Articles | Volume 22, issue 4
https://doi.org/10.5194/os-22-2449-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/os-22-2449-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
17 Aug 2026
Research article |
| 17 Aug 2026
| 17 Aug 2026
Intraseasonal variability and eddy-induced structural modulation of the North Pacific intermediate water revealed by multi-mooring observations
Qiang Ren
Key Laboratory of Ocean Observation and Forecasting and Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
Laboratory for Ocean Dynamics and Climate, Qingdao Marine Science and Technology Center, Qingdao, China
Yansong Liu
Key Laboratory of Ocean Observation and Forecasting and Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
Laboratory for Ocean Dynamics and Climate, Qingdao Marine Science and Technology Center, Qingdao, China
Yansheng Zhang
National Marine Data and Information Service, Tianjing, China
Shumin Tu
Laboratory of Low Frequency Electromagnetic Communication Technology with the WMCRI, CSSC, Wuhan, China
Wei Huang
Laboratory of Low Frequency Electromagnetic Communication Technology with the WMCRI, CSSC, Wuhan, China
Feng Nan
Key Laboratory of Ocean Observation and Forecasting and Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
Laboratory for Ocean Dynamics and Climate, Qingdao Marine Science and Technology Center, Qingdao, China
College of Marine Sciences, University of Chinese Academy of Sciences, Qingdao, China
Ran Wang
Key Laboratory of Ocean Observation and Forecasting and Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
Laboratory for Ocean Dynamics and Climate, Qingdao Marine Science and Technology Center, Qingdao, China
Xinyuan Diao
Key Laboratory of Ocean Observation and Forecasting and Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
Laboratory for Ocean Dynamics and Climate, Qingdao Marine Science and Technology Center, Qingdao, China
College of Marine Sciences, University of Chinese Academy of Sciences, Qingdao, China
Jianfeng Wang
Key Laboratory of Ocean Observation and Forecasting and Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
Laboratory for Ocean Dynamics and Climate, Qingdao Marine Science and Technology Center, Qingdao, China
Xinchuang Liu
Key Laboratory of Ocean Observation and Forecasting and Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
Laboratory for Ocean Dynamics and Climate, Qingdao Marine Science and Technology Center, Qingdao, China
Zifei Chen
CORRESPONDING AUTHOR
Key Laboratory of Ocean Observation and Forecasting and Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
Laboratory for Ocean Dynamics and Climate, Qingdao Marine Science and Technology Center, Qingdao, China
Fei Yu
CORRESPONDING AUTHOR
Key Laboratory of Ocean Observation and Forecasting and Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
Laboratory for Ocean Dynamics and Climate, Qingdao Marine Science and Technology Center, Qingdao, China
College of Marine Sciences, University of Chinese Academy of Sciences, Qingdao, China
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EGUsphere, https://doi.org/10.5194/egusphere-2026-1351, https://doi.org/10.5194/egusphere-2026-1351, 2026
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This study examines two near-inertial wave events during winter storms using subsurface mooring observations and reanalysis data. Wind energy input during the first storm was about three times that during the second, but the observed near-inertial energy was similar. Eddies and modal contents are important factors. The low modes dominates the first event, while the high modes dominates the second event. These factors together affect the wintertime interior mixing.
Ren Qiang, Yansong Liu, Feng Nan, Ran Wang, Xinyuan Diao, Fei Yu, Zifei Chen, Jianfeng Wang, and Xinchuan Liu
EGUsphere, https://doi.org/10.5194/egusphere-2024-3227, https://doi.org/10.5194/egusphere-2024-3227, 2024
Preprint archived
Short summary
Short summary
In this study, direct measurements from three moorings are utilized to reveal the intraseasonal variability of the North Pacific Intermediate Water in different regions for 60–80 days. It was found that the intraseasonal variation of NPIW is mainly caused by mesoscale eddies. Understanding these dynamics is critical for assessing the NPIW's response to climate change and its implications for the global carbon cycle and marine ecosystems.
Cited articles
Auad, G., Kennett, J. P., and Miller, A. J.: North Pacific Intermediate Water response to a modern climate warming shift, J. Geophys. Res.-Oceans, 108, 3349, https://doi.org/10.1029/2003JC001987, 2003.
