Skillful Multiyear Prediction of the Kuroshio and Gulf Stream Jets and Eddy Activity

Kido, Shoichiro; Nonaka, Masami; Miyazawa, Yasumasa

doi:10.1029/2023gl103705

Cited by 4 publications

(1 citation statement)

References 61 publications

(88 reference statements)

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“…Furthermore, marine industries may benefit from decadal predictions of biogeochemical states, as the decadal variability of the Kuroshio LM is expected to strengthen in the future due to the stronger decadal variability of the Kuroshio Extension (Joh et al, 2022) that is closely linked to the LM occurrence (Usui et al, 2013). Such biogeochemical implementation into a decadal ocean prediction system (e.g., Kido et al, 2022Kido et al, , 2023 has great potential in supporting long-term adaptation planning for future large meanders that may last longer than the ongoing record-breaking event, as demonstrated by our model simulations (Figure 2a).…”

Section: Discussionmentioning

confidence: 99%

Anomalous Nutricline Drives Marked Biogeochemical Contrasts During the Kuroshio Large Meander

et al. 2023

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The large meander (LM) of the Kuroshio western boundary current is well known to influence the local climate, fisheries, and aquaculture by greatly modulating regional heat transport, but its impact on biogeochemical processes remains unclear. Using a high‐resolution numerical ocean model and long‐term observational datasets, we show that the path of the Kuroshio south of Japan determines the extent of the shallow nutricline region, where winter convective mixing replenishes nutrient availability for subsequent blooms of phytoplankton during spring. During the LM phase, this mechanism triggers offshore phytoplankton blooms that can be twice as strong as those during the non‐large meander phase. In contrast, spring blooms are weaker in the nearshore region where the nutricline depth is deeper, which reduces the nutrient supply by winter convective mixing during the LM. The LM also modulates the spatial distributions of primary production, air‐sea carbon flux, and export production. Hence, the Kuroshio path variability has broader implications for marine ecosystems and biogeochemical cycles. The biogeochemical impacts of the Kuroshio LM exert bottom‐up control on regional marine ecosystems that may be disproportionate to its thermal effect, and therefore need to be assessed to understand the LM's overall impacts on fisheries and aquaculture.

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Section: Discussionmentioning

confidence: 99%

Anomalous Nutricline Drives Marked Biogeochemical Contrasts During the Kuroshio Large Meander

et al. 2023

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Exceptional Heat and Basin-Scale Connections in the Kuroshio-Oyashio Region in the Early 2020s

Minobe

2024

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This study investigates recent extreme conditions in the North Pacific, which began in the late 2010s and have intensified significantly by 2024, focusing on the Kuroshio-Oyashio region. The anomalies appear to have originated in the western North Pacific, linked to changes in the Kuroshio and Oyashio currents, while developments in the eastern North Pacific remained somewhat distinct. Sea surface temperature anomalies in the Kuroshio-Oyashio region have reached record-breaking levels, with deviations up to 6°C above the 1993–2022 average. Subsurface temperatures have also increased notably, accounting for 15.7% and 12.3% in the western and eastern North Pacific (28% combined) of the global ocean heat content increase in the 0–300 m layer between 2020s and 2010s. In the 2020s, the Kuroshio current extended northward to approximately 42°N along Japan’s coast, forming a loop-like pattern with a southward return flow, while the Kuroshio Extension in wider zonal extent also shifted northward. These oceanic anomalies are likely influenced by wind changes, with Sverdrup theory suggesting weakened subtropical gyres and a northward shift of the subtropical-subpolar gyre boundary. Further research is needed to fully understand, monitor, and predict these changes and their impacts on regional ecosystems.

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The international multi-system OSEs/OSSEs by the UN Ocean Decade Project SynObs and its early results

Fujii,

Remy,

Balmaseda

et al. 2024

Front. Mar. Sci.

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“Synergistic Observing Network for Ocean Prediction (SynObs)” was launched in 2022 as a project of the United Nations Decade of Ocean Science for Sustainable Development to evaluate the importance of ocean observation systems and co-design the future evolution of the ocean observing network. SynObs is currently leading the flagship OSEs/OSSEs, an internationally coordinated activity in which observing system experiments (OSEs) and observing system simulation experiments (OSSEs) are conducted using a variety of ocean and coupled atmosphere–ocean prediction systems to evaluate ocean observation impacts consistent across most prediction systems. The flagship OSEs/OSSEs comprises the ocean prediction (OP) OSEs for high-resolution ocean predictions, the subseasonal-to-seasonal (S2S) OSEs for long-term lead-time coupled ocean–atmosphere predictions, and the OP OSSEs for evaluating new and future observing systems. SynObs plans to use the results of the flagship OSEs to contribute to the reports on the ocean observing network design made by international organizations and projects. Here, we introduce this initiative, and we report on some initial results. Some observation impacts consistent across four ocean prediction systems are found by a preliminary analysis of the analysis runs for the OP OSEs. For example, impacts of the altimetry data on the assimilated sea surface height (SSH) field are generally large in the westerly boundary current regions and around Antarctic Circumpolar Currents where SSH has large variability but are small in the tropical regions, despite the relatively large SSH variability there. The analysis also indicates the possibility that there are some characteristic differences in the observation impacts between low-resolution and eddy-resolving ocean prediction systems. Although OSE outputs of only four ocean prediction systems are available now, we will make further investigation, adding OSE outputs of other prediction systems that will be submitted in the near future.

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Skillful Multiyear Prediction of the Kuroshio and Gulf Stream Jets and Eddy Activity

Cited by 4 publications

References 61 publications

Anomalous Nutricline Drives Marked Biogeochemical Contrasts During the Kuroshio Large Meander

Anomalous Nutricline Drives Marked Biogeochemical Contrasts During the Kuroshio Large Meander

Exceptional Heat and Basin-Scale Connections in the Kuroshio-Oyashio Region in the Early 2020s

The international multi-system OSEs/OSSEs by the UN Ocean Decade Project SynObs and its early results

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