Comparative Effects of Climate Change and Tidal Stream Energy Extraction in a Shelf Sea

Michela De Dominicis,Rory O'Hara Murray,Judith Wolf

doi:10.1029/2018jc013832

Abstract

AbstractThe environmental implications of tidal stream energy extraction need to be evaluated against the potential climate change impacts on the marine environment. Here we study how hypothetical very large tidal stream arrays and a business as usual future climate scenario can change the hydrodynamics of a seasonally stratified shelf sea. The Scottish Shelf Model, an unstructured grid three‐dimensional ocean model, has been used to reproduce the present and the future state of the NW European continental shelf. Four scenarios have been modeled: present conditions and projected future climate in 2050, each with and without very large scale tidal stream arrays in Scottish Waters (UK). It is found that where tidal range is reduced a few centimeters by tidal stream energy extraction, it can help to counter extreme water levels associated with future sea level rise. Tidal velocities, and consequently tidal mixing, are also reduced overall by the action of the tidal turbine arrays. A key finding is that climate change and tidal energy extraction both act in the same direction, in terms of increasing stratification due to warming and reduced mixing; however, the effect of climate change is an order of magnitude larger.

Highlights

It is widely recognised that there is a pressing need to mitigate the effects of anthropogenically induced climate change and other environmental impacts of worldwide reliance on fossil fuels
The present paper is focused on tidal stream energy extraction and addresses the following questions: (i) how can marine energy developments affect ocean hydrodynamic processes that can be relevant for ecosystem habitats and animals’ behaviour? (ii) how can we differentiate the effects of climate change from energy extraction? (iii) are there ways in which the deployment of marine renewables may ameliorate or exacerbate the predicted effects of climate change? The results presented in this paper are being used by further studies to understand how the physical changes will translate into impacts on ecosystem habitats and animals’ behaviour
3.8 GW is a realistic estimate of the average instantaneous power that can be provided from Scottish Waters. Such large-scale tidal stream energy extraction is unlikely to occur in the near future, since very large numbers of devices are required

Summary

Introduction

It is widely recognised that there is a pressing need to mitigate the effects of anthropogenically induced climate change and other environmental impacts of worldwide reliance on fossil fuels. The more recent IPCC AR5 [Fifth Assessment Report, Stocker et al, 2013] brought even more certainty in these conclusions and “well below 2◦ C above pre-industrial levels” is the global temperature warming limit to which over 160 governments around the world have signed up with the Paris Agreement in 2015. This widespread concern has led to a growing interest in alternative energy sources. There is a pressing need to further diversify the low-carbon generation capacity and more attention is being fo-

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