Modelling of oil thickness in the presence of an ice edge

Tor Nordam,Emma Litzler,Jørgen Skancke,Ivar Singsaas,Frode Leirvik,Øistein Johansen

doi:10.1016/j.marpolbul.2020.111229

Tor Nordam, Emma Litzler + Show 4 more

Open Access

https://doi.org/10.1016/j.marpolbul.2020.111229

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Abstract

Oil slick thickness is a key parameter for the behaviour of oil spilled at sea. It influences evaporation and entrainment, viable response options, and the risk to marine life at the surface. Determining this value is therefore of high relevance in oil spill modelling. In open water, oil can spread as thin films due to gravity alone, and may be further dispersed by horizontal diffusion and differential advection. In the presence of ice, however, a thin oil slick may become concentrated to higher thickness, if compressed against the ice edge.In the present study, we develop a simple model for the thickness of oil forced against a barrier by a current. We compare our theory to flume experiments, and obtain reasonable agreement. We describe an implementation in a Lagrangian oil spill model, and present some examples. We discuss the operational applicability, and suggest further research needs.

Highlights

Oil spill modelling is commonly used to assist planning of contingency and response options in case of accidental oil spills during production or exploration
We propose to define the ice edge to consist of those grid cells where the ice coverage is lower than 70% and at minimum one nearest-neighbor cell has an ice coverage greater than or equal to 70%
Applicability of the model to real conditions In the derivation of the equation for oil thickness against an ice Prediction of surface oil thickness is a fundamental challenge in oil spill modelling

Summary

Introduction

Oil spill modelling is commonly used to assist planning of contingency and response options in case of accidental oil spills during production or exploration. The aim of modelling in the planning phase is to predict probable locations where the oil will end up, and to quantify how much oil might be stranded, submerged, or remain at the surface. A key target for modelling is to predict the state of surface oil, as this impacts the further fate of the spill and what response options are viable. A complete marine oil spill model must account for a range of processes that affect oil at sea, including spreading, transport, mixing, evaporation, emulsification, and biodegradation. Oil in a broken ice field tends to evaporate and emulsify more slowly than oil in open water, due to reduced surface area and typically low temperatures (Brandvik and Faksness, 2009). Biodegradation rates are reduced in low temperatures (Bagi et al, 2013; Lofthus et al, 2018; Nordam et al, 2020)

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