scholarly journals The global ocean circulation on a retrograde rotating earth

2011 ◽  
Vol 7 (2) ◽  
pp. 487-499 ◽  
Author(s):  
V. Kamphuis ◽  
S. E. Huisman ◽  
H. A. Dijkstra
Keyword(s):  
Ocean Circulation ◽  
Deep Water ◽  
North Pacific ◽  
Global Ocean ◽  
Freshwater Flux ◽  
Deep Water Formation ◽  
The North ◽  
Water Formation ◽  
Global Ocean Circulation ◽  
The North Pacific

Abstract. To understand the three-dimensional ocean circulation patterns that have occurred in past continental geometries, it is crucial to study the role of the present-day continental geometry and surface (wind stress and buoyancy) forcing on the present-day global ocean circulation. This circulation, often referred to as the Conveyor state, is characterised by an Atlantic Meridional Overturning Circulation (MOC) with a deep water formation at northern latitudes and the absence of such a deep water formation in the North Pacific. This MOC asymmetry is often attributed to the difference in surface freshwater flux: the Atlantic as a whole is a basin with net evaporation, while the Pacific receives net precipitation. This issue is revisited in this paper by considering the global ocean circulation on a retrograde rotating earth, computing an equilibrium state of the coupled atmosphere-ocean-land surface-sea ice model CCSM3. The Atlantic-Pacific asymmetry in surface freshwater flux is indeed reversed, but the ocean circulation pattern is not an Inverse Conveyor state (with deep water formation in the North Pacific) as there is relatively weak but intermittently strong deep water formation in the North Atlantic. Using a fully-implicit, global ocean-only model the stability properties of the Atlantic MOC on a retrograde rotating earth are also investigated, showing a similar regime of multiple equilibria as in the present-day case. These results indicate that the present-day asymmetry in surface freshwater flux is not the most important factor setting the Atlantic-Pacific salinity difference and, thereby, the asymmetry in the global MOC.

scholarly journals The global ocean circulation on a retrograde rotating earth

2010 ◽  
Vol 6 (6) ◽  
pp. 2455-2482
Author(s):  
V. Kamphuis ◽  
S. E. Huisman ◽  
H. A. Dijkstra
Keyword(s):  
Ocean Circulation ◽  
Deep Water ◽  
North Pacific ◽  
Global Ocean ◽  
Freshwater Flux ◽  
Deep Water Formation ◽  
The North ◽  
Water Formation ◽  
Global Ocean Circulation ◽  
The North Pacific

Abstract. To understand the three-dimensional ocean circulation patterns that have occurred in past continental geometries, it is crucial to study the role of the present-day continental geometry and surface (wind stress and buoyancy) forcing on the present-day global ocean circulation. This circulation, often referred to as the Conveyor state, is characterized by an Atlantic Meridional Overturning Circulation (MOC) with deep water formation at northern latitudes and the absence of such deep water formation in the North Pacific. This MOC asymmetry is often attributed to the difference in surface freshwater flux: the North Atlantic is a basin with net evaporation, while the North Pacific receives net precipitation. This issue is revisited in this paper by considering the global ocean circulation on a retrograde rotating earth, computing an equilibrium state of the coupled atmosphere-ocean-land surface-sea ice model CCSM3. The Atlantic-Pacific asymmetry in surface freshwater flux is indeed reversed but the ocean circulation pattern is not an Inverse Conveyor state (with deep water formation in the North Pacific) as there is strong and highly variable deep water formation in the North Atlantic. Using a fully-implicit, global ocean-only model also the stability properties of the Atlantic MOC on a retrograde rotating earth are investigated, showing a similar regime of multiple equilibria as in the present-day case. These results demonstrate that the present-day asymmetry in surface freshwater flux is not a crucial factor for the Atlantic-Pacific asymmetry in the global MOC.

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.

