Impact of Explosive Cyclones on the Deep Ocean in the North Pacific: Simulations and Observations

2018 ◽  
Author(s):  
Akira Kuwano-Yoshida ◽  
Hideharu Sasaki ◽  
Yoshikazu Sasai ◽  
Shigeki Hosoda
Keyword(s):  
North Pacific ◽  
Deep Ocean ◽  
The North ◽  
Explosive Cyclones ◽  
The North Pacific

scholarly journals Millennial-scale variations in sedimentary oxygenation in the western subtropical North Pacific and its links to North Atlantic climate

2020 ◽  
Vol 16 (1) ◽  
pp. 387-407 ◽  
Author(s):  
Jianjun Zou ◽  
Xuefa Shi ◽  
Aimei Zhu ◽  
Selvaraj Kandasamy ◽  
Xun Gong ◽  
...  
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Deep Ocean ◽  
Co2 Concentration ◽  
Atmospheric Co2 ◽  
Intermediate Water ◽  
The North ◽  
Geochemical Parameters ◽  
The North Pacific ◽  
Millennial Scale

Abstract. The deep-ocean carbon cycle, especially carbon sequestration and outgassing, is one of the mechanisms to explain variations in atmospheric CO2 concentrations on millennial and orbital timescales. However, the potential role of subtropical North Pacific subsurface waters in modulating atmospheric CO2 levels on millennial timescales is poorly constrained. An increase in the respired CO2 concentration in the glacial deep-ocean due to biological pump generally corresponds to deoxygenation in the ocean interior. This link thus offers a chance to study oceanic ventilation and coeval export productivity based on redox-controlled sedimentary geochemical parameters. Here, we investigate a suite of geochemical proxies in a sediment core from the Okinawa Trough to understand sedimentary oxygenation variations in the subtropical North Pacific over the last 50 000 years (50 ka). Our results suggest that enhanced mid-depth western subtropical North Pacific (WSTNP) sedimentary oxygenation occurred during cold intervals and after 8.5 ka, while oxygenation decreased during the Bölling-Alleröd (B/A) and Preboreal. The enhanced oxygenation during cold spells is linked to the North Pacific Intermediate Water (NPIW), while interglacial increase after 8.5 ka is linked to an intensification of the Kuroshio Current due to strengthened northeast trade winds over the tropics. The enhanced formation of the NPIW during Heinrich Stadial 1 (HS1) was likely driven by the perturbation of sea ice formation and sea surface salinity oscillations in the high-latitude North Pacific. The diminished sedimentary oxygenation during the B/A due to a decreased NPIW formation and enhanced export production, indicates an expansion of the oxygen minimum zone in the North Pacific and enhanced CO2 sequestration at mid-depth waters, along with the termination of atmospheric CO2 concentration increase. We attribute the millennial-scale changes to an intensified NPIW and enhanced abyss flushing during deglacial cold and warm intervals, respectively, closely related to variations in North Atlantic Deep Water formation.

scholarly journals Phosphate availability and the ultimate control of new nitrogen input by nitrogen fixation in the tropical Pacific Ocean

2008 ◽  
Vol 5 (1) ◽  
pp. 95-109 ◽  
Author(s):  
T. Moutin ◽  
D. M. Karl ◽  
S. Duhamel ◽  
P. Rimmelin ◽  
P. Raimbault ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Pacific Ocean ◽  
N2 Fixation ◽  
North Pacific ◽  
North Pacific Ocean ◽  
Deep Ocean ◽  
Phosphate Limitation ◽  
Iron Availability ◽  
The North ◽  
The North Pacific

Abstract. Due to the low atmospheric input of phosphate into the open ocean, it is one of the key nutrients that could ultimately control primary production and carbon export into the deep ocean. The observed trend over the last 20 years has shown a decrease in the dissolved inorganic phosphate (DIP) pool in the North Pacific gyre, which has been correlated to the increase in di-nitrogen (N2) fixation rates. Following a NW-SE transect, in the Southeast Pacific during the early austral summer (BIOSOPE cruise), we present data on DIP, dissolved organic phosphate (DOP) and particulate phosphate (PP) pools along with DIP turnover times (TDIP) and N2 fixation rates. We observed a decrease in DIP concentration from the edges to the centre of the gyre. Nevertheless the DIP concentrations remained above 100 nmol L−1 and T DIP was more than 6 months in the centre of the gyre; DIP availability remained largely above the level required for phosphate limitation to occur and the absence of Trichodesmium spp and low nitrogen fixation rates were likely to be controlled by other factors such as temperature or iron availability. This contrasts with recent observations in the North Pacific Ocean at the ALOHA station and in the western Pacific Ocean at the same latitude (DIAPALIS cruises) where lower DIP concentrations (<20 nmol L−1) and T DIP <50 h were measured during the summer season in the upper layer. The South Pacific gyre can be considered a High Phosphate Low Chlorophyll (HPLC) oligotrophic area, which could potentially support high N2 fixation rates and possibly carbon dioxide sequestration, if the primary ecophysiological controls, temperature and/or iron availability, were alleviated.

