Future Changes in Oceanography and Biogeochemistry Along the Canadian Pacific Continental Margin

Model projections of ocean circulation and biogeochemistry are used to investigate large scale climate changes under moderate mitigation (RCP 4.5) and high emissions (RCP 8.5) scenarios along the continental shelf of the Canadian Pacific Coast. To reduce computational cost, an approach for dynamical...

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Main Authors: Amber M. Holdsworth, Li Zhai, Youyu Lu, James R. Christian
Format: Article
Language:English
Published: Frontiers Media S.A. 2021-03-01
Series:Frontiers in Marine Science
Subjects:
Online Access:https://www.frontiersin.org/articles/10.3389/fmars.2021.602991/full
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author Amber M. Holdsworth
Li Zhai
Youyu Lu
James R. Christian
James R. Christian
author_facet Amber M. Holdsworth
Li Zhai
Youyu Lu
James R. Christian
James R. Christian
author_sort Amber M. Holdsworth
collection DOAJ
description Model projections of ocean circulation and biogeochemistry are used to investigate large scale climate changes under moderate mitigation (RCP 4.5) and high emissions (RCP 8.5) scenarios along the continental shelf of the Canadian Pacific Coast. To reduce computational cost, an approach for dynamical downscaling of climate projections was developed that uses atmospheric climatologies with augmented winds to simulate historical (1986–2005) and future (2046–2065) periods separately. The two simulations differ in initial and lateral open boundary conditions. For each simulation, the daily climatology of surface winds in the driving model was augmented with high-frequency variability from an atmospheric reanalysis product. The “time-slice” approach was able to reproduce the observed climate state for the historical period. Sensitivity tests confirmed that the high frequency wind variability plays an essential role in freshwater distribution in this region. Projections suggest that sea surface temperature will increase by 1.8–2.4°C and surface salinity will decrease between −0.08 and −0.23 depending on whether a moderate or high emissions scenario is used. Stratification increases throughout the region and there is some evidence of nutrient limitation near the surface. Primary production and phytoplankton productivity (chlorophyll) also increase. Density surfaces are relocated deeper in the water column and this change is mainly driven by surface heating and freshening. Changes in saturation state are mainly due to anthropogenic CO2 with minor contributions from solubility, remineralization and advection. There is little difference between RCP 4.5 and RCP 8.5 with regard to projections of deoxygenation and acidification. The depths of the aragonite saturation state and the oxygen minimum zone are projected to become shallower by ≃ 100 and ≃ 75 m respectively. Extreme states of temperature, oxygen and acidification are projected to become more frequent and more extreme, with the frequency of occurrence of [O2]<60 mmolm-3 expected to approximately double under either scenario.
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spelling doaj.art-46a0319fdf474be389bacb808e9fc8462022-12-21T23:02:27ZengFrontiers Media S.A.Frontiers in Marine Science2296-77452021-03-01810.3389/fmars.2021.602991602991Future Changes in Oceanography and Biogeochemistry Along the Canadian Pacific Continental MarginAmber M. Holdsworth0Li Zhai1Youyu Lu2James R. Christian3James R. Christian4Fisheries and Oceans Canada, Institute of Ocean Sciences, Sidney, BC, CanadaFisheries and Oceans Canada, Bedford Institute of Oceanography, Dartmouth, NS, CanadaFisheries and Oceans Canada, Bedford Institute of Oceanography, Dartmouth, NS, CanadaFisheries and Oceans Canada, Institute of Ocean Sciences, Sidney, BC, CanadaCanadian Centre for Climate Modelling and Analysis, Victoria, BC, CanadaModel projections of ocean circulation and biogeochemistry are used to investigate large scale climate changes under moderate mitigation (RCP 4.5) and high emissions (RCP 8.5) scenarios along the continental shelf of the Canadian Pacific Coast. To reduce computational cost, an approach for dynamical downscaling of climate projections was developed that uses atmospheric climatologies with augmented winds to simulate historical (1986–2005) and future (2046–2065) periods separately. The two simulations differ in initial and lateral open boundary conditions. For each simulation, the daily climatology of surface winds in the driving model was augmented with high-frequency variability from an atmospheric reanalysis product. The “time-slice” approach was able to reproduce the observed climate state for the historical period. Sensitivity tests confirmed that the high frequency wind variability plays an essential role in freshwater distribution in this region. Projections suggest that sea surface temperature will increase by 1.8–2.4°C and surface salinity will decrease between −0.08 and −0.23 depending on whether a moderate or high emissions scenario is used. Stratification increases throughout the region and there is some evidence of nutrient limitation near the surface. Primary production and phytoplankton productivity (chlorophyll) also increase. Density surfaces are relocated deeper in the water column and this change is mainly driven by surface heating and freshening. Changes in saturation state are mainly due to anthropogenic CO2 with minor contributions from solubility, remineralization and advection. There is little difference between RCP 4.5 and RCP 8.5 with regard to projections of deoxygenation and acidification. The depths of the aragonite saturation state and the oxygen minimum zone are projected to become shallower by ≃ 100 and ≃ 75 m respectively. Extreme states of temperature, oxygen and acidification are projected to become more frequent and more extreme, with the frequency of occurrence of [O2]<60 mmolm-3 expected to approximately double under either scenario.https://www.frontiersin.org/articles/10.3389/fmars.2021.602991/fullmodelingbiogeochemistryacidificationdeoxygenationPacific oceanprojection
spellingShingle Amber M. Holdsworth
Li Zhai
Youyu Lu
James R. Christian
James R. Christian
Future Changes in Oceanography and Biogeochemistry Along the Canadian Pacific Continental Margin
Frontiers in Marine Science
modeling
biogeochemistry
acidification
deoxygenation
Pacific ocean
projection
title Future Changes in Oceanography and Biogeochemistry Along the Canadian Pacific Continental Margin
title_full Future Changes in Oceanography and Biogeochemistry Along the Canadian Pacific Continental Margin
title_fullStr Future Changes in Oceanography and Biogeochemistry Along the Canadian Pacific Continental Margin
title_full_unstemmed Future Changes in Oceanography and Biogeochemistry Along the Canadian Pacific Continental Margin
title_short Future Changes in Oceanography and Biogeochemistry Along the Canadian Pacific Continental Margin
title_sort future changes in oceanography and biogeochemistry along the canadian pacific continental margin
topic modeling
biogeochemistry
acidification
deoxygenation
Pacific ocean
projection
url https://www.frontiersin.org/articles/10.3389/fmars.2021.602991/full
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