Deep‐Water Formation in the North Pacific During the Late Miocene Global Cooling

2021 ◽  
Vol 36 (2) ◽  
Author(s):  
Lina Zhai ◽  
Shiming Wan ◽  
Christophe Colin ◽  
Debo Zhao ◽  
Yuntao Ye ◽  
...  
Keyword(s):  
Deep Water ◽  
Late Miocene ◽  
North Pacific ◽  
Deep Water Formation ◽  
The North ◽  
Global Cooling ◽  
Water Formation ◽  
The North Pacific

scholarly journals Deep water formation in the North Pacific and deglacial CO2rise

2014 ◽  
Vol 29 (6) ◽  
pp. 645-667 ◽  
Author(s):  
James W. B. Rae ◽  
Michael Sarnthein ◽  
Gavin L. Foster ◽  
Andy Ridgwell ◽  
Pieter M. Grootes ◽  
...  
Keyword(s):  
Deep Water ◽  
North Pacific ◽  
Deep Water Formation ◽  
The North ◽  
Water Formation ◽  
The North Pacific

A dynamic giant: changes in North Pacific circulation, biogeochemistry, and CO2 over the last ice age

2020 ◽  
Author(s):  
James Rae ◽  
William Gray ◽  
Louisa Bradtmiller ◽  
Andrea Burke ◽  
Holger Gebhardt ◽  
...  
Keyword(s):  
Deep Water ◽  
North Pacific ◽  
System Modeling ◽  
Climate System ◽  
Ice Age ◽  
Deep Water Formation ◽  
The North ◽  
Water Formation ◽  
The Impact ◽  
The North Pacific

<p>The North Pacific has been thought of as a sleeping giant in Earth’s climate system.  Despite being a major reservoir of heat, nutrients, and carbon, the lack of deep water formation in this region today limits the exchange of these properties.  Here, using a variety of new and published sediment core data, alongside Earth system modeling, we provide evidence that the North Pacific giant is in fact a dynamic player in Earth’s climate system, with active PMOC during the LGM and deep water formation during HS1.  We also demonstrate a persistent Atlantic-Pacific seesaw in deep water formation during rapid climate change events, and discuss the impact of these changes on regional climate and global CO<sub>2</sub>.</p>

scholarly journals Does Net E − P Set a Preference for North Atlantic Sinking?

2012 ◽  
Vol 42 (11) ◽  
pp. 1781-1792 ◽  
Author(s):  
Selma E. Huisman ◽  
Henk A. Dijkstra ◽  
A. S. von der Heydt ◽  
W. P. M. de Ruijter
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
North Pacific ◽  
Multiple Equilibria ◽  
Meridional Overturning Circulation ◽  
Global Ocean ◽  
Overturning Circulation ◽  
The North ◽  
Meridional Overturning ◽  
The North Pacific

Abstract The present-day global meridional overturning circulation (MOC) with formation of North Atlantic Deep Water (NADW) and the absence of a deep-water formation in the North Pacific is often considered to be caused by the fact that the North Pacific basin is a net precipitative, while the North Atlantic is a net evaporative basin. In this paper, the authors study the effect of asymmetries in continent geometry and freshwater fluxes on the MOC both in an idealized two-dimensional model and in a global ocean model. This study approaches the problem from a multiple equilibria perspective, where asymmetries in external factors constrain the existence of steady MOC patterns. Both this multiple equilibria perspective and the fact that a realistic global geometry is used add new aspects to the problem. In the global model, it is shown that the Atlantic forced by net precipitation can have a meridional overturning circulation with northern sinking and a sea surface salinity that resembles the present-day salinity field. The model results are suggestive of the importance of factors other than the freshwater flux asymmetries, in particular continental asymmetries, in producing the meridional overturning asymmetry.