Bingham, F. M. and Lukas, R.: The distribution of intermediate water in the western equatorial Pacific during January-February 1986, Deep-Sea Res. Pt. I, 42, 1545–1573, https://doi.org/10.1016/0967-0637(95)00064-D, 1995.
Chelton, D. B., Schlax, M. G., Samelson, R. M., and de Szoeke, R. A.: Global observations of large oceanic eddies, Geophys. Res. Lett., 34, L15606, https://doi.org/10.1029/2007GL030812, 2007.
Chelton, D. B., Gaube, P., Schlax, M. G., Early, J. J., and Samelson, R. M.: The influence of nonlinear mesoscale eddies on near-surface oceanic chlorophyll, Science, 334, 328–332, https://doi.org/10.1126/science.1208897, 2011a.
Chelton, D. B., Schlax, M. G., and Samelson, R. M.: Global observations of nonlinear mesoscale eddies, Prog. Oceanogr., 91, 167–216, https://doi.org/10.1016/j.pocean.2011.01.002, 2011b.
E.U. Copernicus Marine Service Information: Global Ocean Gridded L4 Sea Surface Heights and Derived Variables Reprocessed Copernicus Climate Service (SEALEVEL_GLO_PHY_CLIMATE_L4_MY_008_057), Marine Data Store (MDS) [data set], https://doi.org/10.48670/moi-00145, 2026a.
E.U. Copernicus Marine Service Information: Multi Observation Global Ocean 3D Temperature Salinity Height Geostrophic Current and MLD (MULTIOBS_GLO_PHY_TSUV_3D_MYNRT_015_012), Marine Data Store (MDS) [data set], https://doi.org/10.48670/moi-00052, 2026b.
Fujii, Y., Nakano, T., Usui, N., Matsumoto, S., Tsujino, H., and Kamachi, M.: Pathways of the North Pacific Intermediate Water identified through the tangent linear and adjoint models of an ocean general circulation model, J. Geophys. Res.-Oceans, 118, 2035–2051, https://doi.org/10.1002/jgrc.20094, 2013.
George, T. M., Manucharyan, G., and Thompson, A. F.: Deep learning to infer eddy heat fluxes from sea surface height patterns of mesoscale turbulence, Nat. Commun., 12, 800, https://doi.org/10.1038/s41467-020-20779-9, 2021.
Gong, X., Lembke-Jene, L., Lohmann, G., Knorr, G., Tiedemann, R., Zou, J., and Shi, X.: Enhanced North Pacific deep-ocean stratification by stronger intermediate water formation during Heinrich Stadial 1, Nat. Commun., 10, 656, https://doi.org/10.1038/s41467-019-08606-2, 2019.
Gordon, A. L. and Fine, R. A.: Pathways of water between the Pacific and Indian oceans in the Indonesian seas, Nature, 379, 146–149, https://doi.org/10.1038/379146a0, 1996.
Guinehut, S., Dhomps, A.-L., Larnicol, G., and Le Traon, P.-Y.: High resolution 3-D temperature and salinity fields derived from in situ and satellite observations, Ocean Sci., 8, 845–857, https://doi.org/10.5194/os-8-845-2012, 2012.
Hansell, D. A., Carlson, C. A., and Suzuki, Y.: Dissolved organic carbon export with North Pacific Intermediate Water formation, Global Biogeochem. Cy., 16, 1007, https://doi.org/10.1029/2000GB001361, 2002.
Hausmann, U., McGillicuddy Jr., D. J., and Marshall, J.: Observed mesoscale eddy signatures in Southern Ocean surface mixed-layer depth, J. Geophys. Res.-Oceans, 122, 617–635, https://doi.org/10.1002/2016JC012225, 2017.
Kashino, Y., Aoyama, M., Kawano, T., Hendiarti, N., Syaefudin, Anantasena, Y., Muneyama, K., and Watanabe, H.: The water masses between Mindanao and New Guinea, J. Geophys. Res.-Oceans, 101, 12391–12400, https://doi.org/10.1029/95JC03797, 1996.
Kashino, Y., Watanabe, H., Herunadi, B., Aoyama, M., and Hartoyo, D.: Current variability at the Pacific entrance of the Indonesian Throughflow, J. Geophys. Res.-Oceans, 104, 11021–11035, https://doi.org/10.1029/1999JC900033, 1999.
