Intensification of upwelling along Oman coast in a warming scenario

Praveen, V.; Ajayamohan, R. S.; Valsala, Vinu; Sandeep, S.

doi:10.1002/2016gl069638

Cited by 41 publications

(32 citation statements)

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“…However, we are aware that future and past monsoon changes generally come in complex spatial and temporal patterns, which may affect the projected OMZ response. For instance, a recent study by Praveen et al (2016) suggests that summer monsoon intensification will affect more the northern Arabian Sea (i.e., Sea of Oman) than its southern part (i.e., the Somali coast). This could alter the response of the OMZ depending on how the overall Arabian Sea productivity changes.…”

Section: Limitations Of the Idealized Wind Change Scenariosmentioning

confidence: 99%

“…This high productivity in conjunction with a sluggish circulation sustains the world's thickest OMZ, responsible for up to 40 % of global pelagic denitrification despite occupying less than 2 % of the World Ocean area (Bange et al, 2005). Future climate projections suggest that Indian summer monsoon may intensify in the future under a warmer climate (e.g., Wang et al, 2013;Sandeep and Ajayamohan, 2015;Praveen et al, 2016;deCastro et al, 2016). Praveen et al (2016) found that the future upwelling intensification will affect essentially the coast of Oman.…”

Section: Introductionmentioning

confidence: 99%

“…Future climate projections suggest that Indian summer monsoon may intensify in the future under a warmer climate (e.g., Wang et al, 2013;Sandeep and Ajayamohan, 2015;Praveen et al, 2016;deCastro et al, 2016). Praveen et al (2016) found that the future upwelling intensification will affect essentially the coast of Oman. Using an ensemble of global and regional model simulations for the 21st century, deCastro et al (2016) show a strengthening of the Somali coastal upwelling that increases with latitude.…”

Section: Introductionmentioning

confidence: 99%

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Intensification and deepening of the Arabian Sea oxygen minimum zone in response to increase in Indian monsoon wind intensity

2018

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Abstract. The decline in oxygen supply to the ocean associated with global warming is expected to expand oxygen minimum zones (OMZs). This global trend can be attenuated or amplified by regional processes. In the Arabian Sea, the world's thickest OMZ is highly vulnerable to changes in the Indian monsoon wind. Evidence from paleorecords and future climate projections indicates strong variations of the Indian monsoon wind intensity over climatic timescales. Yet, the response of the OMZ to these wind changes remains poorly understood and its amplitude and timescale unexplored. Here, we investigate the impacts of perturbations in Indian monsoon wind intensity (from −50 to +50 %) on the size and intensity of the Arabian Sea OMZ, and examine the biogeochemical and ecological implications of these changes. To this end, we conducted a series of eddy-resolving simulations of the Arabian Sea using the Regional Ocean Modeling System (ROMS) coupled to a nitrogen-based nutrient-phytoplankton-zooplanktondetritus (NPZD) ecosystem model that includes a representation of the O 2 cycle. We show that the Arabian Sea productivity increases and its OMZ expands and deepens in response to monsoon wind intensification. These responses are dominated by the perturbation of the summer monsoon wind, whereas the changes in the winter monsoon wind play a secondary role. While the productivity responds quickly and nearly linearly to wind increase (i.e., on a timescale of years), the OMZ response is much slower (i.e., a timescale of decades). Our analysis reveals that the OMZ expansion at depth is driven by increased oxygen biological consumption, whereas its surface weakening is induced by increased ventilation. The enhanced ventilation favors episodic intrusions of oxic waters in the lower epipelagic zone (100-200 m) of the western and central Arabian Sea, leading to intermittent expansions of marine habitats and a more frequent alternation of hypoxic and oxic conditions there. The increased productivity and deepening of the OMZ also lead to a strong intensification of denitrification at depth, resulting in a substantial amplification of fixed nitrogen depletion in the Arabian Sea. We conclude that changes in the Indian monsoon can affect, on longer timescales, the large-scale biogeochemical cycles of nitrogen and carbon, with a positive feedback on climate change in the case of stronger winds. Additional potential changes in large-scale ocean ventilation and stratification may affect the sensitivity of the Arabian Sea OMZ to monsoon intensification.

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Section: Limitations Of the Idealized Wind Change Scenariosmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Intensification and deepening of the Arabian Sea oxygen minimum zone in response to increase in Indian monsoon wind intensity

2018

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“…The future fate of upwelling, in the context of global warming, is a subject of debate. Several studies have argued that there will be intensification of coastal upwelling in response to the amplified landsea pressure gradient in the warming world (Bakun 1990;deCastro et al 2016;Praveen et al 2016). However, the story in the monsoonal Indian Ocean may be far more complex.…”

