scholarly journals Sustaining observations in the polar oceans

2014 ◽  
Vol 372 (2025) ◽  
pp. 20130337 ◽  
Author(s):  
E. P. Abrahamsen
Keyword(s):  
Sea Ice ◽  
Ocean Circulation ◽  
Ice Cover ◽  
Global Ocean ◽  
Shelf Seas ◽  
Polar Oceans ◽  
Global Ocean Circulation ◽  
Coordination And Collaboration ◽  
Temperature Depth

Polar oceans present a unique set of challenges to sustained observations. Sea ice cover restricts navigation for ships and autonomous measurement platforms alike, and icebergs present a hazard to instruments deployed in the upper ocean and in shelf seas. However, the important role of the poles in the global ocean circulation provides ample justification for sustained observations in these regions, both to monitor the rapid changes taking place, and to better understand climate processes in these traditionally poorly sampled areas. In the past, the vast majority of polar measurements took place in the summer. In recent years, novel techniques such as miniature CTD (conductivity–temperature–depth) tags carried by seals have provided an explosion in year-round measurements in areas largely inaccessible to ships, and, as ice avoidance is added to autonomous profiling floats and gliders, these promise to provide further enhancements to observing systems. In addition, remote sensing provides vital information about changes taking place in sea ice cover at both poles. To make these observations sustainable into the future, improved international coordination and collaboration is necessary to gain optimum utilization of observing networks.

The Role of Mesoscale Tracer Transports in the Global Ocean Circulation

Science ◽  
1994 ◽  
Vol 264 (5162) ◽  
pp. 1123-1126 ◽  
Author(s):  
G. Danabasoglu ◽  
J. C. McWilliams ◽  
P. R. Gent
Keyword(s):  
Ocean Circulation ◽  
Global Ocean ◽  
Global Ocean Circulation

scholarly journals Ocean-sea-ice coupling in a global ocean general circulation model

1997 ◽  
Vol 25 ◽  
pp. 116-120 ◽  
Author(s):  
S. Legutke ◽  
E. Maier-Reimkr ◽  
A. Stössel ◽  
A. Hellbach
Keyword(s):  
Sea Ice ◽  
General Circulation Model ◽  
Ocean Circulation ◽  
General Circulation ◽  
Circulation Model ◽  
Ice Cover ◽  
Ocean General Circulation Model ◽  
Global Ocean ◽  
Ocean General Circulation ◽  
The Impact

A global ocean general circulation model has been coupled with a dynamic thermodynamic sea-ice model. This model has been spun-up in a 1000 year integration using daily atmosphere model data. Main water masses and currents are reproduced as well as the seasonal characteristics of the ice cover of the Northern and Southern Hemispheres. Model results for the Southern Ocean, however, show the ice cover as too thin, and there are large permanent polynyas in the Weddell and Ross Seas. These polynyas are due to a large upward oceanic heat flux caused by haline rejection during the freezing of sea ice. Sensitivity studies were performed to test several ways of treating the sea-surface salinity and the rejected brine. The impact on the ice cover, water-mass characteristics, and ocean circulation are described.

scholarly journals Ocean-sea-ice coupling in a global ocean general circulation model

1997 ◽  
Vol 25 ◽  
pp. 116-120 ◽  
Author(s):  
S. Legutke ◽  
E. Maier-Reimkr ◽  
A. Stössel ◽  
A. Hellbach
Keyword(s):  
Sea Ice ◽  
General Circulation Model ◽  
Ocean Circulation ◽  
General Circulation ◽  
Circulation Model ◽  
Ice Cover ◽  
Ocean General Circulation Model ◽  
Global Ocean ◽  
Ocean General Circulation ◽  
The Impact

A global ocean general circulation model has been coupled with a dynamic thermodynamic sea-ice model. This model has been spun-up in a 1000 year integration using daily atmosphere model data. Main water masses and currents are reproduced as well as the seasonal characteristics of the ice cover of the Northern and Southern Hemispheres. Model results for the Southern Ocean, however, show the ice cover as too thin, and there are large permanent polynyas in the Weddell and Ross Seas. These polynyas are due to a large upward oceanic heat flux caused by haline rejection during the freezing of sea ice. Sensitivity studies were performed to test several ways of treating the sea-surface salinity and the rejected brine. The impact on the ice cover, water-mass characteristics, and ocean circulation are described.

