Sea ice effects on the upper ocean: internal waves, ice-covered gyres and the seasonal ice zone
The polar oceans are currently experiencing significant changes. Arctic and Antarctic sea ice extent and volume are changing, with a poorly constrained implication for future climate. Understanding the interactions between sea ice and the underlying ocean is fundamental for understanding current cha...
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ftuloxford:oai:ora.ox.ac.uk:uuid:6764666b-92ef-41fa-890f-0d810cc2bade 2023-05-15T14:00:11+02:00 Sea ice effects on the upper ocean: internal waves, ice-covered gyres and the seasonal ice zone Thielen, K Wells, A 2021-09-20 https://ora.ox.ac.uk/objects/uuid:6764666b-92ef-41fa-890f-0d810cc2bade eng eng https://ora.ox.ac.uk/objects/uuid:6764666b-92ef-41fa-890f-0d810cc2bade info:eu-repo/semantics/openAccess CC Attribution (CC BY) CC-BY Thesis 2021 ftuloxford 2022-06-28T20:14:17Z The polar oceans are currently experiencing significant changes. Arctic and Antarctic sea ice extent and volume are changing, with a poorly constrained implication for future climate. Understanding the interactions between sea ice and the underlying ocean is fundamental for understanding current changes, and predicting future ice-states. In this thesis I study several aspects of the under-ice boundary layer and the coupling to the deeper polar ocean. First, I conduct numerical simulations of fluid flow using the Lattice Boltzmann Method to investigate the effects of stratification and roughness on ice-ocean drag and heat flux below a ridged ice floe overlaying a stably stratified ocean. It is found that sea ice generated internal waves can cause order of magnitude variations in the simulated drag coefficient and modest variations in area-integrated heatflux and its spatial distribution. A parameterization is developed for wave drag as a scaling law in terms of upper ocean velocity, stratification, and ridge geometry. To understand the potential impact, this parameterization is applied to an idealized conceptual model of an ice-covered ocean gyre. The model extends previous descriptions of ocean density variation subject to applied wind stress to account for ice-ocean wave drag and a simple treatment of ocean surface stress redistribution within the ice via a viscous ice rheology. I find that in certain stratification regimes, inclusion of internal wave effects significantly alters ice-velocity and ice-ocean stress with implications for the freshwater content of the gyre. I also explore how seasonal variations in ice cover impact the water mass properties of the Southern Ocean. A 1D ice-ocean model is adapted and compared to oceanographic float observations in the Antarctic seasonal ice zone. I find that Ekman upwelling has a leading order impact on the seasonal evolution of the upper ocean water masses and stratification. Thesis Antarc* Antarctic Arctic Sea ice Southern Ocean ORA - Oxford University Research Archive Antarctic Arctic Southern Ocean The Antarctic |
institution |
Open Polar |
collection |
ORA - Oxford University Research Archive |
op_collection_id |
ftuloxford |
language |
English |
description |
The polar oceans are currently experiencing significant changes. Arctic and Antarctic sea ice extent and volume are changing, with a poorly constrained implication for future climate. Understanding the interactions between sea ice and the underlying ocean is fundamental for understanding current changes, and predicting future ice-states. In this thesis I study several aspects of the under-ice boundary layer and the coupling to the deeper polar ocean. First, I conduct numerical simulations of fluid flow using the Lattice Boltzmann Method to investigate the effects of stratification and roughness on ice-ocean drag and heat flux below a ridged ice floe overlaying a stably stratified ocean. It is found that sea ice generated internal waves can cause order of magnitude variations in the simulated drag coefficient and modest variations in area-integrated heatflux and its spatial distribution. A parameterization is developed for wave drag as a scaling law in terms of upper ocean velocity, stratification, and ridge geometry. To understand the potential impact, this parameterization is applied to an idealized conceptual model of an ice-covered ocean gyre. The model extends previous descriptions of ocean density variation subject to applied wind stress to account for ice-ocean wave drag and a simple treatment of ocean surface stress redistribution within the ice via a viscous ice rheology. I find that in certain stratification regimes, inclusion of internal wave effects significantly alters ice-velocity and ice-ocean stress with implications for the freshwater content of the gyre. I also explore how seasonal variations in ice cover impact the water mass properties of the Southern Ocean. A 1D ice-ocean model is adapted and compared to oceanographic float observations in the Antarctic seasonal ice zone. I find that Ekman upwelling has a leading order impact on the seasonal evolution of the upper ocean water masses and stratification. |
author2 |
Wells, A |
format |
Thesis |
author |
Thielen, K |
spellingShingle |
Thielen, K Sea ice effects on the upper ocean: internal waves, ice-covered gyres and the seasonal ice zone |
author_facet |
Thielen, K |
author_sort |
Thielen, K |
title |
Sea ice effects on the upper ocean: internal waves, ice-covered gyres and the seasonal ice zone |
title_short |
Sea ice effects on the upper ocean: internal waves, ice-covered gyres and the seasonal ice zone |
title_full |
Sea ice effects on the upper ocean: internal waves, ice-covered gyres and the seasonal ice zone |
title_fullStr |
Sea ice effects on the upper ocean: internal waves, ice-covered gyres and the seasonal ice zone |
title_full_unstemmed |
Sea ice effects on the upper ocean: internal waves, ice-covered gyres and the seasonal ice zone |
title_sort |
sea ice effects on the upper ocean: internal waves, ice-covered gyres and the seasonal ice zone |
publishDate |
2021 |
url |
https://ora.ox.ac.uk/objects/uuid:6764666b-92ef-41fa-890f-0d810cc2bade |
geographic |
Antarctic Arctic Southern Ocean The Antarctic |
geographic_facet |
Antarctic Arctic Southern Ocean The Antarctic |
genre |
Antarc* Antarctic Arctic Sea ice Southern Ocean |
genre_facet |
Antarc* Antarctic Arctic Sea ice Southern Ocean |
op_relation |
https://ora.ox.ac.uk/objects/uuid:6764666b-92ef-41fa-890f-0d810cc2bade |
op_rights |
info:eu-repo/semantics/openAccess CC Attribution (CC BY) |
op_rightsnorm |
CC-BY |
_version_ |
1766269174917627904 |