scholarly journals Impact of variable physical conditions and future increased aquaculture production on lice infestation pressure and its sustainability in Norway

2020 ◽  
Vol 12 ◽  
pp. 193-204
Author(s):  
MS Myksvoll ◽  
AD Sandvik ◽  
IA Johnsen ◽  
J Skarðhamar ◽  
J Albretsen
Keyword(s):  
Interannual Variability ◽  
Ocean Circulation ◽  
Ocean Model ◽  
Migration Route ◽  
Traffic Light ◽  
Physical Conditions ◽  
Salmon Lice ◽  
The Impact ◽  
Production Zone ◽  
Lice Infestations

Salmon lice infestation is a challenge for wild post-smolt salmon during migration from their natal river to the sea in several regions of Norway. The traffic-light management system regulates growth in the aquaculture industry, where growth in production (6%) is only allowed if the impact of salmon lice on wild fish can be kept at a minimum and up to 10% mortality of wild salmonids are considered within the sustainability goal. We used a numerical ocean model, combined with an individual-based model for salmon lice, to evaluate the interannual variability in salmon lice concentrations in Production Zone 7, which was granted permission for production growth in 2017. Salmon lice releases were kept constant for 3 yr, while the physical conditions, e.g. wind and ocean circulation, varied. The total area of elevated lice infestations varied between 3.2 and 8.4% of the area within 5 km from the coast, due only to interannual physical variability mainly caused by variable wind patterns. Modeled post-smolts migrating out from the Namsen River (64.5°N, central Norway) towards the open ocean experienced mortality between 5 and 9%. Since Production Zone 7 was granted growth, we have simulated increased production and corresponding increases in lice releases. After 5 to 8 increments of 6% increase in production, the increase in salmon post-smolt mortality was of the same order of magnitude as the interannual variability. Information regarding migration route and time is crucial input to the model calculating post-smolt mortality, and inadequate information can affect the results significantly. These 2 methods (determining area of elevated lice infestations and estimating post-smolt mortality) provide complementary information and should be used in combination when the overall assessment of a production zone is made.

scholarly journals Dynamic Downscaling of the Impact of Climate Change on the Ocean Circulation in the Galápagos Archipelago

2013 ◽  
Vol 2013 ◽  
pp. 1-18 ◽  
Author(s):  
Yanyun Liu ◽  
Lian Xie ◽  
John M. Morrison ◽  
Daniel Kamykowski
Keyword(s):  
Climate Change ◽  
Ocean Circulation ◽  
Global Climate Change ◽  
Climate Model ◽  
Global Climate ◽  
Ocean Model ◽  
Reanalysis Dataset ◽  
Equatorial Undercurrent ◽  
Galapagos Archipelago ◽  
The Impact

The regional impact of global climate change on the ocean circulation around the Galápagos Archipelago is studied using the Hybrid Coordinate Ocean Model (HYCOM) configured for a four-level nested domain system. The modeling system is validated and calibrated using daily atmospheric forcing derived from the NCEP/NCAR reanalysis dataset from 1951 to 2007. The potential impact of future anthropogenic global warming (AGW) in the Galápagos region is examined using the calibrated HYCOM with forcing derived from the IPCC-AR4 climate model. Results show that although the oceanic variability in the entire Galápagos region is significantly affected by global climate change, the degree of such effects is inhomogeneous across the region. The upwelling region to the west of the Isabella Island shows relatively slower warming trends compared to the eastern Galápagos region. Diagnostic analysis suggests that the variability in the western Galápagos upwelling region is affected mainly by equatorial undercurrent (EUC) and Panama currents, while the central/east Galápagos is predominantly affected by both Peru and EUC currents. The inhomogeneous responses in different regions of the Galápagos Archipelago to future AGW can be explained by the incoherent changes of the various current systems in the Galápagos region as a result of global climate change.

scholarly journals An Intrinsic Mode of Interannual Variability in the Indian Ocean

