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Falmouth 2015 - Group 1

Introduction

Aim: To identify the position of the tidal front.

Tidal fronts develop between seasonally stratified deeper waters and the shallower water which are dominated by tidal mixing. The strength of mixing is important in how a tidal front is created and the hydrography and circulation at the front is important for the biological processes that lead to cross frontal transport (Sun and Cho 2010). For this reason is it important that this physical feature is also studied from a biological and chemical perspective.

On 22/06/2015 we travelled offshore from the port of Falmouth onboard RV Callista. We collected underway data continuously from 10:15 UTC to 17:00 UTC for salinity, temperature, oxygen and fluorescence, and also ADCP data, providing information on current speed and backscatter. This underway data then allowed us to identify locations where we wanted to deploy our CTD, their location can be seen in figure 1. On each CTD cast we recorded temperature, salinity, irradiance and fluorescence. At locations 1,2 and 4 we also took water samples and a vertical 200μm net trawl to collect samples of zooplankton; we later analyses the water samples in the lab for phytoplankton, and chlorophyll, nitrate, phosphate, silicate and oxygen concentrations. At station 3 only minimal data was collected as this was an investigative station, and we decided to move closer to shore before taking more water samples.

A breakdown of the data that was collected and a brief analysis can be found in the chemical, biological and physical sections.

Figure 1- Google earth image showing positions of stations where CTD casts were taken. Each number corresponds to the station number (Google Earth).

Table 1: Metadata for the offshore trip on 22/06/2015

References:

Google earth V 6.2.2.6613. (May 11, 2009). Falmouth, England. 50° 06’ 05.83”N, 004° 54’ 20.56”W, Eye alt 38.46km. DigitalGlobe 2015. http://www.earth.google.com [June 24, 2015]

Sun, Y and Cho,Y. (2010). Tidal front and its relation to the biological process in coastal water. Ocean Science Journal. 45 (4), p243-251.

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Disclaimer: The views expressed here are not associated with those of the National Oceanography Centre Southampton or the University of Southampton.

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