scholarly journals Variations in intermediate and deep ocean circulation in the subtropical northwestern Pacific from 26 ka to present based on a new calibration for Mg/Ca in benthic foraminifera

2014 ◽  
Vol 10 (2) ◽  
pp. 1265-1303 ◽  
Author(s):  
Y. Kubota ◽  
K. Kimoto ◽  
T. Itaki ◽  
Y. Yokoyama ◽  
Y. Miyairi ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Benthic Foraminifera ◽  
North Pacific ◽  
Bottom Water ◽  
Deep Ocean ◽  
Northwestern Pacific ◽  
Okinawa Island ◽  
The North ◽  
Deep Ocean Circulation ◽  
The North Pacific

Abstract. To understand variations in intermediate and deep ocean circulation in the North Pacific, bottom water temperatures (BWT), carbon isotopes (δ13C) of benthic foraminifera, and oxygen isotopes (δ18O) of seawater at a water depth of 1166 m were reconstructed from 26 ka to present. A new regional Mg/Ca calibration for the benthic foraminifera Cibicidoides wuellerstorfi was established to convert the benthic Mg/Ca value to BWT, based on twenty-six surface sediment samples and a core top sample retrieved around Okinawa Island. In addition, core GH08-2004, retrieved from 1166 m water depth east of Okinawa Island, was used to reconstruct water properties from 26 ka to present. During the Last Glacial Maximum (LGM), from 24 to 18 ka, BWT appeared to be relatively constant at approximately 2 °C, which is ~1.5–2 °C lower than today. One of the prominent features of our BWT records was a millennial-scale variation in BWT during the last deglaciation, with BWT higher during Heinrich event 1 (H1; ~17 ka) and the Younger Dryas (YD; ~12 ka) and lower during the Bølling/Allerød (B/A; ~14 ka). The record of seawater δ18O in core GH08-2004 exhibited a rapid increase in association with the rapid warming of BWT at 17 ka, likely due to the reduced precipitation in the North Pacific in response to less moisture transport from the equatorial Atlantic as a result of the collapse of the Atlantic Meridional Overturning Circulation. During the interval from 17 to 15 ka, the bottom water temperature tended to decrease in association with a decrease in the carbon isotope values of C. wuellerstorfi, likely as a result of increased upwelling of the older water mass that was stored in the abyssal Pacific during the glacial time. The timing of the increased upwelling coincided with the deglacial atmospheric CO2 rise initiated at ~17 ka, and suggested that the increased upwelling in the subtropical northwestern Pacific from 17 to 15 ka contributed to the carbon release from the Pacific into the atmosphere.

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.

Geographical restriction as a guide to the causes of extinction: the case of the cold northern oceans during the Neogene

Paleobiology ◽  
1989 ◽  
Vol 15 (4) ◽  
pp. 335-356 ◽  
Author(s):  
Geerat J. Vermeij
Keyword(s):  
Primary Productivity ◽  
North Pacific ◽  
Early Pleistocene ◽  
Northwestern Pacific ◽  
Supporting Evidence ◽  
Geographical Patterns ◽  
The North ◽  
The Pacific ◽  
Late Neogene ◽  
The North Pacific

