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1 The main scientific drivers of the Indian Ocean Observing System, including the Oxygen Minimum Zones (OMZs), upwelling and subduction zones, major heat flux components, the tropical modes of the Madden-Julian Oscillation (MJO), the Monsoon Intra-Seasonal Oscillation (MISO), the Indian Ocean Dipole (IOD) and Indian Ocean Basin Mode (IOBM), the subtropical modes of Ningaloo Niño and subtropical IOD, cyclogenesis, and climate change.

1 The main scientific drivers of the Indian Ocean Observing System, including the Oxygen Minimum Zones (OMZs), upwelling and subduction zones, major heat flux components, the tropical modes of the Madden-Julian Oscillation (MJO), the Monsoon Intra-Seasonal Oscillation (MISO), the Indian Ocean Dipole (IOD) and Indian Ocean Basin Mode (IOBM), the subtropical modes of Ningaloo Niño and subtropical IOD, cyclogenesis, and climate change.

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Book
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Full Report of IndOOS-2. The Indian Ocean Observing System (IndOOS) is a network of all the sustained observations in the Indian Ocean. Here we present IndOOS-2, designed for the future, to address changing societal and scientific priorities.

Citations

... Recent decades have observed warming of the earth's climate unequivocally, with the oceans accounting for approximately 93% of this increased energy uptake 12,13 . Amongst the tropical oceans, the Indian Ocean has undergone the largest warming (0.15 °C/decade) in ocean surface 11,14,15 , with projections of a stronger warming (> 1.5 °C) by 2070 and (> 2.5 °C) by 2100 across the CMIP5 models 16,17 . In the low-latitude regions, a warmer ocean surface enhances the ocean stratification thereby reducing the vertical mixing and inhibiting the nutrients (required for photosynthesis) into the sunlit zone of the ocean 18,19 . ...
Article
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Continuous remote-sensed daily fields of ocean color now span over two decades; however, it still remains a challenge to examine the ocean ecosystem processes, e.g., phenology, at temporal frequencies of less than a month. This is due to the presence of significantly large gaps in satellite data caused by clouds, sun-glint, and hardware failure; thus, making gap-filling a prerequisite. Commonly used techniques of gap-filling are limited to single value imputation, thus ignoring the error estimates. Though convenient for datasets with fewer missing pixels, these techniques introduce potential biases in datasets having a higher percentage of gaps, such as in the tropical Indian Ocean during the summer monsoon, the satellite coverage is reduced up to 40% due to the seasonally varying cloud cover. In this study, we fill the missing values in the tropical Indian Ocean with a set of plausible values (here, 10,000) using the classical Monte-Carlo method and prepare 10,000 gap-filled datasets of ocean color. Using the Monte-Carlo method for gap-filling provides the advantage to estimate the phenological indicators with an uncertainty range, to indicate the likelihood of estimates. Quantification of uncertainty arising due to missing values is critical to address the importance of underlying datasets and hence, motivating future observations.
... It was observed that the heat content has also risen in the upper IOR since 1950sandthere has been a sudden rise in the trend since 2000 (Roxy, Gnanaseelan, Parekh, et al. 2020). An assessment of the data, from 1870 to 2007, of monthly SST along the ship tracks from Gulf of Aden through the Malacca Strait reveals a 1.4°C temperature rise during the period in the region (Beal, Vialard, Roxy,et al. 2019). The reason for this higher warming is attributed to anthropogenic emissions. ...
... In north Indian Ocean, the SCSs, super cyclonic storms, and depressions are found to increase in recent years compared to cyclonic storms (CSs) and deep depressions (Dee, Uppala, Simmons,et al. 2011). The Bay of Bengal region accounts for almost 80% of the global fatalities due to tropical cyclones (TCs) alone in IOR (Beal, Vialard, Roxy,et al. 2019). ...
... Figure 13 shows the status of India Ocean Observation System (IndOOS) in 2018, comprising Argo, RAMA, XBT/XCTD, surface drifting buoy, and tide gauge networks. It is supported by satellite observations and the GO-SHIP program (Beal, Vialard, Roxy,et al. 2019). ...
Book
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The book has been a culmination of joint efforts and initiatives by Konrad Adeanuer Stiftung India office, The Energy and Resources Institute (TERI), National Maritime Foundation (NMF) and Federation of Indian Chambers of Commerce and Industry (FICCI) to nurture and encourage a holistic discourse on Blue economy in India. FICCI, NMF and TERI with the partnership of KAS India collaborated to bring together eminent voices and thinkers on blue economy with six webinars and a hybrid national conference focusing on establishing synergies, a multidisciplinary approach and augmenting discussions for a cohesive perspective on blue economy. The focus of the book has been to build a collective dialogue on the three pillars of blue economy – maritime security, economic growth and sustainable development. The book has several chapters written by different experts from varied facets of blue economy. As the Editor and Coordinator of the Book, I am immensely thankful to all authors for their contributions.
