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ArticleInterannual variability of the surface summertime eastward jet in the South China Sea(John Wiley & Sons, 2014-10-27) Li, Yuanlong ; Han, Weiqing ; Wilkin, John L. ; Zhang, Weifeng G. ; Arango, Hernan G. ; Zavala-Garay, Javier ; Levin, Julia C. ; Castruccio, Frederic S.The summertime eastward jet (SEJ) located around 12°N, 110°E–113°E, as the offshore extension of the Vietnam coastal current, is an important feature of the South China Sea (SCS) surface circulation in boreal summer. Analysis of satellite-derived sea level and sea surface wind data during 1992–2012 reveals pronounced interannual variations in its surface strength (SSEJ) and latitudinal position (YSEJ). In most of these years, the JAS (July, August, and September)-mean SSEJ fluctuates between 0.17 and 0.55 m s−1, while YSEJ shifts between 10.7°N and 14.3°N. These variations of the SEJ are predominantly contributed from the geostrophic current component that is linked to a meridional dipole pattern of sea level variations. This sea level dipole pattern is primarily induced by local wind changes within the SCS associated with the El Niño-Southern Oscillation (ENSO). Enhanced (weakened) southwest monsoon at the developing (decaying) stage of an El Niño event causes a stronger (weaker) SEJ located south (north) of its mean position. Remote wind forcing from the tropical Pacific can also affect the sea level in the SCS via energy transmission through the Philippine archipelago, but its effect on the SEJ is small. The impact of the oceanic internal variability, such as eddy-current interaction, is assessed using an ocean general circulation model (OGCM). Such impact can lead to considerable year-to-year changes of sea level and the SEJ, equivalent to ∼20% of the observed variation. This implies the complexity and prediction difficulty of the upper ocean circulation in this region.
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ArticleA road map to IndOOS-2 better observations of the rapidly warming Indian Ocean(American Meteorological Society, 2020-11-01) Beal, Lisa M. ; Vialard, Jérôme ; Roxy, Mathew Koll ; Li, Jing ; Andres, Magdalena ; Annamalai, Hariharasubramanian ; Feng, Ming ; Han, Weiqing ; Hood, Raleigh R. ; Lee, Tong ; Lengaigne, Matthieu ; Lumpkin, Rick ; Masumoto, Yukio ; McPhaden, Michael J. ; Ravichandran, M. ; Shinoda, Toshiaki ; Sloyan, Bernadette M. ; Strutton, Peter G. ; Subramanian, Aneesh C. ; Tozuka, Tomoki ; Ummenhofer, Caroline C. ; Unnikrishnan, Shankaran Alakkat ; Wiggert, Jerry D. ; Yu, Lisan ; Cheng, Lijing ; Desbruyères, Damien G. ; Parvathi, V.The Indian Ocean Observing System (IndOOS), established in 2006, is a multinational network of sustained oceanic measurements that underpin understanding and forecasting of weather and climate for the Indian Ocean region and beyond. Almost one-third of humanity lives around the Indian Ocean, many in countries dependent on fisheries and rain-fed agriculture that are vulnerable to climate variability and extremes. The Indian Ocean alone has absorbed a quarter of the global oceanic heat uptake over the last two decades and the fate of this heat and its impact on future change is unknown. Climate models project accelerating sea level rise, more frequent extremes in monsoon rainfall, and decreasing oceanic productivity. In view of these new scientific challenges, a 3-yr international review of the IndOOS by more than 60 scientific experts now highlights the need for an enhanced observing network that can better meet societal challenges, and provide more reliable forecasts. Here we present core findings from this review, including the need for 1) chemical, biological, and ecosystem measurements alongside physical parameters; 2) expansion into the western tropics to improve understanding of the monsoon circulation; 3) better-resolved upper ocean processes to improve understanding of air–sea coupling and yield better subseasonal to seasonal predictions; and 4) expansion into key coastal regions and the deep ocean to better constrain the basinwide energy budget. These goals will require new agreements and partnerships with and among Indian Ocean rim countries, creating opportunities for them to enhance their monitoring and forecasting capacity as part of IndOOS-2.
