Spreading of warm water from the Kuroshio Extension into the Perturbed Area

Sainz-Trápaga, Susana; Sugimoto, Takashige

doi:10.1007/bf02751701

Cited by 19 publications

(7 citation statements)

References 15 publications

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“…In June, the Oyashio and Kuroshio fronts are defined by the 5°C isotherm at 100 m depth and 14°C isotherm at 200 m depth, respectively. 23,24 These observations together with closely located towing sites suggest that oceanographic conditions for all tows were almost identical and located within the KOTZ.…”

Section: Resultsmentioning

confidence: 87%

Night-time vertical distribution and abundance of small epipelagic and mesopelagic fishes in the upper 100 m layer of the Kuroshio-Oyashio Transition Zone in Spring

Yatsu

Sassa²,

Moku

et al. 2005

Fisheries Sci

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In order to simultaneously compare vertical distributions of small pelagic fishes and mesopelagic fishes during the night in the upper 100 m, one oblique and 11 horizontal tows of largesized (opening area 480 m 2 ) trawl operations were conducted at different depths in the KuroshioOyashio Transition Zone during 20-22 May 1995. While Japanese sardine Sardinops melanostictus and Japanese anchovy Engraulis japonicus were concentrated in the upper 20 m, mackerels Scomber spp. were collected uniformly in the upper 80 m layer. Myctophid fishes Ceratoscopelus warmingii, Diaphus kuroshio, Diogenichthys atlanticus, Myctophum asperum, Notoscopelus spp. mostly N. resplendens, and Symbolophorus californiensis, a gempylid Nealotus tripes, a microstomatid Lipolagus ochotensis and a phosichthyid Vinciguerria nimbaria were dominant components of mesopelagic fishes that ascended to the upper 100 m layer at night, where these mesopelagic fishes concentrated at depths of 20-80 m. In the upper 20 m layer, Japanese anchovy comprised 60% of the total wet weight of all fishes followed by D. atlanticus (3%), C. warmingii (2%) and S. californiensis (2%). Juvenile myctophids were dominant in the upper 20 m layer compared to deeper layers.

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Section: Resultsmentioning

confidence: 87%

Night-time vertical distribution and abundance of small epipelagic and mesopelagic fishes in the upper 100 m layer of the Kuroshio-Oyashio Transition Zone in Spring

Yatsu

Sassa²,

Moku

et al. 2005

Fisheries Sci

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“…Both Pickart et al (1999) and Kuroshio branching observations by Sainz-Tra Âpaga and Sugimoto (1998Sugimoto ( , 1999) support this assumption. Over 60% of these drifters move down the large-scale dynamic height ®eld as they meander out into the Paci®c.…”

Section: Large-scale Branchingmentioning

confidence: 81%

“…This assumes the branching and ring formation involve a similar thickness of¯uid. Both Pickart et al (1999) and Kuroshio branching observations by Sainz-Tra Âpaga and Sugimoto (1998Sugimoto ( , 1999) support this assumption. Subtracting the streamer estimate above gives a branching estimate of 2.6´10 14 m 3 year ±1 .…”

Section: Large-scale Branchingmentioning

confidence: 81%

“…While the highly time-dependent transfers of¯uid under in¯uence of rings clearly make a major contribution to exchanges of¯uid into and out of the transition zone, there is evidence to reconsider the older picture of current bifurcations (Sainz-Tra Âpaga and Sugimoto, 1998). A similar reconsideration in the Gulf Stream extension involves reconsiderations of Fuglister's (1951) (see also McLellan, 1957;Stommel, 1965) discussion of how to contour the Gulf Stream (Pickart et al, 1999).…”

Section: Early Depictions Of Both the Kuroshio And Gulfmentioning

confidence: 99%

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Biophysical dynamics of western transition zones: a preliminary synthesis