Constraining sources and relative flow rates of bottom waters in the Late Cretaceous Pacific Ocean

Geology ◽  
2020 ◽  
Vol 48 (5) ◽  
pp. 509-513 ◽  
Author(s):  
Shannon J. Haynes ◽  
Kenneth G. MacLeod ◽  
Jean-Baptiste Ladant ◽  
Andrew Vande Guchte ◽  
Masoud A. Rostami ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Deep Water ◽  
Deep Convection ◽  
Source Region ◽  
Source Area ◽  
Geochemical Data ◽  
Deep Water Formation ◽  
The North ◽  
Water Formation ◽  
Bottom Waters

Abstract Geochemical data suggest that ocean circulation patterns changed over a period of long-term cooling during the last 10 m.y. of the Cretaceous (late Campanian–Maastrichtian). Proposed changes include enhanced deep-water formation in the South Atlantic and/or Indian sectors of the Southern Ocean, initiation or enhanced deep-water formation in the North Atlantic, and alternating regions of deep convection in the North and South Pacific. Existing geochemical data do not allow simple confirmation or rejection of any of these scenarios. To test Pacific circulation during the Maastrichtian, we measured neodymium isotopic (εNd) values from four Pacific Deep Sea Drilling Project and Ocean Drilling Program sites and compare results both to Earth system model simulations using Maastrichtian paleogeography and to previous studies. Pacific εNd results consistently show a small negative εNd excursion during a well-documented, ∼1–3 m.y. early Maastrichtian cooling pulse (EMCP) but no other consistent trends across the late Campanian–late Maastrichtian interval (∼10 m.y.). Model results show that different CO2 forcings lead to changes in rates, but not patterns, of circulation. These combined results support the existence of a sustained source region for intermediate and deep waters in the southwestern Pacific throughout the late Campanian–Maastrichtian and indicate that changes in εNd values during the EMCP reflect an increased rate of overturning in the Pacific rather than changes in the source area of Pacific bottom waters.

scholarly journals Radioisotope constraints of Arctic deep water export to the North Atlantic

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Lauren E. Kipp ◽  
Jerry F. McManus ◽  
Markus Kienast
Keyword(s):  
Ocean Circulation ◽  
North Atlantic ◽  
Deep Water ◽  
Particle Flux ◽  
The Arctic ◽  
Global Ocean ◽  
Central Basin ◽  
The North ◽  
Crucial Component ◽  
Global Ocean Circulation

AbstractThe export of deep water from the Arctic to the Atlantic contributes to the formation of North Atlantic Deep Water, a crucial component of global ocean circulation. Records of protactinium-231 (231Pa) and thorium-230 (230Th) in Arctic sediments can provide a measure of this export, but well-constrained sedimentary budgets of these isotopes have been difficult to achieve in the Arctic Ocean. Previous studies revealed a deficit of 231Pa in central Arctic sediments, implying that some 231Pa is either transported to the margins, where it may be removed in areas of higher particle flux, or exported from the Arctic via deep water advection. Here we investigate this “missing sink” of Arctic 231Pa and find moderately increased 231Pa deposition along Arctic margins. Nonetheless, we determine that most 231Pa missing from the central basin must be lost via advection into the Nordic Seas, requiring deep water advection of 1.1 – 6.4 Sv through Fram Strait.

Effects of Mountains and Ice Sheets on Global Ocean Circulation*

2011 ◽  
Vol 24 (11) ◽  
pp. 2814-2829 ◽  
Author(s):  
Andreas Schmittner ◽  
Tiago A. M. Silva ◽  
Klaus Fraedrich ◽  
Edilbert Kirk ◽  
Frank Lunkeit
Keyword(s):  
Ocean Circulation ◽  
Deep Water ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Meridional Overturning Circulation ◽  
Global Ocean ◽  
Deep Water Formation ◽  
The Pacific ◽  
Water Formation ◽  
Meridional Overturning

