scholarly journals Deglacial Heat Uptake by the Southern Ocean and Rapid Northward Redistribution Via Antarctic Intermediate Water

2018 ◽  
Vol 33 (11) ◽  
pp. 1292-1305 ◽  
Author(s):  
D.‐W. Poggemann ◽  
D. Nürnberg ◽  
E. C. Hathorne ◽  
M. Frank ◽  
W. Rath ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Intermediate Water ◽  
Antarctic Intermediate Water ◽  
Heat Uptake

International southern ocean studies of circumpolar dynamics

Polar Record ◽  
1979 ◽  
Vol 19 (122) ◽  
pp. 461-471 ◽  
Author(s):  
Victor T. Neal ◽  
Worth D. Nowlin
Keyword(s):  
Southern Ocean ◽  
Scientific Community ◽  
Bottom Water ◽  
Intermediate Water ◽  
Antarctic Bottom Water ◽  
Formation Region ◽  
Antarctic Intermediate Water ◽  
Circumpolar Current ◽  
Principal Region ◽  
Ocean Studies

The Southern Ocean has unique features that have aroused the interest of the scientific community. As the site of the only circumpolar current, it is the principal region where waters from the major ocean basins may be mixed and/or interchanged. It is also the formation region for Antarctic Bottom Water and Antarctic Intermediate Water, which penetrate far northward into the major ocean basins.

scholarly journals An Exchange Window for the Injection of Antarctic Intermediate Water into the South Pacific

2007 ◽  
Vol 37 (1) ◽  
pp. 31-49 ◽  
Author(s):  
Daniele Iudicone ◽  
Keith B. Rodgers ◽  
Richard Schopp ◽  
Gurvan Madec
Keyword(s):  
Southern Ocean ◽  
Large Scale ◽  
South Pacific ◽  
Intermediate Water ◽  
The South ◽  
Antarctic Intermediate Water ◽  
South Pacific Ocean ◽  
The Pacific ◽  
Basin Scale ◽  
Circumpolar Current

Abstract Antarctic Intermediate Water (AAIW) occupies the intermediate horizon of most of the world oceans. Formed in the Southern Ocean, it is characterized by a relative salinity minimum. With a new, denser in situ National Oceanographic Data Center dataset, the authors have reanalyzed the export characteristics of AAIW from the Southern Ocean into the South Pacific Ocean. These new data show that part of the AAIW is exported from the subpolar frontal region by the large-scale circulation through an exchange window of 10° width situated east of 90°W in the southeast corner of the Pacific basin. This suggests the origin of this water to be in the Antarctic Circumpolar Current. A set of numerical modeling experiments has been used to reproduce these observed features and to demonstrate that the dynamics of the exchange window is controlled by the basin-scale meridional pressure gradient. The exchange of AAIW between the Southern and Pacific Oceans must therefore be understood in the context of the large basin-scale dynamical balance rather than simply local effects.

scholarly journals Opening the window to the Southern Ocean: The role of jet dynamics

2018 ◽  
Vol 4 (10) ◽  
pp. eaao4719 ◽  
Author(s):  
Andreas Klocker
Keyword(s):  
Southern Ocean ◽  
Mixed Layer ◽  
Global Climate ◽  
Control Valve ◽  
Intermediate Water ◽  
Surface Mixed Layer ◽  
Last Deglaciation ◽  
Antarctic Intermediate Water ◽  
Topographic Features ◽  
Ocean Ventilation

The surface waters of the Southern Ocean act as a control valve through which climatically important tracers such as heat, freshwater, and CO2 are transferred between the atmosphere and the ocean. The process that transports these tracers through the surface mixed layer into the ocean interior is known as ocean ventilation. Changes in ocean ventilation are thought to be important for both rapid transitions of the ocean’s global overturning circulation during the last deglaciation and the uptake and storage of excess heat and CO2 as a consequence of anthropogenic climate change. I show how the interaction between Southern Ocean jets, topographic features, and ocean stratification can lead to rapid changes in Southern Ocean ventilation as a function of wind stress. For increasing winds, this interaction leads from a state in which tracers are confined to the surface mixed layer to a state in which tracers fill the ocean interior. For sufficiently high winds, the jet dynamics abruptly change, allowing the tracer to ventilate a water mass known as Antarctic Intermediate Water in the mid-depth Southern Ocean. Abrupt changes in Antarctic Intermediate Water ventilation have played a major role in rapid climate transitions in Earth’s past, and combined with the results presented here, this would suggest that jet dynamics could play a prominent role in contributing to, or even triggering, rapid transitions of the global climate system.

scholarly journals Silicon isotopes in Antarctic sponges: an interlaboratory comparison

2010 ◽  
Vol 23 (1) ◽  
pp. 34-42 ◽  
Author(s):  
Katharine R. Hendry ◽  
Melanie J. Leng ◽  
Laura F. Robinson ◽  
Hilary J. Sloane ◽  
Jerzy Blusztjan ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Matrix Effects ◽  
Global Climate ◽  
Intermediate Water ◽  
Silicon Isotopes ◽  
Important Player ◽  
Si Isotopes ◽  
Si Isotope ◽  
Additional Reference ◽  
Antarctic Sponges