scholarly journals Arctic Mediterranean Exchanges: A consistent volume budget and trends in transports from two decades of observations

2020 ◽  
Author(s):  
Svein Østerhus ◽  
Rebecca Woodgate ◽  
Héðinn Valdimarsson ◽  
Bill Turrell ◽  
Laura de Steur ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Integrated Assessment ◽  
Volume Transport ◽  
The Arctic ◽  
Global Ocean ◽  
Lower Latitude ◽  
Bering Strait ◽  
Transport Time ◽  
Shelf Seas ◽  
Global Ocean Circulation

<p>Conditions in the Arctic are in part driven by the ocean state in the Arctic Mediterranean (AM), the collective name for the Arctic Ocean, the Nordic Seas, and their adjacent shelf seas. Exchange between the lower latitude ocean basins and this region occurs through the Bering Strait (Pacific inflow) and through the passages across the Greenland-Scotland Ridge (Atlantic inflow). These waters are subsequently modified within the AM. The modified waters leave the AM in several flow branches, which are grouped into two different categories: (1) overflow of dense water through the deep passages across the Greenland-Scotland Ridge, and (2) outflow of light water (surface outflow) on both sides of Greenland. These exchanges transport heat and salt into and out of the AM and are important for conditions in the AM. They are also part of the global ocean circulation and climate system. Attempts to quantify the transports by various methods have been made for many years, but only recently, the observational coverage has become sufficiently complete to allow an integrated assessment of the AM-exchanges based solely on observations.</p><p>In this EGU contribution, we focus on the observations (incl. volume transport time series) of all the main AM-exchange branches collected in the last 20 to 30 years.</p>

On the impact of sea ice in a global ocean circulation model

1997 ◽  
Vol 25 ◽  
pp. 111-115 ◽  
Author(s):  
Achim Stössel
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Ocean Circulation ◽  
General Circulation ◽  
Thermohaline Circulation ◽  
Circulation Model ◽  
Deep Ocean ◽  
Global Ocean ◽  
Convective Activity ◽  
The Impact

This paper investigates the long-term impact of sea ice on global climate using a global sea-ice–ocean general circulation model (OGCM). The sea-ice component involves state-of-the-art dynamics; the ocean component consists of a 3.5° × 3.5° × 11 layer primitive-equation model. Depending on the physical description of sea ice, significant changes are detected in the convective activity, in the hydrographic properties and in the thermohaline circulation of the ocean model. Most of these changes originate in the Southern Ocean, emphasizing the crucial role of sea ice in this marginally stably stratified region of the world's oceans. Specifically, if the effect of brine release is neglected, the deep layers of the Southern Ocean warm up considerably; this is associated with a weakening of the Southern Hemisphere overturning cell. The removal of the commonly used “salinity enhancement” leads to a similar effect. The deep-ocean salinity is almost unaffected in both experiments. Introducing explicit new-ice thickness growth in partially ice-covered gridcells leads to a substantial increase in convective activity, especially in the Southern Ocean, with a concomitant significant cooling and salinification of the deep ocean. Possible mechanisms for the resulting interactions between sea-ice processes and deep-ocean characteristics are suggested.

scholarly journals Double-diffusive mixing makes a small contribution to the global ocean circulation

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Carine G. van der Boog ◽  
Henk A. Dijkstra ◽  
Julie D. Pietrzak ◽  
Caroline A. Katsman
Keyword(s):  
Ocean Circulation ◽  
Mechanical Energy ◽  
Global Ocean ◽  
Small Contribution ◽  
Global Ocean Circulation ◽  
Diffusive Fluxes ◽  
Diffusive Mixing ◽  
Diffusive Processes ◽  
Flowing Waters ◽  
Double Diffusive

AbstractDouble-diffusive processes enhance diapycnal mixing of heat and salt in the open ocean. However, observationally based evidence of the effects of double-diffusive mixing on the global ocean circulation is lacking. Here we analyze the occurrence of double-diffusive thermohaline staircases in a dataset containing over 480,000 temperature and salinity profiles from Argo floats and Ice-Tethered Profilers. We show that about 14% of all profiles contains thermohaline staircases that appear clustered in specific regions, with one hitherto unknown cluster overlying the westward flowing waters of the Tasman Leakage. We estimate the combined contribution of double-diffusive fluxes in all thermohaline staircases to the global ocean’s mechanical energy budget as 7.5 GW [0.1 GW; 32.8 GW]. This is small compared to the estimated energy required to maintain the observed ocean stratification of roughly 2 TW. Nevertheless, we suggest that the regional effects, for example near Australia, could be pronounced.

