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Andrey Andreev Makio Honda Yuichiro Kumamoto Masashi Kusakabe Akihiko Murata 《Journal of Oceanography》2001,57(2):177-188
Excess CO2 and pHexcess showing an increase in dissolved inorganic carbon and a decrease in pH from the beginning of the industrial epoch (middle of the 19th century) until the present time have been calculated in the intermediate water layer of the northwestern Pacific and the Okhotsk Sea. It is concluded that: (1) The Kuril Basin (Okhotsk Sea) and the Bussol' Strait areas are characterized by the greatest concentrations of excess CO2 at isopycnal surfaces due to the processes of formation and transformation of intermediate water mass. (2) The largest difference in excess CO2 concentration between the Okhotsk Sea and the western subarctic Pacific (about 8 µmol/kg) is found at the = 27.0. (3) The difference in excess CO2 between the western subarctic Pacific and subtropical regions is significant only in the upper part of the intermediate water layer ( = 26.7–27.0). (4) About 10% of the excess CO2 accumulation in the subtropical north Pacific is determined by water exchange with the subarctic Pacific and the Okhotsk Sea. 相似文献
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Yoshihisa?MinoEmail author Chiho?Sukigara Makio?C.?Honda Hajime?Kawakami Kazuhiko?Matsumoto Masahide?Wakita Minoru?Kitamura Tetsuichi?Fujiki Kosei?Sasaoka Osamu?Abe Jan?Kaiser Toshiro?Saino 《Journal of Oceanography》2016,72(6):819-836
Intensive observations using hydrographical cruises and moored sediment trap deployments during 2010 and 2012 at station K2 in the North Pacific Western Subarctic Gyre (WSG) revealed seasonal changes in δ 15N of both suspended and settling particles. Suspended particles (SUS) were collected from depths between the surface and 200 m; settling particles by drifting sediment traps (DST; 100–200 m) and moored sediment traps (MST; 200 and 500 m). All particles showed higher δ 15N values in winter and lower in summer, contrary to the expected by isotopic fractionation during phytoplankton nitrate consumption. We suggest that these observed isotopic patterns are due to ammonium consumption via light-controlled nitrification, which could induce variations in δ 15N(SUS) of 0.4–3.1 ‰ in the euphotic zone (EZ). The δ 15N(SUS) signature was reflected by δ 15N(DST) despite modifications during biogenic transformation from suspended particles in the EZ. δ 15N enrichment (average: 3.6 ‰) and the increase in C:N ratio (by 1.6) in settling particles suggests year-round contributions of metabolites from herbivorous zooplankton as well as TEPs produced by diatoms. Accordingly, seasonal δ 15N(DST) variations of 2.4–7.0 ‰ showed a significant correlation with primary productivity (PP) at K2. By applying the observed δ 15N(DST) vs. PP regression to δ 15N(MST) of 1.9–8.0 ‰, we constructed the first annual time-series of PP changes in the WSG. This new approach to estimate productivity can be a powerful tool for further understanding of the biological pump in the WSG, even though its validity needs to be examined carefully. 相似文献
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Minoru Kitamura Toru Kobari Makio C. Honda Kazuhiko Matsumoto Kosei Sasaoka Rie Nakamura Kazuyuki Tanabe 《Journal of Oceanography》2016,72(3):387-402
Seasonal changes in mesozooplankton biomass and their community structures were observed at time-series stations K2 (subarctic) and S1 (subtropical) in the western North Pacific Ocean. At K2, the maximum biomass was observed during the spring when primary productivity was still low. The annual mean biomasses in the euphotic and 200- to 1000-m layers were 1.39 (day) and 2.49 (night) g C m?2 and 4.00 (day) and 3.63 (night) g C m?2, respectively. Mesozooplankton vertical distribution was bimodal and mesopelagic peak was observed in a 200- to 300-m layer; it mainly comprised dormant copepods. Copepods predominated in most sampling layers, but euphausiids were dominant at the surface during the night. At S1, the maximum biomass was observed during the spring and the peak timing of biomass followed those of chlorophyll a and primary productivity. The annual mean biomasses in the euphotic and 200- to 1000-m layers were 0.10 (day) and 0.21 (night) g C m?2 and 0.47 (day) and 0.26 (night) g C m?2, respectively. Copepods were dominant in most sampling layers, but their mean proportion was lower than that in K2. Mesozooplankton community characteristics at both sites were compared with those at other time-series stations in the North Pacific and with each other. The annual mean primary productivities and sinking POC fluxes were equivalent at both sites; however, mesozooplankton biomasses were higher at K2 than at S1. The difference of biomasses was probably caused by differences of individual carbon losses, population turnover rates, and trophic structures of communities between the two sites. 相似文献
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Concentrations of nutrients (NO3, NO2, Si(OH)4, PO4 and dissolved inorganic carbon (DIC) were measured in a series of seawater samples collected over approximately 15 months
in 2005 and 2006 by an automatic water sampler (Remote Access Sampler, RAS) in the Northwestern North Pacific. Seasonal variability
