scholarly journals Episodic subduction patches in the western North Pacific identified from BGC-Argo float data

2021 ◽  
Vol 18 (19) ◽  
pp. 5539-5554
Author(s):  
Shuangling Chen ◽  
Mark L. Wells ◽  
Rui Xin Huang ◽  
Huijie Xue ◽  
Jingyuan Xi ◽  
...  
Keyword(s):  
North Pacific ◽  
Western North Pacific ◽  
Global Climate ◽  
Kuroshio Extension ◽  
Small Scale ◽  
Thermocline Depth ◽  
Episodic Events ◽  
Biogeochemical Models ◽  
Mesopelagic Zone ◽  
Mixed Layers

Abstract. Subduction associated with mesoscale eddies is an important but difficult-to-observe process that can efficiently export carbon and oxygen to the mesopelagic zone (100–1000 dbar). Using a novel BGC-Argo dataset covering the western North Pacific (20–50∘ N, 120–180∘ E), we identified imprints of episodic subduction using anomalies in dissolved oxygen and spicity, a water mass marker. These subduction patches were present in 4.0 % (288) of the total profiles (7120) between 2008 and 2019, situated mainly in the Kuroshio Extension region between March and August (70.6 %). Roughly 31 % and 42 % of the subduction patches were identified below the annual permanent pycnocline depth (300 m vs. 450 m) in the subpolar and subtropical regions, respectively. Around half (52 %) of these episodic events injected oxygen-enriched waters below the maximum annual permanent thermocline depth (450 dbar), with >20 % occurring deeper than 600 dbar. Subduction patches were detected during winter and spring when mixed layers are deep. The oxygen inventory within these subductions is estimated to be on the order of 64 to 152 g O2/m2. These mesoscale events would markedly increase oxygen ventilation as well as carbon removal in the region, both processes helping to support the nutritional and metabolic demands of mesopelagic organisms. Climate-driven patterns of increasing eddy kinetic energies in this region imply that the magnitude of these processes will grow in the future, meaning that these unexpectedly effective small-scale subduction processes need to be better constrained in global climate and biogeochemical models.

scholarly journals Episodic subduction patches in the western North Pacific identified from BGC-Argo float Data

2021 ◽  
Author(s):  
Shuangling Chen ◽  
Mark L. Wells ◽  
Rui Xin Huang ◽  
Huijie Xue ◽  
Jingyuan Xi ◽  
...  
Keyword(s):  
North Pacific ◽  
Western North Pacific ◽  
Global Climate ◽  
Kuroshio Extension ◽  
Small Scale ◽  
Thermocline Depth ◽  
Episodic Events ◽  
Biogeochemical Models ◽  
Mesopelagic Zone ◽  
The Kuroshio

Abstract. Subduction associated with mesoscale eddies is an important but difficult to observe process that can efficiently export carbon and oxygen to the mesopelagic zone (100–1000 db). Using a novel BGC-Argo dataset covering the western North Pacific (20–50° N, 120–180° E), we identified imprints of episodic subduction using anomalies in dissolved oxygen and spicity, a water mass marker. These subduction patches were present in 4.0 % (288) of the total profiles (7,120) between 2008 and 2019, situated mainly in the Kuroshio Extension region between March and August (70.6 %). Unlike eddy subduction processes observed at higher latitudes, roughly half (52 %) of these episodic events injected carbon- and oxygen-enriched waters below the annual permanent thermocline depth (450 db), with > 20 % occurring deeper than 600 db. Export rates within these subductions are estimated to be on the order of 85–159 mg C m−2 day−1 and 175 to 417 mg O2 m−2 day−1. These mesoscale events would markedly increase carbon removal above that due to biological gravitational settling as well as oxygen ventilation in the region, both helping to support the nutritional and metabolic demands of mesopelagic organisms. Climate-driven patterns of increasing eddy kinetic energies in this region imply that the magnitude of these processes will grow in the future, meaning that these unexpectedly effective small-scale subduction processes need to be better constrained in global climate and biogeochemical models.

scholarly journals Importance of Resolving Kuroshio Front and Eddy Influence in Simulating the North Pacific Storm Track