2017 ◽  
Vol 47 (3) ◽  
pp. 701-719 ◽  
Author(s):  
Christopher L. Wolfe ◽  
Paola Cessi ◽  
Bruce D. Cornuelle
Keyword(s):  
Indian Ocean ◽  
Interannual Variability ◽  
Ocean Circulation ◽  
Baroclinic Instability ◽  
Ocean Model ◽  
South Atlantic ◽  
Global Ocean ◽  
Leeuwin Current ◽  
The Indian Ocean ◽  
Atmospheric State

AbstractAn intrinsic mode of self-sustained, interannual variability is identified in a coarse-resolution ocean model forced by an annually repeating atmospheric state. The variability has maximum loading in the Indian Ocean, with a significant projection into the South Atlantic Ocean. It is argued that this intrinsic mode is caused by baroclinic instability of the model’s Leeuwin Current, which radiates out to the tropical Indian and South Atlantic Oceans as long Rossby waves at a period of 4 yr. This previously undescribed mode has a remarkably narrowband time series. However, the variability is not synchronized with the annual cycle; the phase of the oscillation varies chaotically on decadal time scales. The presence of this internal mode reduces the predictability of the ocean circulation by obscuring the response to forcing or initial condition perturbations. The signature of this mode can be seen in higher-resolution global ocean models driven by high-frequency atmospheric forcing, but altimeter and assimilation analyses do not show obvious signatures of such a mode, perhaps because of insufficient duration.

scholarly journals On The Interannual Variability Of A Diagnostic Ice-Ocean Model

1990 ◽  
Vol 14 ◽  
pp. 339-339
Author(s):  
W.D Hibler ◽  
Peter Ranelli
Keyword(s):  
Sea Ice ◽  
Interannual Variability ◽  
Ocean Circulation ◽  
Model Simulation ◽  
Coupled Model ◽  
Ocean Model ◽  
The Arctic ◽  
Time Interval ◽  
Ice Drift ◽  
Ice Model

Sea-ice drift and dynamics can significantly affect the exchanges of heat between the atmosphere and ocean and salt fluxes into the ocean. The ice drift and dynamics, in turn, can be modified by the ocean circulation. This is especially true of the ice margin location whose seasonal characteristics are largely controlled by the substantial oceanic heat flux in the Greenland Sea due to convective overturning.A useful framework to analyze the interannual variability of ice–ocean interaction effects relevant to climatic change is the diagnostic ice–ocean model developed by Hibler and Bryan (1987). In this model, the oceanic temperature and salinity is weakly relaxed (except in the upper layer of the ocean which is essentially driven by the ice dynamic-thermodynamic sea-ice model) to climatological temperature and salinity data. This procedure allows seasonal and interannual variability to be simulated while still preventing the baroclinic characteristics of the ocean circulation from gradually drifting off into a total model defined state. However, in the work of Hibler and Bryan only the seasonal equilibrium characteristics of this model with the same forcing repeated year after year have been considered.In order to begin to examine the interannual behavior of this model, we have carried out a three-year simulation for the Arctic Greenland and Norwegian seas over the time period 1981–83. (The geographical region is essentially the same as used by Hibler and Bryan.) This three year simulation is carried out after an initial two year spin up using the 1981 atmospheric forcing data. For comparison purposes, an ice model simulation with only a fixed depth mixed layer was also carried out over this time interval.The results of these two simulations are analyzed with special attention to the ice margin characteristics in the Greenland and Norwegian seas to determine the role of ocean circulation on the variability there. The ice margin results are also compared to the variability in the northward transports of heat through the Faero-Shetland passage which in the fully-coupled model are calculated rather than specified.

scholarly journals A nested Atlantic-Mediterranean Sea general circulation model for operational forecasting

