scholarly journals Open-ocean convection and polynya formation in a large-scale ice–ocean model

2001 ◽  
Vol 53 (1) ◽  
pp. 94-111 ◽  
Author(s):  
Hugues Goosse ◽  
Thierry Fichefet
Keyword(s):  
Large Scale ◽  
Ocean Model ◽  
Open Ocean ◽  
Ocean Convection

scholarly journals The Dynamics of Mixed Layer Deepening during Open-Ocean Convection

2020 ◽  
Vol 50 (6) ◽  
pp. 1625-1641
Author(s):  
Taimoor Sohail ◽  
Bishakhdatta Gayen ◽  
Andrew McC. Hogg
Keyword(s):  
Mixed Layer ◽  
Large Scale ◽  
Numerical Models ◽  
Mixed Layer Depth ◽  
Baroclinic Instability ◽  
Open Ocean ◽  
Scale Model ◽  
Quasi Equilibrium ◽  
Layer Depth ◽  
Ocean Convection

AbstractOpen-ocean convection is a common phenomenon that regulates mixed layer depth and ocean ventilation in the high-latitude oceans. However, many climate model simulations overestimate mixed layer depth during open-ocean convection, resulting in excessive formation of dense water in some regions. The physical processes controlling transient mixed layer depth during open-ocean convection are examined using two different numerical models: a high-resolution, turbulence-resolving nonhydrostatic model and a large-scale hydrostatic ocean model. An isolated destabilizing buoyancy flux is imposed at the surface of both models and a quasi-equilibrium flow is allowed to develop. Mixed layer depth in the turbulence-resolving and large-scale models closely aligns with existing scaling theories. However, the large-scale model has an anomalously deep mixed layer prior to quasi-equilibrium. This transient mixed layer depth bias is a consequence of the lack of resolved turbulent convection in the model, which delays the onset of baroclinic instability. These findings suggest that in order to reduce mixed layer biases in ocean simulations, parameterizations of the connection between baroclinic instability and convection need to be addressed.

scholarly journals Global Atmospheric Teleconnections and Multidecadal Climate Oscillations Driven by Southern Ocean Convection

2017 ◽  
Vol 30 (20) ◽  
pp. 8107-8126 ◽  
Author(s):  
Anna Cabré ◽  
Irina Marinov ◽  
Anand Gnanadesikan
Keyword(s):  
Southern Ocean ◽  
Time Scales ◽  
Large Scale ◽  
Climate Models ◽  
Global Climate ◽  
Critical Role ◽  
Global Scale ◽  
Ocean Model ◽  
Geophysical Fluid Dynamics Laboratory ◽  
Ocean Convection

Abstract A 1000-yr control simulation in a low-resolution coupled atmosphere–ocean model from the Geophysical Fluid Dynamics Laboratory (GFDL) family of climate models shows a natural, highly regular multidecadal oscillation between periods of Southern Ocean (SO) open-ocean convection and nonconvective periods. It is shown here that convective periods are associated with warming of the SO sea surface temperatures (SSTs), and more broadly of the Southern Hemisphere (SH) SSTs and atmospheric temperatures. This SO warming results in a decrease in the meridional gradient of SSTs in the SH, changing the large-scale pressure patterns, reducing the midlatitude baroclinicity and thus the magnitude of the southern Ferrel and Hadley cells, and weakening the SO westerly winds and the SH tropical trade winds. The rearrangement of the atmospheric circulation is consistent with the global energy balance. During convective decades, the increase in incoming top-of-the-atmosphere radiation in the SH is balanced by an increase in the Northern Hemisphere (NH) outgoing radiation. The energy supplying this increase is carried by enhanced atmospheric transport across the equator, as the intertropical convergence zone and associated wind patterns shift southward, toward the anomalously warmer SH. While the critical role of the SO for climate on long, paleoclimate time scales is now beyond debate, the strength and global scale of the teleconnections observed here also suggest an important role for the SO in global climate dynamics on the shorter interannual and multidecadal time scales.

scholarly journals Large-Scale Dynamics of Circulations with Open-Ocean Convection

2015 ◽  
Vol 45 (12) ◽  
pp. 2933-2951 ◽  
Author(s):  
Fabian Schloesser
Keyword(s):  
Ocean Circulation ◽  
Rossby Wave ◽  
Large Scale ◽  
Variable Density ◽  
Ocean Basin ◽  
Open Ocean ◽  
Western Boundary ◽  
Density Maximum ◽  
The North ◽  
Ocean Convection

AbstractFormation of the densest water masses in the North Atlantic and its marginal seas involves open-ocean convection. The main goal of this study is to contribute to the general understanding of how such convective regions connect to the large-scale ocean circulation. Specifically, analytic and numerical versions of a variable density layer model are used to explore the processes underlying the circulation in an idealized ocean basin. The models are forced by a surface buoyancy flux, which generates a density maximum in the ocean interior. In response to the forcing, a region forms that is characterized by the closed Rossby wave characteristics and where the eddy–mean transport converges toward the convective site. Outside of that region, characteristics extend from the eastern boundary and a distorted β-plume circulation develops, linking the convection site with the western boundary. The overturning strength in the model can be related to several environment variables and forcings and is constrained by the surface density field, stratification, eddy mixing strength and by Rossby wave dynamics. Solutions forced by an interior ocean density minimum are also considered. Although no convection occurs, the dynamics underlying the circulation are closely related to the case with cooling.

