Spatiotemporal Variability of Remote Sensing Ocean Net Primary Production and Major Forcing Factors in the Tropical Eastern Indian and Western Pacific Ocean

Kunsheng Xiang,Yanyan Li,Jingyi Liu,Qing Dong,Fanping Kong,Zi Yin

doi:10.3390/rs11040391

Abstract

Based on widely used remote sensing ocean net primary production (NPP) datasets, the spatiotemporal variability of NPP is first analyzed over the tropical eastern Indian and western Pacific Ocean for the period 1998–2016 using the conventional empirical orthogonal function (EOF), the lead–lag correlation and the ensemble empirical mode decomposition (EEMD) technique. Barnett and Preisendorfer’s improved Canonical Correlation Analysis (BPCCA) is also applied to derive covariability patterns of NPP with major forcing factors of the chlorophyll a concentration (Chla), sea surface temperature (SST), sea level anomaly (SLA), ocean rainfall (Rain), sea surface wind (Wind), and current (CUR) under climate changes of El Niño–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). We find that: (1) The first two seasonal EOF modes capture significant temporal and meridional NPP variability differences, as NPP reaches peaks approximately three months later in the western Pacific Ocean than that of in the eastern Indian Ocean. (2) The second and third interannual EOF modes are closely related with ENSO with a two-month lag and synchronous with IOD, respectively, characterized by southwesterly positive anomaly centers during positive IOD years. (3) NPP presents different varying tendencies and similar multiscale oscillation patterns with interannual and interdecadal cycles of 2~3 years, 5~8 years, and 9~19 years in subregions of the Bay of Bengal, the South China Sea, the southeastern Indian Ocean, and the northwestern Pacific Ocean. (4) The NPP variability is strongly coupled with negative SST, SLA, and Rain anomalies, as well as positive Chla, Wind and CUR anomalies in general during El Niño/positive IOD years. The results reveal the diversity and complexity of large-scale biophysical interactions in the key Indo-Pacific Warm Pool region, which improves our understanding of ocean productivity, ecosystems, and carbon budgets.

Highlights

Contributing roughly half of the biosphere’s net primary production (NPP), photosynthesis by oceanic phytoplankton is a vital link in the cycling of carbon between living and inorganic stocks, whose variability profoundly affects the global carbon cycle and climate changes [1,2]
We use Chla datasets from the Ocean Color Climate Change Initiative (OC-CCI); sea surface temperature (SST) datasets from the NOAA High Resolution SST data provided by the NOAA/OAR/ESRL PSD; sea level anomaly (SLA) datasets from the Archiving, Validation and Interpretation of Satellite Oceanographic (AVISO); rain datasets from the Tropical Rainfall Measuring Mission (TRMM) 3B43 precipitation product, provided by the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC); wind datasets from the Cross-Calibrated Multi-Platform (CCMP) Version-2.0 vector wind analyses produced by Remote Sensing Systems; and ocean current (CUR) datasets from the GLOBAL-REANALYSIS-PHY-001-030 reanalysis product provided by the Copernicus Marine Environment Monitoring Service (CMEMS)
To investigate the dominant mechanisms driving the diverse biophysical interactions associated with El Niño–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD), we find that the combined effects of the deepening thermocline, weak vertical mixing, formative downwelling, reduced river discharge and solar radiation process could explain why NPP decreases in the southern South China Sea (SCS) and western Bay of Bengal (BoB) as well as the equatorial Pacific east of 155◦E and the central southern Indian Ocean during El Niño years

Summary

Introduction

Contributing roughly half of the biosphere’s net primary production (NPP), photosynthesis by oceanic phytoplankton is a vital link in the cycling of carbon between living and inorganic stocks, whose variability profoundly affects the global carbon cycle and climate changes [1,2]. Its remote forcing on biological variation in the tropical eastern Indian Ocean has received far less attention, with the exception of Currie et al [7], who studied the Chla anomaly patterns for the period 1961–2001 driven by ENSO and IOD within the Indian Ocean using a coupled model. The ocean primary production has been found to be low in the western Pacific but with strong biological variability associated with ENSO [15,16,17,18,19]. Though the spatiotemporal variability of Chla associated with the physical variables of sea surface temperature (SST), sea level anomaly (SLA), sea surface wind (Wind) and ENSO have been studied in western Pacific on seasonal and interannual timescale by Hou et al [17], the possible influence of IOD events was not included

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Results

Conclusion