... Therefore, the in-situ observations of surface salinity during the cyclone also need to be improved as satellites fail to sense the salinity variations of the upper ocean due to deep convective clouds during the time of cyclone. Currently, there are only two satellite scatterometers that provide approximately 60% coverage of the ocean at 6-hourly interval, the decorrelation time scale of the diurnal cycle (Beal et al., 2019). The spatial and temporal coverage of satellite-derived winds and wind stress estimates over the open ocean needs to be increased especially at the time of a cyclone as it will give a better idea about the ocean-atmosphere coupling and diurnal variations during the cyclone. ...
Article
The north Indian Ocean accounts for 6% of the global tropical cyclones annually. Despite the small fraction of cyclones, some of the most devastating cyclones have formed in this basin, causing extensive damage to the life and property in the north Indian Ocean rim countries. In this review article, we highlight the advancement in research in terms of ocean-atmosphere interaction during cyclones in the north Indian Ocean and identify the gap areas where our understanding is still lacking. There is a two-way ocean-atmosphere interaction during cyclones in the north Indian Ocean. High sea surface temperatures (SSTs) of magnitude 28–29 °C and above provide favorable conditions for the genesis and evolution of cyclones in the Arabian Sea and the Bay of Bengal. On the other hand, cyclones induce cold and salty wakes. Cyclone induced cooling depends on the translation speed of the cyclone, wind power input, ocean stratification, and the subsurface conditions dictated by the ocean eddies, mixed layer and the barrier layer in the north Indian Ocean. The average cyclone-induced SST cooling is 2–3 °C during the pre-monsoon season and 0.5–1 °C during the post-monsoon season. This varying ocean response to cyclones in the two seasons in the Bay of Bengal is due to the difference in the ocean haline stratification, whereas, in the Arabian Sea it is due to the difference in cyclone wind power input and ocean thermal stratification. The oceanic response to cyclone is asymmetric due to the asymmetry in the cyclone wind stress, cyclone induced rainfall and the dynamics of the ocean inertial currents. The cyclone induced wake is salty and is the saltiest in the Bay of Bengal among all the ocean basins. The physical response of the ocean to the cyclone is accompanied by a biological response also, as cyclones induce large chlorophyll blooms in the north Indian Ocean that last from several days to weeks. SSTs leading to cyclogenesis in the Arabian Sea are 1.2–1.4 °C higher in the recent decades, compared to SSTs four decades ago. Rapid warming in the north Indian Ocean, associated with global warming, tends to enhance the heat flux from the ocean to the atmosphere and favor rapid intensification of cyclones. Monitoring and forecasting rapid intensification is a challenge, particularly due to gaps in in-situ ocean observations. Changes in ocean-cyclone interactions are emerging in recent decades in response to Indian Ocean warming, and are to be closely monitored with improved observations since future climate projections demonstrate continued warming of the Indian Ocean at a rapid pace along with an increase in the intensity of cyclones in this basin.
... Broader coverage of the maritime domain reduces the risk of natural resource degradation, exploitation and illegal activity (Lindstrom et al., 2012;Visbeck, 2018;Claudet et al., 2020), particularly in large ocean nations (United Nations, 2015;Dunn et al., 2018) and areas beyond national jurisdictions (Cremers et al., 2020;United Nations, 2021). High spatiotemporal coverage for metocean data collection is fundamental to the sustainable management of our oceans (Beal et al., 2019;Smith et al., 2019;Friedman et al., 2020). Increased ocean coverage is an internationally agreed goal, underpinning the United Nations Sustainable Development Goals (United Nations, 2015) and Decade of Ocean Science for Sustainable Development (Ryabinin et al., 2019). ...
Article
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Accessing the world's oceans is essential for monitoring and sustainable management of the maritime domain. Difficulty in reaching remote locations has resulted in sparse coverage, undermining our capacity to deter illegal activities and gather data for physical and biological processes. Uncrewed Surface Vessels (USVs) have existed for over two decades and offer the potential to overcome difficulties associated with monitoring and surveillance in remote regions. However, they are not yet an integral component of maritime infrastructure. We analyse 15 years of non-autonomous and semi-autonomous USV-related literature to determine the factors limiting technological diffusion into everyday maritime operations. We systematically categorised over 1,000 USV-related publications to determine how government, academia and industry sectors use USVs and what drives their uptake. We found a striking overlap between these sectors for 11 applications and nine drivers. Low cost was a consistent and central driver for USV uptake across the three sectors. Product ‘compatibility' and lack of ‘complexity' appear to be major factors limiting USV technological diffusion amongst early adopters. We found that the majority (21 of 27) of commercially available USVs lacked the complexity required for multiple applications in beyond the horizon operations. We argue that the best value for money to advance USV uptake is for designs that offer cross-disciplinary applications and the ability to operate in an unsheltered open ocean without an escort or mothership. The benefits from this technological advancement can excel under existing collaborative governance frameworks and are most significant for remote and developing maritime nations.