and concentrations of NO3 + NO2 (NOx and Si(OH)4 were comparable to previous shipboard observations, although there were small errors associated with measurements of PO4 and DIC. Concentrations of these nutrients began to decrease in late April. After the end of June, NOx and Si(OH)4 decreased rapidly, with large fluctuations. After October, these nutrients increased again until late spring 2006. The ratio
of the decrease of Si(OH)4 to that of NOx suggests that numbers of biogenic opal-producing creatures, such as diatoms, increased after the end of June. This conclusion
was supported by a rapid increase in biogenic opal flux recorded in a sediment trap at 150 m. The relationship between NOx concentrations at the RAS depth of 35 m and NOx integrated over the upper 100 m was determined using previous shipboard hydrocast data. This relationship was used to estimate
integrated mixed layer NOx concentration from RAS data. Estimated new production based on seasonal drawdown of integrated NOx averaged approximately 156 mg-C m−2day−1 annually, which agrees with previous estimates. Thus, an automatic seawater sampler that documents annual maximum and minimum
nutrient concentrations and episodic events such as storms and spring blooms, which might be missed by an ordinary research
vessel, will contribute to time-series observations of nutrients and, by extension, biological pump activity. 相似文献
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Hajime Kawakami Makio C. Honda Masahide Wakita Shuichi Watanabe 《Journal of Oceanography》2007,63(6):967-982
Time-series measurements of dissolved inorganic carbon (DIC) and nutrient concentrations were conducted in the northwestern
North Pacific from October 2002 to August 2004. Assuming that data obtained in different years represented time-series seasonal
data for a single year, vertical distributions of DIC and nutrients showed large seasonal variabilities in the surface layer
(∼100 m). Seasonal variabilities in normalized DIC (nDIC) and nitrate concentrations at the sea surface were estimated to
be 81–113 μmol kg−1 and 12.7–15.7 μmol kg−1, respectively, in the Western Subarctic Gyre. The variability in nutrients between May and July was generally at least double
that in other seasons. In the Western Subarctic Gyre, estimations based on statistical analyses revealed that seasonal new
production was 39–61 gC m−2 and tended to be higher in the southwestern regions or coastal regions. The seasonal new productions in the northwestern
North Pacific were two or more times higher than in the North Pacific subtropical gyre and the northeastern North Pacific.
It is likely that this difference is due to spatial variations in the concentrations of trace metals and the species of phytoplankton
present. In addition, from estimations of surface pCO2 it was verified that the Western Subarctic Gyre is a source of atmospheric CO2 between February and May and a sink for CO2 between July and October. 相似文献
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Masahito Shigemitsu Yutaka W. Watanabe Yasuhiro Yamanaka Hajime Kawakami Makio C. Honda 《Journal of Oceanography》2010,66(5):697-708
We used time-series sediment trap data for four major components, organic matter and ballast minerals (CaCO3, opal, and lithogenic matter) from 150, 540, and 1000 m in the western subarctic Pacific (WSAP), where opal is the predominant
mineral in sinking particles, to develop four simple models for settling particles, including the “ballast model”. The ballast
model is based on the concept that most of the organic matter “rain” in the deep sea is carried by the minerals. These four
models are designed to simultaneously reproduce the flux of each major component of settling particles at 540 and 1000 m by
using the data for each component at 150 m as initial values. Among the four models, the ballast model, which considers the
sinking velocity increase with depth, was identified as the best using the Akaike information criterion as a measure of the
model fit to data. This model successfully reproduced the flux of organic matter at 540 and 1000 m, indicating that the ballast
model concept works well in the shallow zone of the WSAP on a seasonal timescale. This also suggests that ballast minerals
not only physically protect the organic matter from degradation during the settling process but also enhance the sinking velocity
and reduce the degree of decomposition. 相似文献
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The atmosphere-ocean exchange of climatically important gases is determined by the transfer velocity (k) and concentration gradient across the interface. Based on observations in the northwestern subarctic Pacific and Sagami
Bay, we report here the results of the first ever application of the natural abundance of triple isotopes of dissolved oxygen
(16O, 17O and 18O) for direct estimation of k and propose a new relationship with wind speed. The k values estimated from nighttime variations in oxygen isotopes are found to be higher than the direct estimations at low wind
speed (<5 m s−1) and lower at high wind speeds (>13 m s−1) and showed significant spatial variability. The method presented here can be used to derive seasonal and spatial variations
in k and the influence of surface conditions on the value, leading to improved estimates of biogenic/anthropogenic gas exchange
at the air-sea interface. 相似文献