Comparison of ADCP and ECCOv4r4 Currents in the Pacific Equatorial Undercurrent

Author:

Halpern David1,Le Megan K.23,Smith Timothy A.456,Heimbach Patrick478

Affiliation:

1. a Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California

2. b Department of Computer Science, The University of Texas at Austin, Austin, Texas

3. c Department of Mathematics, The University of Texas at Austin, Austin, Texas

4. d Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, Texas

5. e Cooperative Institute for Research in Environmental Sciences, Boulder, Colorado

6. f Physical Sciences Laboratory, National Oceanic and Atmospheric Administration, Boulder, Colorado

7. g Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas

8. h Institute for Geophysics, The University of Texas at Austin, Austin, Texas

Abstract

Abstract The Pacific Equatorial Undercurrent (EUC) flows eastward across the Pacific at the equator in the thermocline. Its variability is related to El Niño. Moored acoustic Doppler current profiler (ADCP) measurements recorded at four widely separated sites along the equator in the EUC were compared to currents generated by version 4 release 4 of the Estimating the Circulation and Climate of the Ocean (ECCOv4r4) global model–data synthesis product. We are interested to learn how well ECCOv4r4 currents could complement sparse in situ current measurements. ADCP measurements were not assimilated in ECCOv4r4. Comparisons occurred at 5-m depth intervals at 165°E, 170°W, 140°W, and 110°W over time intervals of 10–14 years from 1995 to 2010. Hourly values of ECCOv4r4 and ADCP EUC core speeds were strongly correlated, similar for the EUC transport per unit width (TPUW). Correlations were substantially weaker at 110°W. Although we expected means and standard deviations of ECCOv4r4 currents to be smaller than ADCP values because of ECCOv4r4’s grid representation error, the large differences were unforeseen. The appearance of ECCOv4r4 diurnal-period current oscillations was surprising. As the EUC moved eastward from 170° to 140°W, the ECCOv4r4 TPUW exhibited a much smaller increase compared to the ADCP TPUW. A consequence of smaller ECCOv4r4 EUC core speeds was significantly fewer instances of gradient Richardson number (Ri) less than 1/4 above and below the depth of the core speed compared to Ri computed with ADCP observations. We present linear regression analyses to use monthly-mean ECCOv4r4 EUC core speeds and TPUWs as proxies for ADCP measurements. Significance Statement Hundreds of scientific papers have used ECCO data products generated with a continually evolving state-of-the-art ocean-model–data synthesis system. We ask, How representative is the latest version of ECCO equatorial ocean currents? We use independent in situ current measurements as the reference dataset to establish the accuracy of ECCO currents in the tropical Pacific. Attention is focused on the Pacific Equatorial Undercurrent (EUC) because it contributes to the formation of El Niño and La Niña events. ECCO EUC core speeds were smaller in magnitude and less variable in time compared to observations. As a consequence, ECCO currents generated smaller vertical mixing in the EUC compared to that inferred from current measurements. We developed a linear regression model to improve representation of monthly-mean ECCO currents.

Funder

Climate Program Office

Publisher

American Meteorological Society

Subject

Atmospheric Science,Ocean Engineering

Reference47 articles.

1. Atmospheric teleconnections from the equatorial Pacific;Bjerknes, J.,1969

2. Persistent effect of El Niño on global economic growth;Callahan, C. W.,2023

3. Le courant de Cromwell dans le Pacifique central en février;Colin, C.,1971

4. Equatorial Undercurrent in the Pacific revealed by new methods;Cromwell, T.,1954

5. ECCO Consortium, I. Fukumori, O. Wang, I. Fenty, G. Forget, P. Heimbach, and R. M. Ponte, 2021: Synopsis of the ECCO Central Production global ocean and sea-ice state estimate (version 4 release 4). Zenodo, https://doi.org/10.5281/zenodo.4533349.

同舟云学术

1.学者识别学者识别

2.学术分析学术分析

3.人才评估人才评估

"同舟云学术"是以全球学者为主线,采集、加工和组织学术论文而形成的新型学术文献查询和分析系统,可以对全球学者进行文献检索和人才价值评估。用户可以通过关注某些学科领域的顶尖人物而持续追踪该领域的学科进展和研究前沿。经过近期的数据扩容,当前同舟云学术共收录了国内外主流学术期刊6万余种,收集的期刊论文及会议论文总量共计约1.5亿篇,并以每天添加12000余篇中外论文的速度递增。我们也可以为用户提供个性化、定制化的学者数据。欢迎来电咨询!咨询电话:010-8811{复制后删除}0370

www.globalauthorid.com

TOP

Copyright © 2019-2024 北京同舟云网络信息技术有限公司
京公网安备11010802033243号  京ICP备18003416号-3