Evaluation of Ocean Biogeochemistry Simulation within NEMO-TOPAZ, a Newly Developed Ocean Biogeochemistry Model

Hyojin Park1, Hyomee Lee2, Byung-Kwon Moon3, Hyun-Chae Jung4, Jong-Yeon Park3, Jieun Wie5, Young-Hwa Byun6, Yoon-Jin Lim7 and Johan Lee8, (1)Organization Not Listed, Washington, DC, United States, (2)National Institute of Meteorological Sciences, Global Environment System Research Division, Seogwipo, Korea, Republic of (South), (3)Chonbuk National University, Jeonju, South Korea, (4)Mirae Climate, South Korea, (5)Chonbuk National University, South Korea, (6)National Institute of Meteorological Sciences, Seogwipo-si, South Korea, (7)National Institute of Meteorological Sciences, Climate Research Division, Seogwipo, South Korea, (8)National Institute of Meteorological Sciences, Seogwipo, South Korea
The ocean biogeochemistry process affects the climate system through interaction with the atmosphere, and recent developments in the earth system model reflect this process with the ocean biogeochemistry model. We developed a new biogeochemistry model NEMO-TOPAZ by incorporating biogeochemistry module Tracers of Ocean Phytoplankton with Allometric Zooplankton (TOPAZ) with Nucleus for European Modelling of the Ocean (NEMO). Biogeochemistry simulation of NEMO-TOPAZ was assessed through this research, and the results will be the basis for improving its performance. Other biogeochemistry models, NEMO-PISCES and three models of CMIP6 OMIP, were compared for their performance. The COREv2 atmosphere forcing is prescribed and analysis period was from 1981 to 2009. The variables used for evaluation were chlorophyll, an ocean biogeochemistry variable, as well as nitrate, phosphate, silicate, dissolved oxygen (DO), alkalinity, and dissolved inorganic carbon (DIC). In addition, other basic physical variables including temperature and salinity were also evaluated. SeaWiFS for chlorophyll, GLODAPv2 for alkalinity and DIC, and WOA2018 for the other variables were utilized as observation data.

As a result of the analysis, NEMO-TOPAZ has over-simulated the concentration of surface chlorophyll in the seas where the chlorophyll concentration (Tropical Pacific Ocean, high-latitude Northern hemispheric seas, and the Antarctic) is higher than other seas. Though compared models over-estimated in these regions as well, the difference of error was larger for NEMO-TOPAZ. Although chlorophyll errors in NEMO-TOPAZ were related to overly prescribe iron deposition from the atmosphere. When the smaller values of iron deposition from NEMO-PISCES was diagnosed instead, chlorophyll concentration was reduced As a result of RMSE of surface biogeochemistry variables, alkalinity and DIC comparatively showed good reproduction performance in NEMO-TOPAZ, but nitrate, phosphate, silicate, and DO were simulated with lesser quality than the others. Surface biogeochemistry variable errors from analyzed models were distinctly displayed in the Antarctic Ocean which displayed more fluctuations than other seas. NEMO-TOPAZ represented well the vertical structures of biogeochemical variables in the Pacific and the Atlantic Ocean than NEMO-PISCES.

This work was funded by the Korea Meteorological Administration Research and Development Program under Grant KMI (KMI2018-03513). The main calculations were performed by using the supercomputing resource of the Korea Meteorological Administration (National Center for Meteorological Supercomputer)