Abstract The impact of mountains and ice sheets on the large-scale circulation of the world’s oceans is investigated in a series of simulations with a new coupled ocean–atmosphere model [Oregon State University–University of Victoria model (OSUVic)], in which the height of orography is scaled from 1.5 times the actual height (at T42 resolution) to 0 (no mountains). The results suggest that the effects of mountains and ice sheets on the buoyancy and momentum transfer from the atmosphere to the surface ocean determine the present pattern of deep ocean circulation. Higher mountains reduce water vapor transport from the Pacific and Indian Oceans into the Atlantic Ocean and contribute to increased (decreased) salinities and enhanced (reduced) deep-water formation and meridional overturning circulation in the Atlantic (Pacific). Orographic effects also lead to the observed interhemispheric asymmetry of midlatitude zonal wind stress. The presence of the Antarctic ice sheet cools winter air temperatures by more than 20°C directly above the ice sheet and sets up a polar meridional overturning cell in the atmosphere. The resulting increased meridional temperature gradient strengthens midlatitude westerlies by ~25% and shifts them poleward by ~10°. This leads to enhanced and poleward-shifted upwelling of deep waters in the Southern Ocean, a stronger Antarctic Circumpolar Current, increased poleward atmospheric moisture transport, and more advection of high-salinity Indian Ocean water into the South Atlantic. Thus, it is the current configuration of mountains and ice sheets on earth that determines the difference in deep-water formation between the Atlantic and the Pacific.

scholarly journals Freshening of the Labrador Sea as a trigger for Little Ice Age development

2017 ◽  
Vol 13 (4) ◽  
pp. 317-331 ◽  
Author(s):  
Montserrat Alonso-Garcia ◽  
Helga (Kikki) F. Kleiven ◽  
Jerry F. McManus ◽  
Paola Moffa-Sanchez ◽  
Wallace S. Broecker ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
North Atlantic ◽  
Deep Water ◽  
Little Ice Age ◽  
Ice Age ◽  
Labrador Sea ◽  
Deep Water Formation ◽  
The North ◽  
Water Formation ◽  
The North Atlantic

Abstract. Arctic freshwater discharges to the Labrador Sea from melting glaciers and sea ice can have a large impact on ocean circulation dynamics in the North Atlantic, modifying climate and deep water formation in this region. In this study, we present for the first time a high resolution record of ice rafting in the Labrador Sea over the last millennium to assess the effects of freshwater discharges in this region on ocean circulation and climate. The occurrence of ice-rafted debris (IRD) in the Labrador Sea was studied using sediments from Site GS06-144-03 (57.29° N, 48.37° W; 3432 m water depth). IRD from the fraction 63–150 µm shows particularly high concentrations during the intervals  ∼  AD 1000–1100,  ∼  1150–1250,  ∼  1400–1450,  ∼  1650–1700 and  ∼  1750–1800. The first two intervals occurred during the Medieval Climate Anomaly (MCA), whereas the others took place within the Little Ice Age (LIA). Mineralogical identification indicates that the main IRD source during the MCA was SE Greenland. In contrast, the concentration and relative abundance of hematite-stained grains reflects an increase in the contribution of Arctic ice during the LIA. The comparison of our Labrador Sea IRD records with other climate proxies from the subpolar North Atlantic allowed us to propose a sequence of processes that led to the cooling that occurred during the LIA, particularly in the Northern Hemisphere. This study reveals that the warm climate of the MCA may have enhanced iceberg calving along the SE Greenland coast and, as a result, freshened the subpolar gyre (SPG). Consequently, SPG circulation switched to a weaker mode and reduced convection in the Labrador Sea, decreasing its contribution to the North Atlantic deep water formation and, thus, reducing the amount of heat transported to high latitudes. This situation of weak SPG circulation may have made the North Atlantic climate more unstable, inducing a state in which external forcings (e.g. reduced solar irradiance and volcanic eruptions) could easily drive periods of severe cold conditions in Europe and the North Atlantic like the LIA. This analysis indicates that a freshening of the SPG may play a crucial role in the development of cold events during the Holocene, which may be of key importance for predictions about future climate.

Sign in / Sign up

Export Citation Format

Share Document