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ArticleTowards comprehensive observing and modeling systems for monitoring and predicting regional to coastal sea level(Frontiers Media, 2019-07-25) Ponte, Rui M. ; Carson, Mark ; Cirano, Mauro ; Domingues, Catia M. ; Jevrejeva, Svetlana ; Marcos, Marta ; Mitchum, Gary ; van de Wal, Roderik S.W. ; Woodworth, Philip L. ; Ablain, Michaël ; Ardhuin, Fabrice ; Ballu, Valerie ; Becker, Mélanie ; Benveniste, Jérôme ; Birol, Florence ; Bradshaw, Elizabeth ; Cazenave, Anny ; De Mey-Frémaux, Pierre ; Durand, Fabien ; Ezer, Tal ; Fu, Lee-Lueng ; Fukumori, Ichiro ; Gordon, Kathy ; Gravelle, Médéric ; Griffies, Stephen M. ; Han, Weiqing ; Hibbert, Angela ; Hughes, Chris W. ; Idier, Deborah ; Kourafalou, Vassiliki H. ; Little, Christopher M. ; Matthews, Andrew ; Melet, Angelique ; Merrifield, Mark ; Meyssignac, Benoit ; Minobe, Shoshiro ; Penduff, Thierry ; Picot, Nicolas ; Piecuch, Christopher G. ; Ray, Richard D. ; Rickards, Lesley ; Santamaría-Gómez, Alvaro ; Stammer, Detlef ; Staneva, Joanna ; Testut, Laurent ; Thompson, Keith ; Thompson, Philip ; Vignudelli, Stefano ; Williams, Joanne ; Williams, Simon D. P. ; Wöppelmann, Guy ; Zanna, Laure ; Zhang, XuebinA major challenge for managing impacts and implementing effective mitigation measures and adaptation strategies for coastal zones affected by future sea level (SL) rise is our limited capacity to predict SL change at the coast on relevant spatial and temporal scales. Predicting coastal SL requires the ability to monitor and simulate a multitude of physical processes affecting SL, from local effects of wind waves and river runoff to remote influences of the large-scale ocean circulation on the coast. Here we assess our current understanding of the causes of coastal SL variability on monthly to multi-decadal timescales, including geodetic, oceanographic and atmospheric aspects of the problem, and review available observing systems informing on coastal SL. We also review the ability of existing models and data assimilation systems to estimate coastal SL variations and of atmosphere-ocean global coupled models and related regional downscaling efforts to project future SL changes. We discuss (1) observational gaps and uncertainties, and priorities for the development of an optimal and integrated coastal SL observing system, (2) strategies for advancing model capabilities in forecasting short-term processes and projecting long-term changes affecting coastal SL, and (3) possible future developments of sea level services enabling better connection of scientists and user communities and facilitating assessment and decision making for adaptation to future coastal SL change.
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ArticleA sustained ocean observing system in the Indian Ocean for climate related scientific knowledge and societal needs(Frontiers Media, 2019-06-28) Hermes, Juliet ; Masumoto, Yukio ; Beal, Lisa M. ; Roxy, Mathew Koll ; Vialard, Jérôme ; Andres, Magdalena ; Annamalai, Hariharasubramanian ; Behera, Swadhin ; D’Adamo, Nick ; Doi, Takeshi ; Feng, Ming ; Han, Weiqing ; Hardman-Mountford, Nick ; Hendon, Harry ; Hood, Raleigh R. ; Kido, Shoichiro ; Lee, Craig M. ; Lee, Tong ; Lengaigne, Matthieu ; Li, Jing ; Lumpkin, Rick ; Navaneeth, K. N. ; Milligan, Ben ; McPhaden, Michael J. ; Ravichandran, M. ; Shinoda, Toshiaki ; Singh, Arvind ; Sloyan, Bernadette M. ; Strutton, Peter G. ; Subramanian, Aneesh C. ; Thurston, Sidney ; Tozuka, Tomoki ; Ummenhofer, Caroline C. ; Unnikrishnan, Shankaran Alakkat ; Venkatesan, Ramasamy ; Wang, Dongxiao ; Wiggert, Jerry D. ; Yu, Lisan ; Yu, WeidongThe Indian Ocean is warming faster than any of the global oceans and its climate is uniquely driven by the presence of a landmass at low latitudes, which causes monsoonal winds and reversing currents. The food, water, and energy security in the Indian Ocean rim countries and islands are intrinsically tied to its climate, with marine environmental goods and services, as well as trade within the basin, underpinning their economies. Hence, there are a range of societal needs for Indian Ocean observation arising from the influence of regional phenomena and climate change on, for instance, marine ecosystems, monsoon rains, and sea-level. The Indian Ocean Observing System (IndOOS), is a sustained observing system that monitors basin-scale ocean-atmosphere conditions, while providing flexibility in terms of emerging technologies and scientificand societal needs, and a framework for more regional and coastal monitoring. This paper reviews the societal and scientific motivations, current status, and future directions of IndOOS, while also discussing the need for enhanced coastal, shelf, and regional observations. The challenges of sustainability and implementation are also addressed, including capacity building, best practices, and integration of resources. The utility of IndOOS ultimately depends on the identification of, and engagement with, end-users and decision-makers and on the practical accessibility and transparency of data for a range of products and for decision-making processes. Therefore we highlight current progress, issues and challenges related to end user engagement with IndOOS, as well as the needs of the data assimilation and modeling communities. Knowledge of the status of the Indian Ocean climate and ecosystems and predictability of its future, depends on a wide range of socio-economic and environmental data, a significant part of which is provided by IndOOS.
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ArticleEquatorial waves substantially modulate currents in the tropical Indian Ocean(Cell Press, 2024-02-05) Chen, Gengxin ; Han, Weiqing ; Huang, Rui Xin ; Wang, DongxiaoThe Indian Ocean is a key component of the global thermohaline conveyor, linking global mass and heat exchanges, and has contributed to a quarter of the global oceanic heat uptake over the last two decades, fundamentally affecting weather and climate globally and regionally, especially its rim countries hosting one-third of the world’s population. To date, our knowledge of the complex Indian Ocean circulation that reverses with the monsoon is the poorest among the three ocean basins (Pacific, Atlantic, and Indian).