scholarly journals A Heton Perspective of Baroclinic Eddy Transfer in Localized Open Ocean Convection

1996 ◽  
Vol 26 (10) ◽  
pp. 2251-2266 ◽  
Author(s):  
Sonya Legg ◽  
Helen Jones ◽  
Martin Visbeck
Keyword(s):  
Open Ocean ◽  
Ocean Convection

scholarly journals Open-ocean convection: Observations, theory, and models

1999 ◽  
Vol 37 (1) ◽  
pp. 1-64 ◽  
Author(s):  
John Marshall ◽  
Friedrich Schott
Keyword(s):  
Open Ocean ◽  
Ocean Convection

Ocean Salinity Aspects of the Ningaloo Niño

2021 ◽  
pp. 1
Author(s):  
Yaru Guo ◽  
Yuanlong Li ◽  
Fan Wang ◽  
Yuntao Wei
Keyword(s):  
Fresh Water ◽  
Large Scale ◽  
Southern Oscillation ◽  
Regional Climate ◽  
Ocean Model ◽  
Sea Surface ◽  
Sea Surface Salinity ◽  
Surface Salinity ◽  
Near Surface ◽  
Ocean Salinity

AbstractNingaloo Niño – the interannually occurring warming episode in the southeast Indian Ocean (SEIO) – has strong signatures in ocean temperature and circulation and exerts profound impacts on regional climate and marine biosystems. Analysis of observational data and eddy-resolving regional ocean model simulations reveals that the Ningaloo Niño/Niña can also induce pronounced variability in ocean salinity, causing large-scale sea surface salinity (SSS) freshening of 0.15–0.20 psu in the SEIO during its warm phase. Model experiments are performed to understand the underlying processes. This SSS freshening is mutually caused by the increased local precipitation (~68%) and enhanced fresh-water transport of the Indonesian Throughflow (ITF; ~28%) during Ningaloo Niño events. The effects of other processes, such as local winds and evaporation, are secondary (~18%). The ITF enhances the southward fresh-water advection near the eastern boundary, which is critical in causing the strong freshening (> 0.20 psu) near the Western Australian coast. Owing to the strong modulation effect of the ITF, SSS near the coast bears a higher correlation with the El Niño-Southern Oscillation (0.57, 0.77, and 0.70 with Niño-3, Niño-4, and Niño-3.4 indices, respectively) than sea surface temperature (-0.27, -0.42, and -0.35) during 1993-2016. Yet, an idealized model experiment with artificial damping for salinity anomaly indicates that ocean salinity has limited impact on ocean near-surface stratification and thus minimal feedback effect on the warming of Ningaloo Niño.

scholarly journals Ocean Convection

Fluids ◽  
2021 ◽  
Vol 6 (10) ◽  
pp. 360
Author(s):  
Catherine Vreugdenhil ◽  
Bishakhdatta Gayen
Keyword(s):  
Climate Change ◽  
Ocean Circulation ◽  
Mixed Layer ◽  
Water Mass ◽  
Current Knowledge ◽  
Open Ocean ◽  
Meridional Overturning Circulation ◽  
Ocean Dynamics ◽  
Global Circulation Models ◽  
Ocean Convection

Ocean convection is a key mechanism that regulates heat uptake, water-mass transformation, CO2 exchange, and nutrient transport with crucial implications for ocean dynamics and climate change. Both cooling to the atmosphere and salinification, from evaporation or sea-ice formation, cause surface waters to become dense and down-well as turbulent convective plumes. The upper mixed layer in the ocean is significantly deepened and sustained by convection. In the tropics and subtropics, night-time cooling is a main driver of mixed layer convection, while in the mid- and high-latitude regions, winter cooling is key to mixed layer convection. Additionally, at higher latitudes, and particularly in the sub-polar North Atlantic Ocean, the extensive surface heat loss during winter drives open-ocean convection that can reach thousands of meters in depth. On the Antarctic continental shelf, polynya convection regulates the formation of dense bottom slope currents. These strong convection events help to drive the immense water-mass transport of the globally-spanning meridional overturning circulation (MOC). However, convection is often highly localised in time and space, making it extremely difficult to accurately measure in field observations. Ocean models such as global circulation models (GCMs) are unable to resolve convection and turbulence and, instead, rely on simple convective parameterizations that result in a poor representation of convective processes and their impact on ocean circulation, air–sea exchange, and ocean biology. In the past few decades there has been markedly more observations, advancements in high-resolution numerical simulations, continued innovation in laboratory experiments and improvement of theory for ocean convection. The impacts of anthropogenic climate change on ocean convection are beginning to be observed, but key questions remain regarding future climate scenarios. Here, we review the current knowledge and future direction of ocean convection arising from sea–surface interactions, with a focus on mixed layer, open-ocean, and polynya convection.

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