Ocean Science ◽  
2009 ◽  
Vol 5 (4) ◽  
pp. 461-473 ◽  
Author(s):  
P. Oddo ◽  
M. Adani ◽  
N. Pinardi ◽  
C. Fratianni ◽  
M. Tonani ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
General Circulation Model ◽  
Ocean Circulation ◽  
General Circulation ◽  
Circulation Model ◽  
Ocean Model ◽  
Global Ocean ◽  
Lateral Boundary ◽  
The Mediterranean ◽  
The Impact

Abstract. A new numerical general circulation ocean model for the Mediterranean Sea has been implemented nested within an Atlantic general circulation model within the framework of the Marine Environment and Security for the European Area project (MERSEA, Desaubies, 2006). A 4-year twin experiment was carried out from January 2004 to December 2007 with two different models to evaluate the impact on the Mediterranean Sea circulation of open lateral boundary conditions in the Atlantic Ocean. One model considers a closed lateral boundary in a large Atlantic box and the other is nested in the same box in a global ocean circulation model. Impact was observed comparing the two simulations with independent observations: ARGO for temperature and salinity profiles and tide gauges and along-track satellite observations for the sea surface height. The improvement in the nested Atlantic-Mediterranean model with respect to the closed one is particularly evident in the salinity characteristics of the Modified Atlantic Water and in the Mediterranean sea level seasonal variability.

scholarly journals Impacts of the Madden–Julian Oscillation on the Summer South China Sea Ocean Circulation and Temperature

2013 ◽  
Vol 26 (20) ◽  
pp. 8084-8096 ◽  
Author(s):  
Guihua Wang ◽  
Zheng Ling ◽  
Renguang Wu ◽  
Changlin Chen
Keyword(s):  
South China Sea ◽  
Ocean Circulation ◽  
South China ◽  
Ocean Model ◽  
Ocean Modeling ◽  
Madden Julian Oscillation ◽  
Regional Ocean Modeling System ◽  
Wind Stress Curl ◽  
China Sea ◽  
The Impact

Abstract The present study investigates the impact of the Madden–Julian oscillation (MJO) on the South China Sea (SCS) in summer with three types of models: a theoretical Sverdrup model, a 1.5-layer reduced gravity model, and a regional ocean model [Regional Ocean Modeling System (ROMS)]. Results show that the ocean circulation in the SCS has an intraseasonal oscillation responding to the MJO. During its westerly phase, the MJO produces positive (negative) wind stress curl over the northern (southern) SCS and thus induces an enhanced cyclonic (anticyclonic) circulation in the northern (southern) SCS. This not only cools sea surface temperature (SST) but also decreases (increases) subsurface temperature in the northern (southern) SCS. During its easterly phase, the MJO basically produces a reversed but weaker influence on SCS ocean circulation and temperature. Thus, the MJO can have an imprint on the summer climatology of SCS circulation and temperature. The authors' analysis further indicates that the MJO's dynamic effect associated with wind is generally more important than its thermodynamic effect in modulating the regional ocean circulation and temperature. The present study suggests that the MJO is important for summer ocean circulation and temperature in the SCS.

scholarly journals On The Interannual Variability Of A Diagnostic Ice-Ocean Model

1990 ◽  
Vol 14 ◽  
pp. 339
Author(s):  
W.D Hibler ◽  
Peter Ranelli
Keyword(s):  
Sea Ice ◽  
Interannual Variability ◽  
Ocean Circulation ◽  
Model Simulation ◽  
Coupled Model ◽  
Ocean Model ◽  
The Arctic ◽  
Time Interval ◽  
Ice Drift ◽  
Ice Model