Li, Z., England, M. H., and Groeskamp, S.: Recent acceleration in global ocean heat accumulation by mode and intermediate waters, Nat. Commun., 14, 6888, https://doi.org/10.1038/s41467-023-42468-z, 2023.
Martínez-Moreno, J., Hogg, A. M., England, M. H., Constantinou, N. C., Kiss, A. E., and Morrison, A. K.: Global changes in oceanic mesoscale currents over the satellite altimetry record, Nat. Clim. Change, 11, 397–403, https://doi.org/10.1038/s41558-021-01006-9, 2021.
Masuda, S., Awaji, T., Sugiura, N., Ishikawa, Y., Baba, K., Horiuchi, K., and Komori, N.: Improved estimates of the dynamical state of the North Pacific Ocean from a 4-dimensional variational data assimilation, Geophys. Res. Lett., 30, 1868, https://doi.org/10.1029/2003GL017604, 2003.
Masujima, M. and Yasuda, I.: Distribution and modification of North Pacific Intermediate Water around the Subarctic Frontal Zone east of 150° E, J. Phys. Oceanogr., 39, 1462–1474, https://doi.org/10.1175/2008JPO3919.1, 2009.
Mensah, V., Jan, S., Chang, M.-H., and Yang, Y. J.: Intraseasonal to seasonal variability of the intermediate waters along the Kuroshio path east of Taiwan, J. Geophys. Res.-Oceans, 120, 5473–5489, https://doi.org/10.1002/2015JC010768, 2015.
Mulet, S., Rio, M.-H., Mignot, A., Guinehut, S., and Morrow, R.: A new estimate of the global 3-D geostrophic ocean circulation based on satellite data and in-situ measurements, Deep-Sea Res. Pt. II, 77–80, 70–81, https://doi.org/10.1016/j.dsr2.2012.04.012, 2012.
Nakanowatari, T., Mitsudera, H., Motoi, T., Ishikawa, I., Ohshima, K. I., and Wakatsuchi, M.: Multidecadal-scale freshening at the salinity minimum in the western part of North Pacific: Importance of wind-driven cross-gyre transport of subarctic water to the subtropical gyre, J. Phys. Oceanogr., 45, 988–1008, https://doi.org/10.1175/JPO-D-13-0274.1, 2015.
Nishioka, J., Obata, H., Ogawa, H., Ono, K., Yamashita, Y., Lee, K., Takeda, S., and Yasuda, I.: Subpolar marginal seas fuel the North Pacific through the intermediate water at the termination of the global ocean circulation, P. Natl. Acad. Sci. USA, 117, 12665–12673, https://doi.org/10.1073/pnas.2000658117, 2020.
Ohkushi, K., Itaki, T., and Nemoto, N.: Last Glacial-Holocene change in intermediate-water ventilation in the northwestern Pacific, Quaternary Sci. Rev., 22, 1477–1484, https://doi.org/10.1016/S0277-3791(03)00082-9, 2003.
Ohshima, K. I., Nakanowatari, T., Riser, S., and Wakatsuchi, M.: Seasonal variation in the in- and outflow of the Okhotsk Sea with the North Pacific, Deep-Sea Res. Pt. II, 57, 1247–1256, https://doi.org/10.1016/j.dsr2.2009.12.012, 2010.
Qiu, B.: Why is the spreading of the North Pacific Intermediate Water confined on density surfaces around σθ= 26.8?, J. Phys. Oceanogr., 25, 168–180, https://doi.org/10.1175/1520-0485(1995)025<0168:WITSOT>2.0.CO;2, 1995.
Qiu, B. and Chen, S.: Eddy-induced heat transport in the subtropical North Pacific from Argo, TMI, and altimetry measurements, J. Phys. Oceanogr., 35, 458–473, https://doi.org/10.1175/JPO2696.1, 2005.
Qiu, B. and Chen, S.: Effect of decadal Kuroshio Extension jet and eddy variability on the modification of North Pacific Intermediate Water, J. Phys. Oceanogr., 41, 503–515, https://doi.org/10.1175/2010JPO4575.1, 2011.
