A 30-Year History of Tide and Current Measurements in Elkhorn Slough, California

Broenkow, William W. and Breaker, Laurence, C. (2005) A 30-Year History of Tide and Current Measurements in Elkhorn Slough, California. Moss Landing, CA, Moss Landing Marine Laboratories,

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Abstract

Elkhorn Slough was first exposed to direct tidal forcing from the waters of Monterey Bay with the construction of Moss Landing Harbor in 1946. Elkhorn Slough is located mid-way between Santa Cruz and Monterey close to the head of Monterey Submarine Canyon. It follows a 10 km circuitous path inland from its entrance at Moss Landing Harbor. Today, Elkhorn Slough is a habitat and sanctuary for a wide variety of marine mammals, fish, and seabirds. The Slough also serves as a sink and pathway for various nutrients and pollutants. These attributes are directly or indirectly affected by its circulation and physical properties. Currents, tides and physical properties of Elkhorn Slough have been observed on an irregular basis since 1970. Based on these observations, the physical characteristics of Elkhorn Slough are examined and summarized. Elkhorn Slough is an ebb-dominated estuary and, as a result, the rise and fall of the tides is asymmetric. The fact that lower low water always follows higher high water and the tidal asymmetry produces ebb currents that are stronger than flooding currents. The presence of extensive mud flats and Salicornia marsh contribute to tidal distortion. Tidal distortion also produces several shallow water constituents including the M3, M4, and M6 overtides and the 2MK3 and MK3 compound tides. Tidal elevations and currents are approximately in quadrature; thus, the tides in Elkhorn Slough have some of the characters of a standing wave system. The temperature and salinity of lower Elkhorn Slough waters reflect, to a large extent, the influence of Monterey Bay waters, whereas the temperature and salinity of the waters of the upper Slough (>5 km from the mouth) are more sensitive to local processes. During the summer, temperature and salinity are higher in the upper slough due to local heating and evaporation. Maximum tidal currents in Elkhorn Slough have increased from approximately 75 to 120 cm/s over the past 30 years. This increase in current speed is primarily due to the change in tidal prism which has increased from approximately 2.5 to 6.2 x 106 m3 between 1956 and 1993. The increase in tidal prism is the result of both 3 rapid man-made changes to the Slough, and the continuing process of tidal erosion. Because of the increase in the tidal prism, the currents in Elkhorn Slough exhibit positive feedback, a process with uncertain consequences. [PDF contains 55 pages]

Item Type: Monograph or Serial Issue
Title: A 30-Year History of Tide and Current Measurements in Elkhorn Slough, California
Personal Creator/Author:
CreatorsEmail
Broenkow, William W.
Breaker, Laurence, C.
Date: 2005
Publisher: Moss Landing Marine Laboratories
Place of Publication: Moss Landing, CA
Latitude: 36.8472
Longitude: 121.778
Issuing Agency: Moss Landing Marine Laboratories
Subjects: Oceanography
Item ID: 3128
Depositing User: Joan Parker
Date Deposited: 08 Apr 2010 12:42
Last Modified: 29 Sep 2011 17:53
URI: http://aquaticcommons.org/id/eprint/3128

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