Geographical restriction to refuges implies the regional extinction of taxa in areas of the previous range falling outside the refuge. A comparison of the circumstances in the refuge with those in areas from which the taxa were eliminated is potentially informative for pinpointing the causes of extinction. A synthesis of data on the geographical and stratigraphical distributions of cool-water molluscs of the North Pacific and North Atlantic Oceans during the late Neogene reveals four patterns of geographical restriction, at least two of which imply that climatic cooling was not the only cause of extinction during the last several million years. These four patterns are (1) the northwestern Pacific restriction, involving 15 taxa whose amphi-Pacific distributions during the late Neogene became subsequently restricted to the Asian side of the Pacific; (2) the northwestern Atlantic restriction, involving six taxa whose early Pleistocene distribution is inferred to have been amphi-Atlantic, but whose present-day and late Pleistocene ranges are confined to the northwestern Atlantic; (3) a vicariant Pacific pattern, in which many ancestral amphi-Pacific taxa gave rise to separate eastern and western descendants; and (4) the circumboreal restriction, involving six taxa whose early Pleistocene distribution, encompassing both the Atlantic and Pacific Oceans, became subsequently limited to the North Pacific. Like the Pliocene extinctions in the Atlantic, previously studied by Stanley and others, the vicariant Pacific pattern is most reasonably interpreted as having resulted from regional extinction of northern populations in response to cooling. The northwestern Pacific and Atlantic restrictions, however, cannot be accounted for in this way. In contrast to the northeastern margins of the Pacific and Atlantic, the northwestern margins are today characterized by wide temperature fluctuations and by extensive development of shore ice in winter. Northeastern, rather than northwestern, restriction would be expected if cooling were the overriding cause of regional extinction. Among the other possible causes of extinction, only a decrease in primary productivity can account for the observed northwestern and circumboreal patterns of restriction. Geographical patterns of body size and the distribution of siliceous deposits provide supporting evidence that primary productivity declined after the Miocene in the northeastern Pacific, but remained high in the northwestern Pacific, and that productivity in the Pacific is generally higher than it is in the Atlantic. The patterns of geographical restriction in the northern oceans thus provide additional support to previous inferences that reductions in primary productivity have played a significant role in marine extinctions.

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.

Bottom water warming in the North Pacific Ocean

Nature ◽  
2004 ◽  
Vol 427 (6977) ◽  
pp. 825-827 ◽  
Author(s):  
Masao Fukasawa ◽  
Howard Freeland ◽  
Ron Perkin ◽  
Tomowo Watanabe ◽  
Hiroshi Uchida ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
Bottom Water ◽  
North Pacific Ocean ◽  
The North ◽  
The North Pacific

Removing the North Pacific halocline: Effects on global climate, ocean circulation and the carbon cycle

2012 ◽  
Vol 61-64 ◽  
pp. 106-113 ◽  
Author(s):  
L. Menviel ◽  
A. Timmermann ◽  
O. Elison Timm ◽  
A. Mouchet ◽  
A. Abe-Ouchi ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Ocean Circulation ◽  
North Pacific ◽  
Global Climate ◽  
The North ◽  
The North Pacific

scholarly journals Winter Extreme Flux Events in the Kuroshio and Gulf Stream Extension Regions and Relationship with Modes of North Pacific and Atlantic Variability

2015 ◽  
Vol 28 (12) ◽  
pp. 4950-4970 ◽  
Author(s):  
Xiaohui Ma ◽  
Ping Chang ◽  
R. Saravanan ◽  
Dexing Wu ◽  
Xiaopei Lin ◽  
...  
Keyword(s):  
North Pacific ◽  
Gulf Stream ◽  
Kuroshio Extension ◽  
Storm Track ◽  
Propagation Path ◽  
Northwestern Pacific ◽  
Boreal Winter ◽  
The North ◽  
The Kuroshio ◽  
The North Pacific

Abstract Boreal winter (November–March) extreme flux events in the Kuroshio Extension region (KER) of the northwestern Pacific and the Gulf Stream region (GSR) of the northwestern Atlantic are analyzed and compared, based on NCEP Climate Forecast System Reanalysis (CFSR), NCEP–NCAR reanalysis, and NOAA Twentieth Century Reanalysis data, as well as the observationally derived OAFlux dataset. These extreme flux events, most of which last less than 3 days, are characterized by cold air outbreaks (CAOs) with an anomalous northerly wind that brings cold and dry air from the Eurasian and North American continents to the KER and GSR, respectively. A close relationship between the extreme flux events over KER (GSR) and the Aleutian low pattern (ALP) [east Atlantic pattern (EAP)] is found with more frequent occurrence of the extreme flux events during a positive ALP (EAP) phase and vice versa. A further lag-composite analysis suggests that the ALP (EAP) is associated with accumulated effects of the synoptic winter storms accompanied by the extreme flux events and shows that the event-day storms tend to have a preferred southeastward propagation path over the North Pacific (Atlantic), potentially contributing to the southward shift of the storm track over the eastern North Pacific (Atlantic) basin during the ALP (EAP) positive phase. Finally, lag-regression analyses indicate a potential positive influence of sea surface temperature (SST) anomalies along the KER (GSR) on the development of the extreme flux events in the North Pacific (Atlantic).

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