Olson

2001

Fisheries Oceanography

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The nature of the western portions of the biogeographic temperate or transition zones in the North Pacific and North Atlantic is reviewed. The physical transport of nutrients and biomass into them from the Kuroshio and Gulf Stream as well as from the poleward sides are estimated. The conclusion is that the upwelling in the two western boundary currents makes the largest contribution to the nutrient and biomass fluxes into these transition zones. A conservative estimate of the amount of upwelled fluid is derived from absolute velocity sections in the Gulf Stream. The estimate suggests that upwelling into the euphotic zone exceeds 2 × 106 m3 s–1. This implies that upwelling in these western boundary currents matches or exceeds that in eastern boundary currents such as the California Current. The two western boundary regimes have very different poleward situations. The Oyashio extension flows parallel to the Kuroshio and is a deep current. The North Atlantic Shelf Front flow is to the west where it is ultimately entrained into the edge of the Gulf Stream. There does not seem to be any tendency for this to occur in the Kuroshio. Despite these differences in the northern and western boundaries, the two transition zones are similar with large amplitude meanders, anticyclonic rings and streamers dominating their physical structure. The physical features responsible for the transfer of materials from the boundary current extensions into the transition zones are similar in both systems. Ring formation contributes only ˜ 10% of the transfer, while ring‐induced streamers contribute 30%. The rest of the transport is contributed by branching of the boundary current front. Both currents have well developed secondary fronts consisting of subtropical surface water pulled into the transition zone. Biologically, the upwelling in both western boundary currents leads to a biomass maximum along the boundary in both secondary producers (copepods) and in small pelagic fish. In the Kuroshio, the latter are the Japanese sardine, Sardinops melanostictus, that spawn in the Kuroshio and then enter the transition zone for the summer and fall months. In the Gulf Stream, the dominate species are menhaden, Brevoortia tyrannus and B. smithi. These species make use of the coastal environments of North America and although the adults spawn in the Gulf Stream, they are not thought to play a major role in the Slope Water, transition zone. The similar differences in the use of the Kuroshio and the Gulf Stream ecosystems occurs in the behaviour of bluefin tuna, squid and other large pelagics. The Gulf Stream system also lacks an equivalent to Pacific saury, Cololabis saira. The biology therefore is at least subtly different, with saury and sardines being replaced by mid‐water fish in the North Atlantic. A fuller comparison of the biology with quantitative methods in both systems should be encouraged.

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“…[] suggested that small meanders are important to the generation of streamers. Indeed, the KE emits its warm water to the north near the first crest of the quasi‐stationary KE meander with a period of 20–40 days [ Sainz‐Trapaga and Sugimoto , ], which is roughly consistent with the small meander periods of 6–40 days observed from the KESS array [ Tracey et al ., ]. Warm‐water streamers are important routes for the northward migration of warm‐water fish toward the feeding area north of the KE [ Sugimoto and Tameishi , ] and have also been considered a possible source of a quasi‐stationary jet flowing northeastward across the Kuroshio‐Oyashio transition area [ Isoguchi et al ., ; Wagawa et al ., ].…”

Section: Introductionmentioning

confidence: 99%

Small meanders of the Kuroshio Extension and associated northward spreading of warm water: Three‐vessel simultaneous observations and an eddy‐resolving ocean model simulation

et al. 2016

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Small meanders of the Kuroshio Extension (KE) were examined in the three vessel simultaneous observations carried out across the KE along 143°E between 2 and 7 July 2012 and the hindcast simulation by a high‐resolution ocean model for the Earth Simulator (OFES). The observations captured the crest of the small meander that passed 143°E. Behind the meander crest, the meander showed the northward separation of the front from the meandering jet. It was suggested that the meander spread the low‐density KE water to the north above the main pycnocline there. The OFES showed similar characteristics of small meanders. We focused on three major small meanders. In the upstream KE region west of 143°E, these meanders were subject to northeastward ageostrophic advection, by which the low‐density KE water was carried to the north and their fronts moved away from the KE jet above the main pycnocline. This resulted in the KE water and the front extending to the west behind the crest of the downstream‐propagating meanders. This feature was particularly obvious for the two cases of the meander and was consistent with the observations. The displaced front formed a shallow geostrophic jet to the north of the main KE jet, which induced geostrophic advection along the jet and advected the front further northward and downstream near the crest of the meandering front. The KE water spread by the small meanders then mostly evolved into warm core rings or warm streamers.

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Spreading of warm water from the Kuroshio Extension into the Perturbed Area

Cited by 19 publications

References 15 publications

Night-time vertical distribution and abundance of small epipelagic and mesopelagic fishes in the upper 100 m layer of the Kuroshio-Oyashio Transition Zone in Spring

Night-time vertical distribution and abundance of small epipelagic and mesopelagic fishes in the upper 100 m layer of the Kuroshio-Oyashio Transition Zone in Spring

Biophysical dynamics of western transition zones: a preliminary synthesis

Small meanders of the Kuroshio Extension and associated northward spreading of warm water: Three‐vessel simultaneous observations and an eddy‐resolving ocean model simulation

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