Variability of Internally Generated Turbulence in an Estuary, from 100 Days of Continuous Observations.

Orton, P. M. and Visbeck, Martin (2009) Variability of Internally Generated Turbulence in an Estuary, from 100 Days of Continuous Observations. Continental Shelf Research, 29 (1). pp. 61-77. DOI 10.1016/j.csr.2007.07.008.

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Abstract

We present detailed observations of internally generated turbulence in a sheared, stratified natural flow, as well as an analysis of the external factors leading to its generation and temporal variability. Multi-month time series of vertical profiles of velocity, acoustic backscatter (0.5 Hz), and turbulence parameters were collected with two moored acoustic Doppler current profilers (ADCPs) in the Hudson River estuary, and estuary-long transects of water density were collected 30 times. ADCP backscatter is used for visualization of coherent turbulent structures and evaluation of surface wave biases to the turbulence measurements. Benefits of the continuous long-term turbulence record include our capturing: (1) the seasonality of turbulence due to changing riverflow, (2) hysteresis in stratification and turbulence over the fortnightly cycle of tidal range, and (3) intermittent events such as breaking internal waves. Internal mixing layers (IMLs) are defined as turbulent regions above the logarithmic velocity layer, and the bottom boundary layer (BBL) is defined as the continuously turbulent range of heights above the bed. A cross-correlation analysis reveals how IML and BBL turbulence vary with stratification and external forcing from tidal range, river flow, and winds. Turbulence in both layers is maximal at spring tide and minimal when most stratified, with one exception IML turbulence at a site with changing channel depth and width is maximal at times of maximum stratification and freshwater input.

Document Type: Article
Keywords: USA; New York; Hudson river; vertical mixing; turbulence; measurement estuary reynolds stresses acoustic doppler current profiler partially stratified estuary partially mixed estuary reynolds stress tidal channel shear instability tke production shelf seas flow dissipation transport
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
OceanRep > The Future Ocean - Cluster of Excellence
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.csr.2007.07.008
ISSN: 0278-4343
Projects: Future Ocean, Collaborative Research, Determining the Air–Water CO2 Flux in Coastal Systems
Date Deposited: 08 Jan 2009 11:54
Last Modified: 21 Sep 2016 07:44
URI: http://oceanrep.geomar.de/id/eprint/7388

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