Abstract
AbstractAn overflow of dense cold water from the Faroese Channels across the Wyville Thomson Ridge (WTR) into the Rockall Trough was recorded during the 136th cruise of the RRS James Cook in June 2016. This event happened in the eastern part of the ridge. The remotely operated vehicle ISIS deployed for a collection of coral samples recorded an abrupt drop in temperature at 500‐m depth. Specifically, the water temperature decreased from 8.73 to 6.74 °C and salinity from 35.26 to 35.16. This rapid drop happened over 20 min, with the fastest rate of water temperature decrease of 1.10 °C occurring just over 1 min 50 s. The numerical modeling conducted to reproduce the event has shown that a massive overflow took place in the WTR section, which is close to the Darwin Mounds. The overflow has led to resuspension of bottom sediments; the remotely operated vehicle sampling program in the area of the Darwin Mounds terminated due to low visibility. The numerical experiments have shown that tidally induced overflows over the WTR can occur periodically under spring tidal conditions. The model allowed us to identify two places in the eastern part of the WTR where the tidally driven overflows more realistically can happen.
Highlights
The water exchange across the Greenland-Iceland-Scotland Ridge is a part of the Atlantic Meridional Overturning Circulation
The across-ridge tidal oscillations resulted in an ultimate spillage of the Faroe-Shetland Channel Bottom Water (FSCBW) over the Wyville Thomson Ridge (WTR), Figure 9
The upper boundary of the cold Norwegian Sea Deep Water flowing along the Faroe Bank Channel (FBC) is at the level of the WTR crest
Summary
The water exchange across the Greenland-Iceland-Scotland Ridge is a part of the Atlantic Meridional Overturning Circulation. The Wyville Thomson Ridge (WTR) separates the FSC and FBC from the southerly located Rockall Trough (RT), a steep-sided, deep water basin This ridge, with its sill depth of 400–500 m, is a natural geological barrier that prevents penetration of the cold Faroe-Shetland Channel Bottom Water (FSCBW) from FSC to RT (see Figure 1a). In the present paper we analyze the observational data set that shows an alternative spill location for the WTR overflow This event occurred in the eastern section of the WTR in June 2016 during the 136th cruise of the RRS James Cook. The overflow that happened in the eastern section of the WTR (along red doted line, Figure 1b) resulted in a resuspension of bottom sediments that made all further ROV samplings in the RT area impossible The analysis of this unusual overflow event and its driving forces is a principal goal of the present paper. The paper ends with the discussion and conclusions of the study
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