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Do Strong Winds Impact Water Mass, Nutrient, and Phytoplankton Distributions in the Ice‐Free Canada Basin in the Fall?
Author(s) -
Nishino Shigeto,
Kawaguchi Yusuke,
Inoue Jun,
YamamotoKawai Michiyo,
Aoyama Michio,
Harada Naomi,
Kikuchi Takashi
Publication year - 2020
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1029/2019jc015428
Subject(s) - pycnocline , oceanography , phytoplankton , photic zone , environmental science , thermocline , water mass , water column , mixed layer , chlorophyll a , geology , atmospheric sciences , nutrient , chemistry , ecology , biology , biochemistry
In general, strong wind events can enhance ocean turbulent mixing, followed by episodic nutrient supply to the euphotic zone and phytoplankton blooms. However, it is unclear whether such responses to strong winds occur in the ice‐free Canada Basin, where the seasonal pycnocline is strong and the nutricline is deep. In the present study, we monitored a fixed‐point observation (FPO) station in the Canada Basin for about 3 weeks in the fall of 2014 to examine the oceanic and biological responses to strong winds. At the FPO site, oceanic microstructure measurements, hydrographic surveys, and water sampling were performed with high temporal resolution, recording internal wave propagation, eddy passage, and water mass changes. Strong winds and internal wave propagation significantly enhanced the mixing above and at the seasonal pycnocline, but their effects were diminished at the nutricline, which was much deeper than the seasonal pycnocline. Therefore, wind‐induced mixing did not increase the upward nutrient supply from the nutricline and did not impact phytoplankton (chlorophyll a ) distribution in the surface layer of the FPO site. The temporal evolution of the chlorophyll a concentration was most closely related to water mass changes. We also observed prominent subsurface chlorophyll a maxima with abundant large‐sized phytoplankton that were likely carried by warm‐core eddies to the FPO site. Phytoplankton biomass may have been sustained by the high concentration of ammonium within the eddy and ammonium regeneration at the seasonal pycnocline, where particulate organic matter likely accumulated.