The Role of Oscillating Southern Hemisphere Westerly Winds: Global Ocean Circulation

2020 ◽  
Vol 33 (6) ◽  
pp. 2111-2130
Author(s):  
Woo Geun Cheon ◽  
Jong-Seong Kug
Keyword(s):  
Ocean Circulation ◽  
North Atlantic ◽  
North Pacific ◽  
Global Ocean ◽  
The North ◽  
Westerly Winds ◽  
The North Atlantic ◽  
Global Ocean Circulation ◽  
The Antarctic ◽  
The North Pacific

AbstractIn the framework of a sea ice–ocean general circulation model coupled to an energy balance atmospheric model, an intensity oscillation of Southern Hemisphere (SH) westerly winds affects the global ocean circulation via not only the buoyancy-driven teleconnection (BDT) mode but also the Ekman-driven teleconnection (EDT) mode. The BDT mode is activated by the SH air–sea ice–ocean interactions such as polynyas and oceanic convection. The ensuing variation in the Antarctic meridional overturning circulation (MOC) that is indicative of the Antarctic Bottom Water (AABW) formation exerts a significant influence on the abyssal circulation of the globe, particularly the Pacific. This controls the bipolar seesaw balance between deep and bottom waters at the equator. The EDT mode controlled by northward Ekman transport under the oscillating SH westerly winds generates a signal that propagates northward along the upper ocean and passes through the equator. The variation in the western boundary current (WBC) is much stronger in the North Atlantic than in the North Pacific, which appears to be associated with the relatively strong and persistent Mindanao Current (i.e., the southward flowing WBC of the North Pacific tropical gyre). The North Atlantic Deep Water (NADW) formation is controlled by salt advected northward by the North Atlantic WBC.

scholarly journals Impact of partial steps and momentum advection schemes in a global ocean circulation model at eddy-permitting resolution

2006 ◽  
Vol 56 (5-6) ◽  
pp. 543-567 ◽  
Author(s):  
Barnier Bernard ◽  
Gurvan Madec ◽  
Thierry Penduff ◽  
Jean-Marc Molines ◽  
Anne-Marie Treguier ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Circulation Model ◽  
Global Ocean ◽  
Ocean Circulation Model ◽  
Advection Schemes ◽  
Global Ocean Circulation

scholarly journals Viscosity and elasticity: a model intercomparison of ice-shelf bending in an Antarctic grounding zone

2017 ◽  
Vol 63 (240) ◽  
pp. 573-580 ◽  
Author(s):  
CHRISTIAN T. WILD ◽  
OLIVER J. MARSH ◽  
WOLFGANG RACK
Keyword(s):  
Young’S Modulus ◽  
Ocean Circulation ◽  
Young's Modulus ◽  
Viscoelastic Model ◽  
Ice Sheet ◽  
Global Ocean ◽  
Elastic Model ◽  
Ice Shelf ◽  
Bending Stresses ◽  
Global Ocean Circulation

ABSTRACTGrounding zones are vital to ice-sheet mass balance and its coupling to the global ocean circulation. Processes here determine the mass discharge from the grounded ice sheet, to the floating ice shelves. The response of this transition zone to tidal forcing has been described by both elastic and viscoelastic models. Here we examine the validity of these models for grounding zone flexure over tidal timescales using field data from the Southern McMurdo Ice Shelf (78° 15′S, 167° 7′E). Observations of tidal movement were carried out by simultaneous tiltmeter and GPS measurements along a profile across the grounding zone. Finite-element simulations covering a 64 d period reveal that the viscoelastic model fits best the observations using a Young's modulus of 1.6 GPa and a viscosity of 1013.7 Pa s (≈ 50.1 TPa s). We conclude that the elastic model is only well-constrained for tidal displacements >35% of the spring-tidal amplitude using a Young's modulus of 1.62 ± 0.69 GPa, but that a viscoelastic model is necessary to adequately capture tidal bending at amplitudes below this threshold. In grounding zones where bending stresses are greater than at the Southern McMurdo Ice Shelf or ice viscosity is lower, the threshold would be even higher.

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