Section: Upwelling Coastal-open Interactionsmentioning

confidence: 99%

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2020

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THIS EDITION of Exchanges focuses on the recent decadal review of the Indian Ocean Observing System (IndOOS) and its outcomes. IndOOS was established in 2006 under the visionary leadership of Dr. Gary Meyers (1941-2016), the founding chair of the CLIVAR/IOC-GOOS Indian Ocean Regional Panel (IORP), to address the need for a sustained observing system that consists of a variety of observing platforms to support weather and climate research and prediction. Key founding components of the IndOOS were a tropical basin-wide mooring array-the Research moored Array for African Asian Australian Monsoon Analysis and Prediction (RAMA)-and a network of repeat expendable bathythermograph (XBT) lines. Broad international participation and support, facilitated and coordinated by the regional GOOS alliance (IO-GOOS) and the IndOOS Resources Forum (IRF), have played a crucial role in maximizing the limited resources available to implement the IndOOS. IndOOS has now passed the 10-year milestone. A full decadal review report has recently been released as the outcome of a three-year review effort led by the IORP co-chairs, Lisa Beal, Jérôme Vialard, and Mathew Koll Roxy, with a writing team comprising more than 60 scientific experts. As highlighted in their article in this issue, the decadal review has generated 136 actionable recommendations and led to a roadmap of an enhanced observing system for the next decade (2020-2030). This second phase, IndOOS-2 (Figure 1, cover page), is designed to meet the current and future societal needs for seamless prediction of Indian Ocean climate and ecosystems across a wide range of timescales, from days to seasons to years to decades to centuries and beyond. Achieving goals of IndOOS-2 will depend critically on capacity building, resource management, regional partnerships, and information sharing. It is becoming more important than ever that the scientific community actively engages with stakeholders, policy makers, and civil society in the Indian Ocean rim countries to build and sustain IndOOS-2, and to address the grand challenges identified by the World Climate Research Program and the societal outcomes envisioned under the UN Decade of Ocean Science for Sustainable Development. The main body of this edition is a condensed version of the full IndOOS-2 report, reorganized under five main science themes: natural and anthropogenic warming of the Indian Ocean, monsoon and regional airsea interaction, ocean processes and modelling, physical and biogeochemical processes and interactions, and climate information and prediction across timescales. These themed articles, written by many lead authors of the full report, are meant to provide collective reviews that address the progress made and the gaps that still exist in understanding the complex dynamical and biogeochemical processes in the Indian Ocean, and in improving prediction skills for weather, climate, and ecosystems. The OceanObs'19 (16-21 September 2019, Hawaii) called for new cooperative models for Observing System Governance to better align...

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Section: Introductionmentioning

confidence: 99%

Intensification and deepening of the Arabian Sea Oxygen Minimum Zone in response to increase in Indian monsoon wind intensity

Lachkar¹,

Smith²,

Lévy³

2017

Preprint

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Abstract. The decline in oxygen supply to the ocean associated with global warming is expected to expand oxygen minimum zones (OMZs). This global trend can be attenuated or amplified by regional processes. In the Arabian Sea, the World&#8217;s thickest OMZ is highly vulnerable to changes in the Indian monsoon wind. Evidence from paleo records and future climate projections indicate strong variations of the Indian monsoon wind intensity over climatic timescales. Yet, the response of the OMZ to these wind changes remains poorly understood and its amplitude and timescale unexplored. Here, we investigate the impacts of perturbations in Indian monsoon wind intensity (from &#8722;50&#8201;% to +50&#8201;%) on the size and intensity of the Arabian Sea OMZ, and examine the biogeochemical and ecological implications of these changes. To this end, we conducted a series of eddy-resolving simulations of the Arabian Sea using the Regional Oceanic Modeling System (ROMS) coupled to a nitrogen based Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD) ecosystem model that includes a representation of the O2 cycle. We show that the Arabian Sea productivity increases and its OMZ expands and deepens in response to monsoon wind intensification. These responses are dominated by the perturbation of the summer monsoon wind, whereas the changes in the winter monsoon wind play a secondary role. While the productivity responds quickly and nearly linearly to wind increase (i.e., on a timescale of years), the OMZ response is much slower (i.e., a timescale of decades). Our analysis reveals that the OMZ expansion at depth is driven by increased oxygen biological consumption, whereas its surface weakening is induced by increased ventilation. The enhanced ventilation favors episodic intrusions of oxic waters in the lower epipelagic zone (100&#8211;200&#8201;m) of the western and central Arabian Sea, leading to intermittent expansions of marine habitats and a more frequent alternation of hypoxic and oxic conditions there. The increased productivity and deepening of the OMZ also lead to a strong intensification of denitrification at depth, resulting in a substantial amplification of fixed nitrogen depletion in the Arabian Sea. We conclude that changes in the Indian monsoon can affect, on longer timescales, the large-scale biogeochemical cycles of nitrogen and carbon, with a positive feedback on climate change in the case of stronger winds.

show abstract

Intensification of upwelling along Oman coast in a warming scenario

Cited by 41 publications

References 39 publications

Intensification and deepening of the Arabian Sea oxygen minimum zone in response to increase in Indian monsoon wind intensity

Intensification and deepening of the Arabian Sea oxygen minimum zone in response to increase in Indian monsoon wind intensity

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Intensification and deepening of the Arabian Sea Oxygen Minimum Zone in response to increase in Indian monsoon wind intensity

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