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GCE III - Key Finding in 2016

    3-d model tracks residence times and shows connectivity in GCE estuaries

    The residence time of an estuary, which is the average amount of time that a water particle spends in the system (or a portion thereof), is often thought of as a controlling variable: the longer the residence time, the more opportunity for biological and chemical transformations. Although GCE investigators have previously estimated a variety of transit times for riverine estuaries (Sheldon and Alber 2002, 2006), these earlier studies relied on simplifying assumptions. However, the implementation of the hydrodynamic FVCOM model allows us to use Lagrangian particle tracking to produce highly detailed maps of residence time. Wang et al. (2017) found a general tendency for residence time to increase with increasing distance from the ocean, with the longest times in small creeks near the head of the estuary. These areas are also the most likely to be developed, which means that any input of contaminants or nutrients in those areas would have a longer time to affect water quality. In addition to residence time, another factor that affects estuarine dynamics is water exchange between adjacent estuaries (Di Iorio and Castelao 2013). Wang et al. (2016) used FVCOM to evaluate connectivity and transport patterns by tracking particle movement between estuaries. They found a high degree of connectivity between the Altamaha River and Doboy Sound as well as evidence for coastal exchange (i.e. particles transported out of one estuary that enter in through the mouth of another) (Fig. 1). These insights into both residence times and connectivity can now be used to help interpret field studies, and provide us with a powerful tool we can use to make predictions regarding nutrient distribution, larval transport, and many other aspects of ecosystem dynamics.


    Fig. 1 Connectivity among estuaries in the FVCOM model of the GCE domain, determined based on particles released at various locations in the model. Particles released at some locations stayed within their respective estuaries (cyan, red, blue), while others visited two or all three estuaries. From Wang et al. (2016).


This material is based upon work supported by the National Science Foundation under grants OCE-9982133, OCE-0620959, OCE-1237140 and OCE-1832178. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.