Different trajectory patterns of ocean surface drifters modulated by near-inertial oscillations

Zheng, Yuhang, Wu, Wei, Wang, Minyang, Zhang, Yuhong and Du, Yan (2024) Different trajectory patterns of ocean surface drifters modulated by near-inertial oscillations. Environmental Research Letters, 19 (10). ISSN 1748-9326

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Abstract

Near-inertial oscillations (NIOs) are widely observed dynamic motions in the global ocean, with a frequency related to earth’s rotation. Using a particle trajectory model, we found the combined influence of mesoscale eddies and NIOs could produce distinctive flower-like trajectories, which are a special case of near-inertial trajectories and were observed by surface drifters released within an anticyclone eddy in the South China Sea in 2021. The energy budget indicates that wind and geostrophic eddy currents are crucial in generating near-inertial energy during the flower-like trajectories. Furthermore, the particle trajectory model revealed variations in periods and widths of the near-inertial trajectory with latitudes. The width of near-inertial trajectories can exceed 8 km in the near-equatorial region and reach 3-6 km in the mid-latitude region (20°-50°). The ratios of near-inertial velocity to background velocity, defined as near-inertial trajectory shape index (NITSIs), lead to arc-shaped (0.5 < NITSI < 1.0), overlapping semi-circular (NITSI > 1.0), and near-circular trajectories (NITSI ≫ 1.0). Globally, approximately 1/3 of the drifters’ lifespan featured clear near-inertial trajectories, with a significant presence in most middle latitudes and the largest NITSI in the north Pacific westerly. These findings highlight the importance of NIOs and suggest their substantial impact on local surface matter distribution, trajectory prediction, and marine rescue operations.

Item Type:	Article
Additional Information:	Data availability statement: Data sets of drifters deployed in 2021 cruise for this manuscript are available at the National Earth System Science Data Center (www.geodata.cn/main/face_science_detail?typeName=face_science&guid=39099061696594). GDP drifter data are provided by AMOL, available at www.aoml.noaa.gov/phod/gdp/hourly_data.php. SLA data are obtained from CMEMS website (https://data.marine.copernicus.eu/product/SEALEVEL_GLO_PHY_L4_MY_008_047/services). ERA5 wind data is provided by ECMWF, downloaded from https://cds.climate.copernicus.eu/cdsapp#!/dataset/reanalysis-era5-single-levels?tab=form. CSFv2 wind data and HYCOM data are obtained from the U. S. Global Ocean Data Assimilation Experiment website www.hycom.org/dataserver/ncep-cfsv2 and www.hycom.org/dataserver/gofs-3pt1/analysis. The WOA2018 climatological monthly mean mixed layer depth data are available at www.ncei.noaa.gov/access/world-ocean-atlas-2018/bin/woa18.pl.All data that support the findings of this study are included within the article (and any supplementary files).
Uncontrolled Keywords:	drifter trajectories,mesoscale eddy,near-inertial oscillations,near-inertial trajectory shape index,public health, environmental and occupational health,environmental science(all),renewable energy, sustainability and the environment ,/dk/atira/pure/subjectarea/asjc/2700/2739
Faculty \ School:	Faculty of Science > School of Environmental Sciences
Related URLs:	http://www.scopus.com/inward/record.url?...
Depositing User:	LivePure Connector
Date Deposited:	09 Dec 2025 14:30
Last Modified:	14 Dec 2025 07:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/101348
DOI:	10.1088/1748-9326/ad7745

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