Sea-ice drift and dynamics can significantly affect the exchanges of heat between the atmosphere and ocean and salt fluxes into the ocean. The ice drift and dynamics, in turn, can be modified by the ocean circulation. This is especially true of the ice margin location whose seasonal characteristics are largely controlled by the substantial oceanic heat flux in the Greenland Sea due to convective overturning. A useful framework to analyze the interannual variability of ice–ocean interaction effects relevant to climatic change is the diagnostic ice–ocean model developed by Hibler and Bryan (1987). In this model, the oceanic temperature and salinity is weakly relaxed (except in the upper layer of the ocean which is essentially driven by the ice dynamic-thermodynamic sea-ice model) to climatological temperature and salinity data. This procedure allows seasonal and interannual variability to be simulated while still preventing the baroclinic characteristics of the ocean circulation from gradually drifting off into a total model defined state. However, in the work of Hibler and Bryan only the seasonal equilibrium characteristics of this model with the same forcing repeated year after year have been considered. In order to begin to examine the interannual behavior of this model, we have carried out a three-year simulation for the Arctic Greenland and Norwegian seas over the time period 1981–83. (The geographical region is essentially the same as used by Hibler and Bryan.) This three year simulation is carried out after an initial two year spin up using the 1981 atmospheric forcing data. For comparison purposes, an ice model simulation with only a fixed depth mixed layer was also carried out over this time interval. The results of these two simulations are analyzed with special attention to the ice margin characteristics in the Greenland and Norwegian seas to determine the role of ocean circulation on the variability there. The ice margin results are also compared to the variability in the northward transports of heat through the Faero-Shetland passage which in the fully-coupled model are calculated rather than specified.

scholarly journals Computing marine-ice thickness at an ice-shelf base

2002 ◽  
Vol 48 (160) ◽  
pp. 9-19 ◽  
Author(s):  
David M. Holland
Keyword(s):  
Numerical Method ◽  
Ocean Circulation ◽  
Sea Water ◽  
Model Simulation ◽  
Accumulation Rate ◽  
Ocean Model ◽  
Ice Thickness ◽  
Ice Shelf ◽  
The Impact ◽  
Shelf Flow

AbstractThe freezing of sea water to the base of an ice shelf can give rise to large patches of accumulated ice, a phenomenon known as marine ice. In this study a numerical method is presented for calculating the thickness of the marine-ice layer using an ice- shelf-ocean model. The present-day modeling paradigm of ice-shelf–ocean interaction usually involves the fixed specification of the ice-shelf geometry while the ocean circulation in the cavity beneath the ice shelf evolves freely. This approach relies on several assumptions, such as steady-state ice-shelf thickness and ice-shelf flow fields, in order to make reasonable quantitative estimates of the thermodynamic exchange processes occurring at the ice-shelf base. This paper discusses the impact of these and other assumptions on the estimation of the thickness of the marine-ice layer. Model simulation results are presented for an idealized ice-shelf–ocean configuration as a demonstration of the feasibility of the numerical method. A sensitivity analysis is given so as to quantify the relative uncertainty in the marine-ice thickness that arises from uncertainties in the model input parameters, these being principally the ice-shelf flow field, the basal accumulation rate and the ice-shelf thickness field.

scholarly journals Ice sheet response to sub-shelf melt rates in coupled and uncoupled peri-Antarctic ice-sheet model simulations

2021 ◽  
Author(s):  
Lars Zipf ◽  
Charles Pelletier ◽  
Konstanze Haubner ◽  
Sainan Sun ◽  
Frank Pattyn
Keyword(s):  
Ocean Circulation ◽  
Ice Sheet ◽  
Ocean Model ◽  
Ice Shelf ◽  
Ice Dynamics ◽  
Antarctic Ice Sheet ◽  
Main Driver ◽  
First Results ◽  
The Impact ◽  
Ice Model

