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，支持重要的渔业和沿海生态系统。然而，它们面临着河流流量和天气模式变化、营养物质负荷、缺氧和有害藻类水华的压力。水温是影响藻类生长速率和营养循环速率的主要因素。温度升高会导致溶解氧饱和度降低，生物体的呼吸速率增加，从而增加社区呼吸；因此，水变暖会直接导致缺氧恶化，这已经是一个全国性和全球性的日益严重的问题。在较高的温度下，牡蛎更容易受到疾病的影响，更不能容忍水柱的新鲜。鱼类和甲壳类动物有耐热性极限，在当前暖水异常期间，一些鱼类已经经历了热应激。与盐度相比，控制河口水温的过程较少受到关注，盐度是控制密度场和河口环流的主要因素。这个项目将确定河口水温是如何动态控制的，并了解哪些过程，包括河口盆地的几何形状，更重要。这项研究将使用现有的数据和来自七个中纬度河口的半理想化数值模拟。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、气温和云量模式都将发生变化，所有这些都会影响河口温度。尽管温度和盐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很少或根本没有为理解河口的温度结构、变异性和动态提供框架。影响河口水温的主要因素有：(1)水团平流通过河口时，不同温度的海水和河流的保守混合；(2)海气热交换。在快速冲刷的河口，水温是由保守的混合决定的，因此可以根据盐度场以及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在时间尺度上的变化比通过河口的水团的传输时间短，这使得保守的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。该项目将确定是什么控制了七个河口水温的结构和演变，涉及广泛的参数空间，并为了解其他河口系统提供了一个框架。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，海气通量以及河流和海洋温度的时变)的自然变化范围，并将通过理想化的数值模式实验来研究其与河口深度和渡越时间的关系。需要检验的主要假设是，垂直温度分层通过改变边缘稳定区的垂直混合，改变河口环流和盐类入侵的长度，具有实质性的动力效应。这一裁决反映了NSF的法定使命，并通过使用基金会的智力优势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.