Reagan, J. R., Boyer, T. P., García, H. E., Locarnini, R. A., Baranova, O. K., Bouchard, C., Cross, S. L., Mishonov, A. V., Paver, C. R., Seidov, D., Wang, Z., and Dukhovskoy, D.: World Ocean Atlas 2023, NOAA National Centers for Environmental Information [data set], https://doi.org/10.25921/va26-hv25, 2023.
Ren, Q.: Fixed-point salinity observation dataset in the western Pacific Ocean, Marine Science Data Center, Chinese Academy of Sciences [data set], https://doi.org/10.12157/IOCAS.20260710.001, 2026.
Ren, Q., Yu, F., Nan, F., Wang, J., and Xu, A.: Intraseasonal variability of the Kuroshio east of Taiwan, China, observed by subsurface mooring during 2016–2017, J. Oceanol. Limnol., 38, 1408–1420, https://doi.org/10.1007/s00343-020-9286-3, 2020.
Ren, Q., Yu, F., Nan, F., Li, Y., Wang, J., Liu, Y., and Chen, Z.: Effects of mesoscale eddies on intraseasonal variability of intermediate water east of Taiwan, Sci. Rep., 12, 9182, https://doi.org/10.1038/s41598-022-13274-2, 2022.
Richardson, P. L.: Eddy kinetic energy in the North Atlantic from surface drifters, J. Geophys. Res.-Oceans, 88, 4355–4367, https://doi.org/10.1029/JC088iC07p04355, 1983.
Robinson, A. R. and Leslie, W. G.: Estimation and prediction of oceanic eddy fields, Prog. Oceanogr., 14, 485–510, https://doi.org/10.1016/0079-6611(85)90024-2, 1985.
Solomon, A., McCreary Jr., J. P., Kleeman, R., and Klinger, B. A.: Interannual and decadal variability in an intermediate coupled model of the Pacific region, J. Climate, 16, 383–405, https://doi.org/10.1175/1520-0442(2003)016<0383:IADVIA>2.0.CO;2, 2003.
Sugimoto, S.: Decreasing wintertime mixed layer depth in the northwestern North Pacific subtropical gyre, Geophys. Res. Lett., 49, e2021GL095091, https://doi.org/10.1029/2021GL095091, 2022.
Talley, L. D.: Distribution and formation of North Pacific Intermediate Water, J. Phys. Oceanogr., 23, 517–537, https://doi.org/10.1175/1520-0485(1993)023<0517:DAFONP>2.0.CO;2, 1993.
Talley, L. D., Nagata, Y., Fujimura, M., Iwao, T., Kono, T., Inagake, D., Hirai, M., and Okuda, K.: North Pacific Intermediate Water in the Kuroshio/Oyashio Mixed Water Region, J. Phys. Oceanogr., 25, 475–501, https://doi.org/10.1175/1520-0485(1995)025<0475:NPIWIT>2.0.CO;2, 1995.
Thoppil, P. G., Richman, J. G., and Hogan, P. J.: Energetics of a global ocean circulation model compared to observations, Geophys. Res. Lett., 38, L15607, https://doi.org/10.1029/2011GL048347, 2011.
Tsunogai, S.: The western North Pacific playing a key role in global biogeochemical fluxes, J. Oceanogr., 58, 245–257, https://doi.org/10.1023/A:1015805607724, 2002.
Ueno, H. and Yasuda, I.: Intermediate water circulation in the North Pacific subarctic and northern subtropical regions, J. Geophys. Res.-Oceans, 108, 3348, https://doi.org/10.1029/2002JC001372, 2003.
Van Scoy, K. A. and Druffel, E. R. M.: Ventilation and transport of thermocline and intermediate waters in the northeast Pacific during recent El Niños, J. Geophys. Res.-Oceans, 98, 18083–18088, https://doi.org/10.1029/93JC01797, 1993.
Waite, A. M., Stemmann, L., Guidi, L., Calil, P. H. R., Hogg, A. M. C., Feng, M., Thompson, P. A., Picheral, M., and Gorsky, G.: The wineglass effect shapes particle export to the deep ocean in mesoscale eddies, Geophys. Res. Lett., 43, 9791–9800, https://doi.org/10.1002/2015GL066463, 2016.