Pacific Meridional Overturning Circulation during the Mid-Pliocene Warm Period

2020 ◽  
Author(s):  
Heather L. Ford ◽  
Natalie Burls ◽  
David Hodell
Keyword(s):  
North Pacific ◽  
Deep Ocean ◽  
Warm Period ◽  
Meridional Overturning Circulation ◽  
Future Climate Change ◽  
Intermediate Water ◽  
Overturning Circulation ◽  
The North ◽  
Meridional Overturning ◽  
The North Pacific

&lt;p&gt;Today in the North Pacific only intermediate water forms because of a strong halocline, but Pacific Meridional Overturning Circulation (PMOC) may have existed in the past. The mid-Pliocene warm period (3.264-3.025 Ma) is a time of sustained warmth where atmospheric carbon dioxide concentrations were similar to today and the northern hemisphere was relatively ice free &amp;#8211; making it a pseudo-analogue for future climate change. North Pacific sedimentological and climate modeling evidence suggests a PMOC formed during this time. &amp;#160;To determine the spatial extent of a PMOC during the mid-Pliocene warm period, we constructed a depth transect of sites between 2400 to 3400 m water depth on Shatsky Rise by measuring stable isotopes of &lt;em&gt;Cibicidoides wuellerstorfi&lt;/em&gt;. We compare these new results with previously published records and calculate anomalies using the OC3 water column and core-top data products. The &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C spatial pattern is consistent with a modest PMOC of intermediate depth (core ~2000 m) extending to the equator during the mid-Pliocene warm period. Ventilation of the North Pacific by a PMOC has broad implications for deep ocean carbon storage as the North Pacific contains the oldest, carbon-rich waters today. Future work will include minor and trace element analyses to determine the temperature and carbon characteristics of the PMOC water mass and comparisons with PlioMIP modeling outputs.&lt;/p&gt;

scholarly journals A simple mixing explanation for late Pleistocene changes in the Pacific-South Atlantic benthic δ<sup>13</sup>C gradient

2009 ◽  
Vol 5 (6) ◽  
pp. 2607-2630 ◽  
Author(s):  
L. E. Lisiecki
Keyword(s):  
Late Pleistocene ◽  
Deep Water ◽  
North Pacific ◽  
Deep Ocean ◽  
South Atlantic ◽  
The North ◽  
The Pacific ◽  
The Last Glacial Maximum ◽  
The North Pacific ◽  
The Last Glacial

Abstract. The fact that the deep-ocean benthic δ13C minimum shifted from the North Pacific to the South Atlantic during the Last Glacial Maximum is often interpretted as evidence of a change in deep water circulation, such as the development of deep water ventilation in the North Pacific. This study re-evaluates the implications of changes in benthic δ13C gradients by comparing Pacific Deep Water (PDW) δ13C measurements with the values expected for the null hypothesis that PDW ventilation sources remained unchanged throughout the Late Pleistocene. The δ13C compositions of PDW, Northern Component Water (NCW) and Southern Component Water (SCW) are estimated from regional benthic δ13C stacks of 3–6 sites. Changes in PDW δ13C and PDW-SCW δ13C gradients over the past 800 kyr are found to be well described by a constant mixture of 60% NCW and 40% SCW plus a constant Pacific "age" offset of −0.5‰. Thus, an additional ventilation source for glacial PDW (e.g., in the North Pacific) cannot be inferred solely on the basis of changes in the Pacific-South Atlantic benthic δ13C gradient.

scholarly journals A simple mixing explanation for late Pleistocene changes in the Pacific-South Atlantic benthic δ<sup>13</sup>C gradient

2010 ◽  
Vol 6 (3) ◽  
pp. 305-314 ◽  
Author(s):  
L. E. Lisiecki
Keyword(s):  
Late Pleistocene ◽  
Deep Water ◽  
North Pacific ◽  
Deep Ocean ◽  
South Atlantic ◽  
The North ◽  
The Pacific ◽  
The Last Glacial Maximum ◽  
The North Pacific ◽  
The Last Glacial

Abstract. The fact that the deep-ocean benthic δ13C minimum shifted from the North Pacific to the South Atlantic during the Last Glacial Maximum is often interpretted as evidence of a change in deep water circulation, such as the development of deep water ventilation in the North Pacific or a decrease in Southern Ocean overturning. This study re-evaluates the implications of changes in benthic δ13C gradients by comparing Pacific Deep Water (PDW) δ13C measurements with the values expected for the null hypothesis that PDW ventilation sources remained unchanged throughout the Late Pleistocene. The δ13C compositions of PDW, Northern Component Water (NCW) and Southern Component Water (SCW) are estimated from regional benthic δ13C stacks of 3–6 sites. Changes in PDW δ13C and PDW-SCW δ13C gradients over the past 800 kyr are found to be well described by a constant mixture of 60% NCW and 40% SCW plus a constant Pacific remineralization offset of −0.5‰. Thus, a change in PDW ventilation cannot be inferred solely on the basis of changes in the Pacific-South Atlantic benthic δ13C gradient.

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.

Observations of wind-forced deep ocean currents in the North Pacific

1989 ◽  
Vol 94 (C8) ◽  
pp. 10773 ◽  
Author(s):  
C. J. Koblinsky ◽  
P. P. Niiler ◽  
W. J. Schmitz
Keyword(s):  
North Pacific ◽  
Deep Ocean ◽  
Ocean Currents ◽  
The North ◽  
Deep Ocean Currents ◽  
The North Pacific
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