Japan Geoscience Union Meeting 2019

Presentation information

[J] Oral

A (Atmospheric and Hydrospheric Sciences ) » A-OS Ocean Sciences & Ocean Environment

[A-OS16] Chemical and Biological Oceanography

Mon. May 27, 2019 3:30 PM - 5:00 PM 303 (3F)

convener:Namiha Yamada(National Institute of Advanced Industrial Science and Technology), Sayaka Yasunaka(Japan Agency for Marine-Earth Science and Technology), Hiroaki Saito(Atmosphere and Ocean Research Institute, The University of Tokyo), Chairperson:Tsuneo Ono(Japan Fisheries Research and Education Agency), Naohiro Kosugi(気象研究所)

4:15 PM - 4:30 PM

[AOS16-04] Reconstruction of spatiotemporal change of anthropogenic fixed nitrogen in the western North Pacific

*Yutaka Watanabe1, Kouichi Fujita1, BOFENG LI1 (1.Hokkaido University)

Keywords:anthropogenic fixed nitrogen, western North Pacific, parameterization

We constructed parameterizations for the estimation of ocean fixed nitrogen (N) in the western North Pacific. Parameterizations (Np), determined as a function of temperature (T), potential density (sigma-theta) and dissolved oxygen (DO), provided strong correlations with direct measurements for ocean nitrogen (Np = – 2.24T – 4.70sigma-theta – 0.0970DO + 182.2; the coefficient of determination (r2) = 0.988; the root mean square error (RMSE) = 1.25 umol kg-1). Predicted N values were consistent with previous independent hydrographic observations, generally within the above error. By applying T, sigma-theta and DO time-series data from ship observations to our parameterization, large seasonal variations in N were demonstrated in detail. Using the parameterization technique along with the time series of observed N (Nobs) found the significant increasing rate of oceanic anthropogenic fixed nitrogen (Nanth) in the past four decades in the western North Pacific subtropical region.