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，它们正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。水温是藻类生长速率的主要影响因素，并影响营养循环速率。温度升高导致溶解氧饱和度值降低，生物体呼吸速率升高，增加群落呼吸;因此，水温升高可直接导致缺氧恶化，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，牡蛎更容易受到疾病的影响，也更不能忍受水柱的清新。鱼类和甲壳类动物有热耐受极限，在目前的温水异常期间，一些鱼类已经经历了热应力。控制河口水温的过程很少受到关注，相比之下，盐度是密度场和河口环流的主要控制因素。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，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半理想化的数值模拟从七个中纬度河口。这些生态系统可能会在未来几十年内经历越来越多的热应力，届时降水、河流流量、风、气温和云量模式都会影响河口温度，预计这些都会发生变化。虽然温度和盐度对河口生态的影响一样重要，但现有的物理海洋学文献几乎没有为理解河口的温度结构、变率和动力学提供任何框架。影响河口水温变化的主要因素是：（1）不同温度的海洋和河流沃茨在河口平流时的保守混合;（2）海气热交换。在快速冲刷的河口，水温是由保守混合决定的，所以温度可以从盐度场和河流和海洋温度预测。然而，在缓慢冲洗的河口，这些河流和海洋端部成员的温度变化的时间尺度短于通过河口的水包裹的过境时间，使保守的混合作为预测温度的基础不太有用。此外，在缓慢冲洗河口，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在广泛的参数空间的水温结构和演变，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态，并确定控制温度结构的无量纲参数。新的框架将进行测试，综合现有的长时间序列观测的七个河口（特拉华州湾，切萨皮克湾，哈德逊河，梅里马克河，哥伦比亚河，阿尔西河，瓜达尔基维尔河），跨越一系列的参数空间。作为这项研究的一部分，河口温度和强迫的自然变化范围（即，海气通量和随时间变化的河流和海洋温度），并将使用理想化的数值模型实验来研究其与河口深度和过境时间的关系。要测试的主要假设是，垂直温度分层有很大的动力学效应，通过修改边缘稳定区域的垂直混合，改变河口环流和长度的盐intrusion.This奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

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.