2017 ◽  
Vol 30 (5) ◽  
pp. 1861-1880 ◽  
Author(s):  
Xiaohui Ma ◽  
Ping Chang ◽  
R. Saravanan ◽  
Raffaele Montuoro ◽  
Hisashi Nakamura ◽  
...  
Keyword(s):  
North Pacific ◽  
Large Scale ◽  
Climate Model ◽  
Kuroshio Extension ◽  
Storm Track ◽  
Small Scale ◽  
Low Resolution ◽  
The North ◽  
The North Pacific ◽  
Sst Anomalies

Abstract Local and remote atmospheric responses to mesoscale SST anomalies associated with the oceanic front and eddies in the Kuroshio Extension region (KER) are studied using high- (27 km) and low-resolution (162 km) regional climate model simulations in the North Pacific. In the high-resolution simulations, removal of mesoscale SST anomalies in the KER leads to not only a local reduction in cyclogenesis but also a remote large-scale equivalent barotropic response with a southward shift of the downstream storm track and jet stream in the eastern North Pacific. In the low-resolution simulations, no such significant remote response is found when mesoscale SST anomalies are removed. The difference between the high- and low-resolution model simulated atmospheric responses is attributed to the effect of mesoscale SST variability on cyclogenesis through moist baroclinic instability. It is only when the model has sufficient resolution to resolve small-scale diabatic heating that the full effect of mesoscale SST forcing on the storm track can be correctly simulated.

scholarly journals Interannual to Decadal Variability of the Upper-Ocean Heat Content in the Western North Pacific and Its Relationship to Oceanic and Atmospheric Variability

2018 ◽  
Vol 31 (13) ◽  
pp. 5107-5125 ◽  
Author(s):  
Hanna Na ◽  
Kwang-Yul Kim ◽  
Shoshiro Minobe ◽  
Yoshi N. Sasaki
Keyword(s):  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
Decadal Variability ◽  
Kuroshio Extension ◽  
Heat Content ◽  
Western Boundary ◽  
Delayed Response ◽  
Atmospheric Variability ◽  
Wind Stress Curl

Three-dimensional oceanic thermal structures and variability in the western North Pacific (NP) are examined on the interannual to decadal time scales and their relationship to oceanic and atmospheric variability is discussed by analyzing observation and reanalysis data for 45 years (1964–2008), which is much longer than the satellite-altimetry period. It is shown that the meridional shift of the Kuroshio Extension (KE) and subarctic frontal zone (SAFZ) is associated with the overall cooling/warming over the KE and SAFZ region (KE–SAFZ mode). It appears, however, that changes in KE strength induce different signs of thermal anomalies to the south and north of the KE, not extended to the SAFZ (KE mode), possibly contributing to noncoherent variability between the KE and SAFZ. Thus, the KE and SAFZ are dependent on each other in the context of the KE–SAFZ mode, while the KE is independent of the SAFZ in terms of the KE mode. This intricate relationship is associated with different linkages to atmospheric variability; the KE–SAFZ mode exhibits a relatively fast response to the large-scale wind stress curl forcing in the NP, whereas the KE mode is related to a delayed response to the atmospheric forcing via jet-trapped baroclinic Rossby wave propagation. It is suggested that further knowledge of the underlying mechanisms of the two modes would contribute to understanding ocean–atmosphere feedback as well as potential predictability over the western boundary current region in the NP.

Tropical Cyclone Changes in the Western North Pacific in a Global Warming Scenario

2007 ◽  
Vol 20 (11) ◽  
pp. 2378-2396 ◽  
Author(s):  
Markus Stowasser ◽  
Yuqing Wang ◽  
Kevin Hamilton
Keyword(s):  
Global Warming ◽  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Surface Air Temperature ◽  
Good Representation ◽  
Climate System Model

Abstract The influence of global warming on the climatology of tropical cyclones in the western North Pacific basin is examined using the high-resolution International Pacific Research Center (IPRC) regional climate model forced by ocean temperatures and horizontal boundary fields taken from the NCAR Community Climate System Model version 2 (CCSM2) coupled global climate model. The regional model is first tested in 10 yr of simulation with boundary forcing taken from observations and is shown to produce a reasonably good representation of the observed statistics of tropical cyclone numbers and locations. The model was then run for 10 yr with forcing from a present-day control run of the CCSM2 and then for 10 yr with forcing fields taken from the end of a long run with 6 times the present-day atmospheric CO2 concentration. The global-mean surface air temperature warming in the perturbed run is 4.5 K, while the surface warming in the tropical western North Pacific is about 3 K. The results of these experiments reveal no statistically significant change in basinwide tropical cyclone numbers in the peak season from July to October in response to the CO2 increase. However, a pronounced and statistically significant increase in tropical cyclone occurrence in the South China Sea is found. While the basinwide total number of storms remains nearly unchanged in the warm climate, there is a statistically significant increase in the average strength of the cyclones and in the number of the storms in the strongest wind categories.

