Satellite-measured temporal and spatial variability of the Tokachi River plume

Tukimat Lihan, Sei Ichi Saitoh, Takahiro Iida, Toru Hirawake, Kohji Iida

Research output: Contribution to journalArticle

34 Citations (Scopus)

Abstract

River plumes have important effects on marine ecosystems. Variation in the extent and dispersal of river plumes is often associated with river discharge, wind characteristics and ocean circulation. The objectives of this study were to identify the Tokachi River plume by satellite, determine its relationship with river discharge and clarify its temporal and spatial dynamics. SeaWiFS multispectral satellite data (normalized water-leaving radiance: nLw) with 1.1 km spatial resolution were used to determine the spatial and temporal variability of the plume during 1998-2002. Supervised maximum likelihood classification using six channels of nLw at 412, 443, 490, 510, 555 and 670 nm with each band's spectral signature statistic was used to define classes of surface water and to estimate the plume area. Supervised maximum likelihood classification separated three to four classes of coastal water based on optical characteristics as a result of wind stress events. The satellite-observed plume area was correlated with the amount of river discharge from April to October. The plume distribution patterns were influenced by wind direction and magnitude, the occurrences of a near-shore eddy field and surface currents. Empirical orthogonal function (EOF) was used to express the spatial and temporal variability of the plume using anomalies of nLw(555) monthly averaged images. The first mode (44% of variance) showed the turbid plume distribution resulting from re-suspension by strong wind mixing along the coast during winter. This mode also showed the plume was distributed along-shelf direction in spring to early autumn. The second mode (17% of variance) showed spring pattern across-shelf direction. EOF analysis also explained the interannual variability of the plume signature, which might have been affected by the flow of the Oyashio Current and the occurrence of a near-shore eddy field.

Original languageEnglish
Pages (from-to)237-249
Number of pages13
JournalEstuarine, Coastal and Shelf Science
Volume78
Issue number2
DOIs
Publication statusPublished - 20 Jun 2008
Externally publishedYes

Fingerprint

river plume
plume
rivers
river discharge
eddy
wind direction
coastal water
remote sensing
SeaWiFS
surface water
statistics
oceans
resuspension
wind stress
marine ecosystem
radiance
autumn
coasts
satellite data
spatial resolution

Keywords

  • EOF
  • interannual variability
  • seasonal variation
  • SeaWiFS
  • Tokachi River plume

ASJC Scopus subject areas

  • Aquatic Science
  • Oceanography

Cite this

Satellite-measured temporal and spatial variability of the Tokachi River plume. / Lihan, Tukimat; Saitoh, Sei Ichi; Iida, Takahiro; Hirawake, Toru; Iida, Kohji.

In: Estuarine, Coastal and Shelf Science, Vol. 78, No. 2, 20.06.2008, p. 237-249.

Research output: Contribution to journalArticle

Lihan, Tukimat ; Saitoh, Sei Ichi ; Iida, Takahiro ; Hirawake, Toru ; Iida, Kohji. / Satellite-measured temporal and spatial variability of the Tokachi River plume. In: Estuarine, Coastal and Shelf Science. 2008 ; Vol. 78, No. 2. pp. 237-249.
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