<p>Sub-shelf melting is the main driver of Antarctica's ice sheet mass loss. However, sub-shelf melt rate parameterizations for standalone ice models lack the capability to capture complex ocean circulation within ice shelf cavities. To overcome drawbacks of standalone models and to improve melt parameterizations, high resolution coupling of ice sheet and ocean models are capable of hindcasting past decennia and be compared to observations.</p><p>Here, we present first results of a hindcast (1985-2018) of the new circumpolar coupled Southern Ocean – Antarctic ice sheet configuration, developed within the framework of the PARAMOUR project. The configuration is based on the ocean and sea ice model NEMO3.6-LIM3 and the ice sheet model f.ETISh v1.7. The coupling routine facilitates exchange of monthly sub-shelf melt rates (from ocean to ice model) and evolving ice shelf cavity geometry (from ice to ocean model).</p><p>We investigate the impact of the coupling frequency (more precisely, the frequency of updating the ice shelf cavity geometry within the ocean model) on the sub-shelf melt rates and its feedback on the ice dynamics. We further compare the sub-shelf melt rates of the coupled setup to those of the standalone ice sheet model with different sub-shelf melt rate parametrizations (ISMIP6, plume, PICO, PICOP) and investigate the sensitivity of the response of the ice sheet for the different basal melt rate patterns on decadal time scales.</p>

scholarly journals A nested Atlantic-Mediterranean Sea general circulation model for operational forecasting

2009 ◽  
Vol 6 (2) ◽  
pp. 1093-1127 ◽  
Author(s):  
P. Oddo ◽  
M. Adani ◽  
N. Pinardi ◽  
C. Fratianni ◽  
M. Tonani ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
General Circulation Model ◽  
Ocean Circulation ◽  
General Circulation ◽  
Circulation Model ◽  
Ocean Model ◽  
Global Ocean ◽  
Lateral Boundary ◽  
The Mediterranean ◽  
The Impact

Abstract. A new numerical general circulation ocean model for the Mediterranean Sea has been implemented nested within an Atlantic general circulation model within the framework of the Marine Environment and Security for the European Area project (MERSEA, Desaubies, 2006). A 4-year twin experiment was carried out from January 2004 to December 2007 with two different models to evaluate the impact on the Mediterranean Sea circulation of open lateral boundary conditions in the Atlantic Ocean. One model considers a closed lateral boundary in a large Atlantic box and the other is nested in the same box in a global ocean circulation model. Impact was observed comparing the two simulations with independent observations: ARGO for temperature and salinity profiles and tide gauges and along-track satellite observations for the sea surface height. The improvement in the nested Atlantic-Mediterranean model with respect to the closed one is particularly evident in the salinity characteristics of the Modified Atlantic Water and in the Mediterranean sea level seasonal variability.

scholarly journals Impact of combining GRACE and GOCE gravity data on ocean circulation estimates

2011 ◽  
Vol 8 (3) ◽  
pp. 1535-1573
Author(s):  
T. Janjić ◽  
J. Schröter ◽  
R. Savcenko ◽  
W. Bosch ◽  
A. Albertella ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Gravity Data ◽  
Ocean Model ◽  
Sea Surface ◽  
Altimeter Data ◽  
Argo Data ◽  
Gravity Field Model ◽  
Gravity Fields ◽  
Ocean Topography ◽  
The Impact

Abstract. In this work we examine the impact of assimilation of multi-mission-altimeter data and the GRACE/GOCE gravity fields into the finite element ocean model (FEOM), with the focus on the Southern Ocean circulation. In order to do so, we use the geodetic approach for obtaining the dynamical ocean topography (DOT), that combines the multi-mission-altimeter data and the GRACE/GOCE gravity fields, and requires that both fields be spectrally consistent. The spectral consistency is achieved by filtering of the sea surface height and the geoid using profile approach. Combining the GRACE and GOCE data, a considerably shorter filter length resolving more DOT details can be used. In order to specify the spectrally consistent geodetic DOT we applied the Jekeli-Wahr filter corresponding to 241 km, 121 km, 97 km and 81 km halfwidths for the GRACE/GOCE based gravity field model GOCO01S and to the sea surface. More realistic features of the ocean assimilation were obtained in the Weddel gyre area due to increased resolution of the data fields, particularly for temperature field at the 800 m depth compared to Argo data.

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