Wang, F., Song, L., Li, Y., Liu, C., Wang, J., Lin, P., Yang, G., Zhao, J., Diao, X., Zhang, D., and Hu, D.: Semiannually alternating exchange of intermediate waters east of the Philippines, Geophys. Res. Lett., 43, 7059–7065, https://doi.org/10.1002/2016GL069323, 2016.
Wunsch, C. and Ferrari, R.: Vertical mixing, energy, and the general circulation of the oceans, Annu. Rev. Fluid Mech., 36, 281–314, https://doi.org/10.1146/annurev.fluid.36.050802.122121, 2004.
Wyrtki, K., Magaard, L., and Hager, J.: Eddy energy in the oceans, J. Geophys. Res., 81, 2641–2646, https://doi.org/10.1029/JC081i015p02641, 1976.
Yasuda, I.: The origin of the North Pacific Intermediate Water, J. Geophys. Res.-Oceans, 102, 893–909, https://doi.org/10.1029/96JC02938, 1997.
Yasuda, I.: North Pacific Intermediate Water: Progress in SAGE (SubArctic Gyre Experiment) and related projects, J. Oceanogr., 60, 385–395, https://doi.org/10.1023/B:JOCE.0000038344.25081.42, 2004.
Yin, Y., Lin, X., He, R., and Hou, Y.: Impact of mesoscale eddies on Kuroshio intrusion variability northeast of Taiwan, J. Geophys. Res.-Oceans, 122, 3021–3040, https://doi.org/10.1002/2016JC012263, 2017.
You, Y.: The pathway and circulation of North Pacific Intermediate Water, Geophys. Res. Lett., 30, 2291, https://doi.org/10.1029/2003GL018561, 2003.
Yuan, D., Yin, X., Li, X., Corvianawatie, C., Wang, Z., Li, Y., Yang, Y., Hu, X., Wang, J., Tan, S., Surinati, D., Purwandana, A., Wardana, A. K., Ismail, M. F. A., Budiman, A. S., Bayhaqi, A., Avianto, P., Santoso, P. D., Kusmanto, E., Dirhamsyah, Arifin, Z., and Pratt, L. J.: A Maluku Sea intermediate western boundary current connecting Pacific Ocean circulation to the Indonesian Throughflow, Nat. Commun., 13, 2093, https://doi.org/10.1038/s41467-022-29617-6, 2022.
Zhang, D., Lee, T. N., Johns, W. E., Liu, C.-T., and Zantopp, R.: The Kuroshio east of Taiwan: Modes of variability and relationship to interior ocean mesoscale eddies, J. Phys. Oceanogr., 31, 1054–1074, https://doi.org/10.1175/1520-0485(2001)031<1054:TKEOTM>2.0.CO;2, 2001.
Zhang, W., Xue, H., Chai, F., and Ni, Q.: Dynamical processes within an anticyclonic eddy revealed from Argo floats, Geophys. Res. Lett., 42, 2342–2350, https://doi.org/10.1002/2015GL063120, 2015.
Zhang, Z., Wang, W., and Qiu, B.: Oceanic mass transport by mesoscale eddies, Science, 345, 322-324, https://doi.org/10.1126/science.1252418, 2014.
Zhang, Z., Tian, J., Qiu, B., Zhao, W., Chang, P., Wu, D., and Wan, X.: Observed 3-D structure, generation, and dissipation of oceanic mesoscale eddies in the South China Sea, Sci. Rep., 6, 24349, https://doi.org/10.1038/srep24349, 2016.
Zhou, H., Liu, X., Chen, X., Wang, F., and Hu, D.: Intraseasonal variability of the North Equatorial Current bifurcation off the Philippines, J. Geophys. Res.-Oceans, 126, e2021JC017646, https://doi.org/10.1029/2021JC017646, 2021.
Short summary
This study reveals how mesoscale eddies modulate the North Pacific Intermediate Water (NPIW) using three long-term mooring observations. By introducing “intermediate water thickness” as a new structural indicator, it shows that eddies compress or expand the NPIW layer, producing 60–80-day intraseasonal variability. Thickness and salinity are strongly inversely related, providing the first quantitative evidence of eddy-induced structural changes in mid-depth waters.
This study reveals how mesoscale eddies modulate the North Pacific Intermediate Water (NPIW)...
