Abstract
The general features of the Great Whirl (GW) off the Somali Coast in 2017 and its influences on chlorophyll a (Chl a) concentration were studied by using satellite data and model outputs. Results show that GW, which initiated at 7°N, 53°E on June 13, had a lifetime of 153 d with an average amplitude of 16 cm and an average radius of 205 km. After the formation of GW, the concentration of Chl a in the interior of GW showed a downward trend throughout its life cycle, except in early July and mid-October. In early July, the Chl a blooms in the interior of GW were attributed to the combined effect of three processes. They are eddy horizontal transportation, the deepening of the mixed layer caused by the monsoon and eddy pumping, and the upward transportation of nutrients caused by eddy-induced Ekman pumping. In October, the Chl a blooms were probably due to the weakening of GW. During the period, water exchange occurred more frequently across the eddy, thus phytoplanktons were imported into the interior of GW.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Atlas R, Hoffman R N, Ardizzone J, et al. 2011. A Cross-Calibrated, Multiplatform ocean surface wind velocity product for meteorological and oceanographic applications. Bulletin of the American Meteorological Society, 92(2): 157–174, doi: https://doi.org/10.1175/2010BAMS2946.1
Beal L M, Donohue K A. 2013. The Great Whirl: Observations of its seasonal development and interannual variability. Journal of Geophysical Research: Oceans, 118(1): 1–13, doi: https://doi.org/10.1029/2012JC008198
Brock J C, McClain C R, Luther M E, et al. 1991. The phytoplankton bloom in the northwestern Arabian Sea during the southwest monsoon of 1979. Journal of Geophysical Research: Oceans, 96(C1): 20623–20642
Chelton D B, Schlax M G, Samelson R M. 2011. Global observations of nonlinear mesoscale eddies. Progress in Oceanography, 91(2): 167–216, doi: https://doi.org/10.1016/j.pocean.2011.01.002
D’Ovidio F, De Monte S, Penna A D, et al. 2013. Ecological implications of eddy retention in the open ocean: a Lagrangian approach. Journal of Physics A Mathematical and Theoretical, 46(25): 254023, doi: https://doi.org/10.1088/1751-8113/46/25/254023
Falkowski P G, Ziemann D, Kolber Z, et al. 1991. Role of eddy pumping in enhancing primary production in the ocean. Nature, 352(6330): 55–58, doi: https://doi.org/10.1038/352055a0
Fischer J, Schott F A, Stramma L. 1996. Currents and transports of the Great Whirl-Socotra Gyre system during the summer monsoon, August 1993. Journal of Geophysical Research: Oceans, 101(C2): 3573–3587, doi: https://doi.org/10.1029/95JC03617
Garçon V C, Oschlies A, Doney S C, et al. 2001. The role of mesoscale variability on plankton dynamics in the North Atlantic. Deep-Sea Research Part II:Topical Studies in Oceanography, 48(10): 2199–2226, doi: https://doi.org/10.1016/S0967-0645(00)00183-1
Gaube P, Mcgillicuddy D J Jr, Chelton D B, et al. 2014. Regional variations in the influence of mesoscale eddies on near-surface chlorophyll. Journal of Geophysical Research: Oceans, 119(12): 8195–8220, doi: https://doi.org/10.1002/2014JC010111
Halpern D. 2002. Offshore Ekman transport and Ekman pumping off Peru during the 1997–1998 El Niño. Geophysical Research Letters, 29(5): 1075
Jensen T G. 1991. Modeling the seasonal undercurrents in the Somali Current system. Journal of Geophysical Research: Oceans, 96(C12): 22151–22167, doi: https://doi.org/10.1029/91JC02383
Kara B A, Rochford P A, Hurlburt H E. 2003. Mixed layer depth variability over the global ocean. Journal of Geophysical Research: Oceans, 108(C3): 3079, doi: https://doi.org/10.1029/2000JC000736
Kawamiya M. 2001. Mechanism of offshore nutrient supply in the western Arabian Sea. Journal of Marine Research, 59(5): 675–696, doi: https://doi.org/10.1357/002224001762674890
Lévy M, Shankar D, André J M, et al. 2007. Basin-wide seasonal evolution of the Indian Ocean’s phytoplankton blooms. Journal of Geophysical Research: Oceans, 112(C12): C12014, doi: https://doi.org/10.1029/2007JC004090
Lee C M, Jones B H, Brink K H, et al. 2000. The upper-ocean response to monsoonal forcing in the Arabian Sea: seasonal and spatial variability. Deep-Sea Research Part II: Topical Studies in Oceanography, 47(7–8): 1177–1226
Letelier R M, Karl D M, Abbott M R, et al. 2000. Role of late winter mesoscale events in the biogeochemical variability of the upper water column of the North Pacific Subtropical Gyre. Journal of Geophysical Research: Oceans, 105(C12): 28723–28739, doi: https://doi.org/10.1029/1999JC000306
Liao Xiaomei, Du Yan, Zhan Haigang, et al. 2014. Summertime phytoplankton blooms and surface cooling in the western south equatorial Indian Ocean. Journal of Geophysical Research: Oceans, 119(11): 7687–7704, doi: https://doi.org/10.1002/2014JC010195
Liao Xiaomei, Zhan Haigang, Du Yan. 2016. Potential new production in two upwelling regions of the western Arabian Sea: Estimation and comparison. Journal of Geophysical Research: Oceans, 121(7): 4487–4502, doi: https://doi.org/10.1002/2016JC011707
Madec G. 2008. NEMO Ocean Engine. Paris: France: Institut PierreSimon Laplace (IPSL), 1288–1619