AbstractCycling of deepwater silicon (Si) within the Southern Ocean, and its transport into other ocean basins, may be an important player in the uptake of atmospheric carbon, and global climate. Recent work has shown that the Si isotope (denoted by δ29Si or δ30Si) composition of deep sea sponges reflects the availability of dissolved Si during growth, and is a potential proxy for past deep and intermediate water silicic acid concentrations. As with any geochemical tool, it is essential to ensure analytical precision and accuracy, and consistency between methodologies and laboratories. Analytical bias may exist between laboratories, and sponge material may have matrix effects leading to offsets between samples and standards. Here, we report an interlaboratory evaluation of Si isotopes in Antarctic and sub-Antarctic sponges. We review independent methods for measuring Si isotopes in sponge spicules. Our results show that separate subsamples of non-homogenized sponges measured by three methods yield isotopic values within analytical error for over 80% of specimens. The relationship between δ29Si and δ30Si in sponges is consistent with kinetic fractionation during biomineralization. Sponge Si isotope analyses show potential as palaeoceaongraphic archives, and we suggest Southern Ocean sponge material would form a useful additional reference standard for future spicule analyses.

scholarly journals Silicon pool dynamics and biogenic silica export in the Southern Ocean inferred from Si-isotopes

Ocean Science ◽  
2011 ◽  
Vol 7 (5) ◽  
pp. 533-547 ◽  
Author(s):  
F. Fripiat ◽  
A.-J. Cavagna ◽  
F. Dehairs ◽  
S. Speich ◽  
L. André ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Silicic Acid ◽  
Mixed Layer ◽  
Deep Water ◽  
Biogenic Silica ◽  
Polar Front ◽  
Intermediate Water ◽  
Subtropical Zone ◽  
Isotopic Signatures ◽  
The Antarctic

Abstract. Silicon isotopic signatures (δ30Si) of water column silicic acid (Si(OH)4) were measured in the Southern Ocean, along a meridional transect from South Africa (Subtropical Zone) down to 57° S (northern Weddell Gyre). This provides the first reported data of a summer transect across the whole Antarctic Circumpolar Current (ACC). δ30Si variations are large in the upper 1000 m, reflecting the effect of the silica pump superimposed upon meridional water transfer across the ACC: the transport of Antarctic surface waters northward by a net Ekman drift and their convergence and mixing with warmer upper-ocean Si-depleted waters to the north. Using Si isotopic signatures, we determine different mixing interfaces: the Antarctic Surface Water (AASW), the Antarctic Intermediate Water (AAIW), and thermoclines in the low latitude areas. The residual silicic acid concentrations of end-members control the δ30Si alteration of the mixing products and with the exception of AASW, all mixing interfaces have a highly Si-depleted mixed layer end-member. These processes deplete the silicic acid AASW concentration northward, across the different interfaces, without significantly changing the AASW δ30Si composition. By comparing our new results with a previous study in the Australian sector we show that during the circumpolar transport of the ACC eastward, the δ30Si composition of the silicic acid pools is getting slightly, but significantly lighter from the Atlantic to the Australian sectors. This results either from the dissolution of biogenic silica in the deeper layers and/or from an isopycnal mixing with the deep water masses in the different oceanic basins: North Atlantic Deep Water in the Atlantic, and Indian Ocean deep water in the Indo-Australian sector. This isotopic trend is further transmitted to the subsurface waters, representing mixing interfaces between the surface and deeper layers. Through the use of δ30Si constraints, net biogenic silica production (representative of annual export), at the Greenwich Meridian is estimated to be 5.2 ± 1.3 and 1.1 ± 0.3 mol Si m−2 for the Antarctic Zone and Polar Front Zone, respectively. This is in good agreement with previous estimations. Furthermore, summertime Si-supply into the mixed layer of both zones, via vertical mixing, is estimated to be 1.6 ± 0.4 and 0.1 ± 0.5 mol Si m−2, respectively.

Evolving Relative Importance of the Southern Ocean and North Atlantic in Anthropogenic Ocean Heat Uptake

2018 ◽  
Vol 31 (18) ◽  
pp. 7459-7479 ◽  
Author(s):  
Jia-Rui Shi ◽  
Shang-Ping Xie ◽  
Lynne D. Talley
Keyword(s):  
Southern Ocean ◽  
North Atlantic ◽  
Radiative Forcing ◽  
Meridional Overturning Circulation ◽  
Anthropogenic Heat ◽  
Anthropogenic Aerosols ◽  
Ocean Heat Uptake ◽  
The North ◽  
Heat Uptake ◽  
The North Atlantic

Ocean uptake of anthropogenic heat over the past 15 years has mostly occurred in the Southern Ocean, based on Argo float observations. This agrees with historical simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5), where the Southern Ocean (south of 30°S) accounts for 72% ± 28% of global heat uptake, while the contribution from the North Atlantic north of 30°N is only 6%. Aerosols preferentially cool the Northern Hemisphere, and the effect on surface heat flux over the subpolar North Atlantic opposes the greenhouse gas (GHG) effect in nearly equal magnitude. This heat uptake compensation is associated with weakening (strengthening) of the Atlantic meridional overturning circulation (AMOC) in response to GHG (aerosol) radiative forcing. Aerosols are projected to decline in the near future, reinforcing the greenhouse effect on the North Atlantic heat uptake. As a result, the Southern Ocean, which will continue to take up anthropogenic heat largely through the mean upwelling of water from depth, will be joined by increased relative contribution from the North Atlantic because of substantial AMOC slowdown in the twenty-first century. In the RCP8.5 scenario, the percentage contribution to global uptake is projected to decrease to 48% ± 8% in the Southern Ocean and increase to 26% ± 6% in the northern North Atlantic. Despite the large uncertainty in the magnitude of projected aerosol forcing, our results suggest that anthropogenic aerosols, given their geographic distributions and temporal trajectories, strongly influence the high-latitude ocean heat uptake and interhemispheric asymmetry through AMOC change.

Sign in / Sign up

Export Citation Format

Share Document