mixing of ocean and river waters with different temperature as water parcels are advected through the estuary and (2) air-sea heat exchange. In rapidly flushed estuaries, the water temperature is determined by conservative mixing, so temperature could be predicted from the salinity field and the river and ocean temperatures. In slowly flushed estuaries, however, these river and ocean end member temperatures vary on time scales shorter than the transit time of water parcels passing through the estuary, making conservative mixing less useful as a basis for predicting temperature. Further, in slowly flushed estuaries, air-sea heat fluxes cause the water temperature to depart from the conservative mixing prediction. This project will determine what controls the structure and evolution of water temperature in seven estuaries across a broad range of parameter space and provide a framework for understanding other estuarine systems. The investigators will develop an analytical framework for understanding the dynamics that control estuarine water temperature and identify non-dimensional parameters that govern the temperature structure. The new framework will be tested by synthesizing existing long time series observations of seven estuaries (the Delaware Bay, Chesapeake Bay, Hudson River, Merrimack River, Columbia River, Alsea River, and Guadalquivir River) that span a range of parameter space. As part of this research, the range of natural variability in estuarine temperatures and forcing (i.e., air-sea fluxes and time-varying river and ocean temperatures) will be determined and its relation to estuary depth and transit time will be examined using idealized numerical model experiments. The main hypothesis to be tested is that vertical temperature stratification has substantial dynamical effects by modifying vertical mixing in regions of marginal stability, changing the estuarine circulation and length of the salt intrusion.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

河口是海洋的生物生产区，支持着重要的渔业和沿海生态系统。然而，它们受到河流流量和天气模式变化、营养负荷、缺氧和有害藻华的压力。水温是影响藻类生长速率和养分循环速率的主要因素。温度升高导致溶解氧饱和度降低，生物体呼吸速率升高，群落呼吸增加；因此，海水变暖会直接导致缺氧恶化，这已经是一个国家和全球日益严重的问题。在较高的温度下，牡蛎更容易生病，也更不能忍受水柱的新鲜。鱼类和甲壳类动物有热容忍度限制，一些鱼类在当前的暖水异常期间已经经历了热应激。盐度是密度场和河口环流的主要控制因素，而控制河口水温的过程却很少受到重视。该项目将确定河口水温是如何动态控制的，并了解哪些过程更重要，包括河口盆地几何形状。这项研究将使用来自七个中纬度河口的现有数据和半理想化的数值模拟。这些生态系统在未来几十年可能会经历更大的热应力，届时降水、河流流量、风、气温和云量模式都会发生变化，所有这些都会影响河口温度。这个项目将资助一名研究生。虽然温度对河口生态的影响与盐度一样重要，但现有的物理海洋学文献几乎没有提供理解河口温度结构、变化和动态的框架。对河口水温的主要影响有：(1)不同温度的海洋和河流水的保守混合，因为水包通过河口平流；(2)海气热交换。在快速冲刷的河口，水温是由保守混合决定的，因此可以通过盐度场和河流和海洋温度来预测温度。然而，在缓慢冲刷的河口，这些河流和海洋末端成员的温度变化在时间尺度上比水包通过河口的时间短，这使得保守混合作为预测温度的基础不太有用。此外，在缓慢冲刷的河口，海气热通量导致水温偏离保守的混合预测。该项目将在广泛的参数空间范围内确定控制七个河口水温结构和演变的因素，并为理解其他河口系统提供框架。研究人员将开发一个分析框架，以了解控制河口水温的动力学，并确定控制温度结构的无量纲参数。新的框架将通过综合现有的七个河口（特拉华湾、切萨皮克湾、哈德逊河、梅里马克河、哥伦比亚河、阿尔西河和瓜达尔基维尔河）的长时间序列观测来进行测试，这些河口跨越了一系列参数空间。作为这项研究的一部分，将确定河口温度和强迫（即海气通量和随时间变化的河流和海洋温度）的自然变率范围，并利用理想数值模式实验检验其与河口深度和过境时间的关系。拟验证的主要假设是，垂直温度分层通过改变边缘稳定区域的垂直混合、改变河口环流和盐侵入的长度而具有实质性的动力效应。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

The Evolution of a Northward‐Propagating Buoyant Coastal Plume After a Wind Relaxation Event

风弛豫事件后向北传播的浮力沿海羽流的演变

• DOI: 10.1029/2021jc017720
• 发表时间: 2021
• 期刊: Journal of Geophysical Research: Oceans
• 作者: McSweeney, Jacqueline M.;Fewings, Melanie R.;Lerczak, James A.;Barth, John A.
• 通讯作者: Barth, John A.

Curves, Coriolis, and Cross-Channel Circulation in the Hudson River Estuary

哈德逊河口的曲线、科里奥利力和跨海峡环流

• DOI: 10.1175/jpo-d-23-0093.1
• 发表时间: 2024
• 期刊: Journal of Physical Oceanography
• 影响因子: 3.5
• 作者: Conley, Margaret M.;Lerczak, James A.
• 通讯作者: Lerczak, James A.