Madec G, Imbard M. 1996. A global ocean mesh to overcome the North Pole singularity. Climate Dynamics, 12(6): 381–388, doi: https://doi.org/10.1007/BF00211684
Mahadevan A. 2014. Ocean Science: eddy effects on biogeochemistry. Nature, 506(7487): 168–169, doi: https://doi.org/10.1038/nature13048
McCreary J P, Kundu P K. 1988. A numerical investigation of the somali current during the southwest monsoon. Journal of Marine Research, 46(1): 25–58, doi: https://doi.org/10.1357/002224088785113711
McCreary J P, Murtugudde R, Vialard J, et al. 2009. Biophysical processes in the indian ocean. In: Wiggert J D, ed. Indian Ocean Biogeochemical Processes and Ecological Variability. Washington, DC: American Geophysical Union
McGillicuddy D J Jr. 2016. Mechanisms of physical-biological-biogeo-chemical interaction at the oceanic mesoscale. Annual Review of Marine Science, 8: 125–159, doi: https://doi.org/10.1146/annurev-marine-010814-015606
McGillicuddy D J Jr, Anderson L A, Doney S C, et al. 2003. Eddy-driven sources and sinks of nutrients in the upper ocean: results from a 0.1 resolution model of the North Atlantic. Global Biogeochemical Cycles, 17(2): 1035
McGillicuddy D J Jr, Robinson A R, Siegel D A, et al. 1998. Influence of mesoscale eddies on new production in the Sargasso Sea. Nature, 394(6690): 263–266, doi: https://doi.org/10.1038/28367
Melzer B A, Jensen T G, Rydbeck A V. 2019. Evolution of the great whirl using an Altimetry-Based eddy tracking algorithm. Geophysical Research Letters, 46(8): 4378–4385, doi: https://doi.org/10.1029/2018GL081781
Oschlies A, Garçon V. 1998. Eddy-induced enhancement of primary production in a model of the North Atlantic Ocean. Nature, 394(6690): 266–269, doi: https://doi.org/10.1038/28373
Pujol M I, Faugère Y, Taburet G, et al. 2016. DUACS DT2014: the new multi-mission altimeter data set reprocessed over 20 years. Ocean Science, 12(5): 1067–1090, doi: https://doi.org/10.5194/os-12-1067-2016
Renault L, Dewitte B, Marchesiello P, et al. 2012. Upwelling response to atmospheric coastal jets off central Chile: A modeling study of the October 2000 event. Journal of Geophysical Research: Oceans, 117(C2): C02030
Risien C M, Chelton D B. 2008. A global climatology of surface wind and wind stress fields from eight years of QuikSCAT scatterometer data. Journal of Physical Oceanography, 38(11): 2379–2413, doi: https://doi.org/10.1175/2008JPO3881.1
Schott F A, Jürgen F, Garternicht U, et al. 1997. Summer monsoon response of the Northern Somali Current, 1995. Geophysical Research Letters, 24(21): 2565–2568, doi: https://doi.org/10.1029/97GL00888
Schott F A, McCreary J P Jr. 2001. The monsoon circulation of the Indian Ocean. Progress in Oceanography, 51(1): 1–123, doi: https://doi.org/10.1016/S0079-6611(01)00083-0
Siegel D A, McGillicuddy D J Jr, Fields E A. 1999. Mesoscale eddies, satellite altimetry, and new production in the Sargasso Sea. Journal of Geophysical Research: Oceans, 104(C6): 13359–13379, doi: https://doi.org/10.1029/1999JC900051
Siegel D A, Peterson P, McGillicuddy D J Jr, et al. 2011. Bio-optical footprints created by mesoscale eddies in the Sargasso Sea. Geophysical Research Letters, 38(13): L13608
Schott F A, Xie Shangping, McCreary J P Jr. 2009. Indian Ocean circulation and climate variability. Reviews of Geophysics, 47(1): RG1002
Wiggert J D, Hood R R, Banse K, et al. 2005. Monsoon-driven biogeochemical processes in the Arabian Sea. Progress in Oceanography, 65(2–4): 176–213
Wirth A, Willebrand J, Schott F A. 2002. Variability of the Great Whirl from observations and models. Deep-Sea Research Part II: Topical Studies in Oceanography, 49(7–8): 1279–1295
Young D K, Kindle J C. 1994. Physical processes affecting availability of dissolved silicate for diatom production in the Arabian Sea. Journal of Geophysical Research: Oceans, 99(C11): 22619–22632, doi: https://doi.org/10.1029/94JC01449
Acknowledgements
We thank the Big Earth Data Repository for the sea surface chlorophyll a concentration data (http://repository.casearth.cn/), AVISO database for the SSH anomaly and Mesoscale Eddy Trajectory Atlas (https://www.aviso.altimetry.fr/en/home.html), CCMP for the ocean vector wind (https://climatedataguide.ucar.edu/climate-data/ccmp-cross-calibrated-multi-platform-wind-vector-analysis), and CMEMS for the analysis and forecast product (https://resources.marine.copernicus.eu/).
Author information
Authors and Affiliations
Corresponding author
Additional information
Foundation item: The National Natural Science Foundation of China under contract Nos 41830538 and 42090042; the Chinese Academy of Sciences Fund under contract Nos XDA15020901, 133244KYSB20190031, ZDRW-XH-2019-2, ISEE2021PY02 and ISEE2021ZD01; Guangdong Basic and Applied Basic Research Fund under contract No. 2020A1515010498; the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) Fund under contract Nos GML2019ZD0303 and 2019BT02H594.
Rights and permissions
About this article
Cite this article
Dai, L., Han, B., Tang, S. et al. Influences of the Great Whirl on surface chlorophyll a concentration off the Somali Coast in 2017. Acta Oceanol. Sin. 40, 79–86 (2021). https://doi.org/10.1007/s13131-021-1740-3
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s13131-021-1740-3