scholarly journals Role of the Indochina Peninsula Narrow Mountains in Modulating the East Asian–Western North Pacific Summer Monsoon

2016 ◽  
Vol 29 (12) ◽  
pp. 4445-4459 ◽  
Author(s):  
Chi-Hua Wu ◽  
Huang-Hsiung Hsu
Keyword(s):  
Summer Monsoon ◽  
North Pacific ◽  
Western North Pacific ◽  
Global Climate ◽  
Global Climate Model ◽  
East Asian ◽  
High Mountain ◽  
The Tibetan Plateau ◽  
Topographic Effects ◽  
Indochina Peninsula

Abstract Unrealistic topographic effects are generally incorporated in global climate simulations and may contribute significantly to model biases in the Asian monsoon region. By artificially implementing the Arakan Yoma and Annamese Cordillera—two south–north-oriented high mountain ranges on the coasts of the Indochina Peninsula—in a 1° global climate model, it is demonstrated that the proper representation of mesoscale topography over the Indochina Peninsula is crucial for realistically simulating the seasonality of the East Asian–western North Pacific (EAWNP) summer monsoon. Presence of the Arakan Yoma and Annamese Cordillera helps simulate the vertical coupling of atmospheric circulation over the mountain regions. In late May, the existence of the Arakan Yoma enhances the vertically deep southwesterly flow originating from the trough over the Bay of Bengal. The ascending southwesterly flow converges with the midlatitude jet stream downstream in the southeast of the Tibetan Plateau and transports moisture across the Indochina Peninsula to East Asia. The existence of the Annamese Cordillera helps the northward lower-tropospheric moisture transport over the South China Sea into the mei-yu–baiu system, and the leeside troughing effect of the mountains likely contributes to the enhancement of the subtropical high to the east. Moreover, the eastward propagation of wave energy from central Asia to the EAWNP suggests a dynamical connection between the midlatitude westerly perturbation and mei-yu–baiu. Including the Annamese Cordillera also strengthens a Pacific–Japan (PJ) pattern–like perturbation in late July by enhancing the cyclonic circulation (i.e., monsoon trough) in the lower-tropospheric western North Pacific. This suggests the contribution of the mountain effects to the intrinsic variability of the summer monsoon in the EAWNP.

scholarly journals Metabolism and chemical composition of mesopelagic ostracods in the western North Pacific Ocean

2004 ◽  
Vol 61 (4) ◽  
pp. 535-541 ◽  
Author(s):  
Hideki Kaeriyama ◽  
Tsutomu Ikeda
Keyword(s):  
Oxygen Consumption ◽  
North Pacific ◽  
Western North Pacific ◽  
North Pacific Ocean ◽  
Standing Stock ◽  
Oyashio Region ◽  
Mesopelagic Zone ◽  
Poc Flux ◽  
Consumption Rates

Abstract Oxygen consumption rates and bodily elemental composition (carbon (C) and nitrogen (N)) were determined on three dominant ostracods (Discoconchoecia pseudodiscophora, Orthoconchoecia haddoni, and Metaconchoecia skogsbergi) from the mesopelagic zone of the Oyashio region. Specific oxygen consumption rates of the three species at near in situ temperature (3°C) were similar (0.39 μl O2 mg DW−1 h−1), but bodily C composition and C:N ratios of D. pseudodiscophora were significantly higher than those of the other two species. Metabolic comparison in terms of “daily body C loss” or “adjusted metabolic rate” revealed that metabolic rates of the ostracods are 0.3–0.4 times those of other zooplankton at comparable temperature conditions. The present results were combined with standing stock data of each ostracod in the Oyashio region to estimate their POC ingestion. Our calculation indicates annual ingestion by the ostracods to be 875 mgC m−2 yr−1, which equates to 3.7% of annual POC flux reaching 200–600-m depth (mid-point: 400-m depth) in this region.

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