The Taiwan-JGOFS Report

1994

JGOFS Committee located in Taipei, Taiwan

The Republic of China

________________________________________________

October 1994

Table of contents

Contribution of This Report

Preface

Summary

INTRODUCTION

The organization

Goals of the study

Study area

RECENT RESULTS AND FUTURE STUDY

Water circulation

Hydrography

Primary production and phytoplankton

Trophic dynamics and fisheries

Euphotic zone particle dynamics

Deep sea particle flux and sedimentation

Benthic biogeochemistry

Air/sea gas exchange

Modeling

Data management

INTERNATIONAL COOPERATION

REFERENCES

APPENDIX A: KEEP PUBLICATIONS

APPENDIX B: LIST OF SCIENTISTS & EXPERTISE

APPENDIX C: LIST OF ACRONYMS

JGOFS Committee located in Taipei, Taiwan

The Republic of China

Jeng Chang

Ju-Chin Chen

Tai-Sheng Chiu

Yu-Chia Chung

Saulwood Lin

Kon-Kee Liu (Chairman)

Tswen Yung Tang

Ching-Ling Wei

Contact person:

Kon-Kee Liu

Institute of Oceanography, National Taiwan University

Taipei, Taiwan, ROC

Fax: 886-2-362-6092 Internet: kkliu@ccms.ntu.edu.tw

Contributors of this report

Tai-Sheng Chiu

Saulwood Lin

Kon-Kee Liu (Editor)

Tswen Yung Tang

Ching-Ling Wei

Chen-Tung Arthur Chen

Yu-Chia Chung

Jia-Jong Hung

Jeng Chang

Gwo-Ching Gong

Preface

The Kuroshio Edge Exchange Processes (KEEP) program, which forms the backbone of the Taiwan JGOFS program, enters its second phase in August this year. The new program is entitled the Kuroshio-East China Sea Shelf Exchange Processes (KEEP-II) study. The scientific rationale for participating in the JGOFS program has been developed by community-wide interactive planning and a joint Taiwan-USA Workshop on Frontal Exchange Processes held at Stony Brook in May 1988. The Workshop, sponsored by the National Science Council (NSC) of China (Taipei) and the National Science Foundation of USA, was organized by Drs. Dong-Ping Wang and Wen-Ssn Chuang of SUNY and NTU, respectively.

The workshop generated a great deal of intellectual excitement and strongly endorsed the Kuroshio Edge Exchange Processes (KEEP) program, which forms the backbone of the Taiwan JGOFS program. Among the American participants, many were involved in the SEEP programs, and lent their wisdom to KEEP. Shortly after the workshop, the program was initiated in 1989 with the support of NSC. The motivation for such program arose out of a common concern for the implication of future climate change and a need of better knowledge regarding the material exchange between the Kuroshio and the East China Sea waters and its consequences

At the JGOFS-7 Scientific Steering Committee Meeting in Taipei in October 1992, a JGOFS/LOICZ joint task team was formed to implement the continental margins study, which is expected to provide the boundary conditions for the biogeochemical cycle of carbon in the oceans. KEEP and KEEP-II are the manifestation of such an attempt to explore the boundary fluxes. The KEEP and KEEP-II programs have been developed continually in the past five years through firm support of NSC and enthusiastic participation of more than 120 scientists, technicians and students. The sustained interests in these scientific issues reflect the commitment to the Global Change research of the scientific community of Taiwan.

This report is the result of a cooperative effort by the JGOFS Committee located in Taipei, China under the national IGBP Committee, and the KEEP-II Program under the National Science Council. It is our hope that this document will not only serve as a status report but will also stimulate discussion which may help us in building a world-class contribution to the understanding of the role of the Oceans in determining the future climate of the Earth.

Summary

Taiwan is situated in a unique position to study the interaction between the two largest ecosystems in the world, namely, the terrestrial system of the Asian continent and the oceanic system of the Pacific. The major contribution from Taiwan to the international JGOFS program is the Kuroshio-East China Sea Shelf Exchange Processes (KEEP-II) study. This project is the sequel to the Kuroshio Edge Exchange Processes (KEEP) study. This report provides background information of the East China Sea and recent results from the KEEP program and presents future research plan for the KEEP-II program. KEEP (1989-1994) was originally developed out of the interest of Taiwanese oceanographers in the water exchange across the Kuroshio frontal zone in the East China Sea northeast of Taiwan and the concomitant biogeochemical fluxes. As the significance of carbon fluxes at the continental margins is increasingly recognized, KEEP was later included in the JGOFS implementation plan.

In the past five years, many important discoveries were made in the KEEP program. The Kuroshio encounters the continental shelf northeast of Taiwan and turns to the northeast partially. Part of the Kuroshio surface water spills over the shelf and some subsurface water forms a counter current hugging to the upper slope and upwells to the shelf along submarine canyons. A series of hydrographic survey showed a permanent upwelling center at the shelf break to the north of Taiwan. High primary productivity (up to 1.5 gC/m2/d) was observed in region of strong upwelling. In comparison, the mean primary productivity in the East China Sea is estimated in the range of 0.15-0.9 gC/m2/d.

Upwelling actually occurs at the shelf break along the path of the Kuroshio in the Okinawa Trough but the intensity is variable. In addition to the upwelling center northeast of Taiwan, stronger upwelling also occurs at the shelf break east of the Changjiang river mouth. The upwelled water is an important source of nutrients for the middle and outer shelf of the East China Sea and especially in the southern part north of Taiwan. The Changjiang (Yangtze River) runoff is another important nutrient source which has strong influence over the Changjiang Diluted Water and the China Coastal Water.

The particle residence time in the southern East china Sea based on 234Th measurement is 1-3 days for the coastal water, 3-5 days for the shelf water, and 10-40 days for the water off the shelf. The biogenic material produced on the shelf is actively transported to the deep water by tidal motion as indicated by high sediment fluxes collected in traps deployed on the slope. Preferential deposition of organic matter was found on the mid-slope. Mid-depth maxima of particulate matter, including organic carbon, above the slope off the shelf break witness the lateral transport. Extremely high flux of Pb-210 (up to 2000 dpm/m2/d) and high sedimentation rate (up to 0.5 cm/yr) was measured on the slope in the same region where exists a depocenter of organic carbon (0.8 %). Active sulfate reduction occurs in the organic carbon-rich sediments. These discoveries indicate very active biogeochemical processes induced by the interaction between the Kuroshio and the shelf water of the East China Sea. The continental slope and the Okinawa Trough appear to be an effective sink for the particulate matter in the East China Sea shelf.

We will continue the investigation in KEEP-II, which is planned for 1994-1999, with enlarged study area covering the East China Sea and the Taiwan Strait. The new program will focus on two types of processes: those which control the primary and new production in the East China Sea, and those that affect the lateral transport of particulate matter to the deep sea. Sediment traps for the euphotic zone will be deployed in the shelf water in order to determine the particle fluxes at the bottom of the euphotic zone in the high productivity area. The pelagic sediment traps will be deployed in the Okinawa Trough to measure the sediment flux and to characterize the materials deposited in the trough. Sedimentation rates and sedimentary oxidation rates will be determined. In order to cover the large study area, satellite remote sensing, such as the SeaWiFS imagery, is expected to play an critical role in KEEP-II. The trophic dynamics of the pelagic food web will be studied for a better management of the fishing activities in the East China Sea.

International collaboration is an important element in the Taiwan JGOFS program. The data from the our studies will be available to the international JGOFS community. We appreciate comments and suggestions that improve our program, and welcome proposals for future collaboration.