... The Indian Ocean rim countries, accounting for one-third of the Earth's human population, depend on this ocean for food and resources and are dramatically impacted by its variability . Increasing our understanding of in-teractions between geologic, oceanic, and atmospheric processes that control the complex physical dynamics of the Indian Ocean region is a priority for many national, bilateral, and international programmes, including the Indian Ocean Observing System (IndOOS; Beal et al., 2020), the Climate and Ocean: Variability, Predictability and Change (CLIVAR)/Intergovernmental Oceanographic Commission (IOC) -Indian Ocean Region Panel (https://www.clivar.org/ sites/default/files/documents/indian/135_IOP5.pdf, last access: 22 October 2021), and the second International Indian Ocean Expedition (IIOE-2), to name a few. ...
... Recent focus on the Indian Ocean has motivated new international efforts in field campaigns and modelling studies and leveraged advances in global observations that contribute to the Indian Ocean Observing System (IndOOS; Beal et al., 2020). The Argo profiling float array (Roemmich et al., 2012) reached full coverage in the Indian Ocean in 2006, the Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction (RAMA) moored buoy array (McPhaden et al., 2009) has now delivered multi-year time series of tropical oceanic and atmospheric variability, with some sites dating back to 2000. ...
... Variability in the oceanic and atmospheric circulation of the Indian Ocean is the result of complex interactions that are both internal and external to the Indian Ocean. The recent review of the IndOOS plan (Beal et al., , 2020 summarizes the major scientific drivers, of which we still have limited understanding (Fig. 1). The overarching signal is anthropogenic climate change, causing a background trend of ocean warming and increasing acidity due to uptake of heat and carbon dioxide and affecting the nature of large-and small-scale variability mechanisms. ...
Article
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Over the past decade, our understanding of the Indian Ocean has advanced through concerted efforts toward measuring the ocean circulation and air–sea exchanges, detecting changes in water masses, and linking physical processes to ecologically important variables. New circulation pathways and mechanisms have been discovered that control atmospheric and oceanic mean state and variability. This review brings together new understanding of the ocean–atmosphere system in the Indian Ocean since the last comprehensive review, describing the Indian Ocean circulation patterns, air–sea interactions, and climate variability. Coordinated international focus on the Indian Ocean has motivated the application of new technologies to deliver higher-resolution observations and models of Indian Ocean processes. As a result we are discovering the importance of small-scale processes in setting the large-scale gradients and circulation, interactions between physical and biogeochemical processes, interactions between boundary currents and the interior, and interactions between the surface and the deep ocean. A newly discovered regional climate mode in the southeast Indian Ocean, the Ningaloo Niño, has instigated more regional air–sea coupling and marine heatwave research in the global oceans. In the last decade, we have seen rapid warming of the Indian Ocean overlaid with extremes in the form of marine heatwaves. These events have motivated studies that have delivered new insight into the variability in ocean heat content and exchanges in the Indian Ocean and have highlighted the critical role of the Indian Ocean as a clearing house for anthropogenic heat. This synthesis paper reviews the advances in these areas in the last decade.
... Therefore, the in-situ observations of surface salinity during the cyclone also need to be improved as satellites fail to sense the salinity variations of the upper ocean due to deep convective clouds during the time of cyclone. Currently, there are only two satellite scatterometers that provide approximately 60% coverage of the ocean at 6-hourly interval, the de-correlation time scale of the diurnal cycle (Beal et al. 2019). The spatial and temporal coverage of satellite-derived winds and wind stress estimates over the open ocean needs to be increased especially at the time of a cyclone as it will give a better idea about the ocean-atmosphere coupling and diurnal variations during the cyclone. ...
Preprint
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The north Indian Ocean accounts for 6% of the global tropical cyclones annually. Despite the small fraction of cyclones, some of the most devastating cyclones have formed in this basin, causing extensive damage to the life and property in the north Indian Ocean rim countries. In this review article, we highlight the advancement in research in terms of ocean-atmosphere interaction during cyclones in the north Indian Ocean and identify the gap areas where our understanding is still lacking. Preprint of the article submitted to Earth Science Reviews.
Preprint
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Extreme weather events often trigger massive population displacement. A compounding factor is that the frequency and intensity of such events is affected by anthropogenic climate change. However, the effect of historical climate change on displacement risk has so far not been quantified. Here, we show how displacement can be partially attributed to climate change, using the example of the 2019 tropical cyclone Idai in Mozambique. We estimate the population exposed to flooding following Idai’s landfall, using a combination of storm surge modeling and flood depth estimation from remote sensing images, for factual (climate change) and counterfactual (no climate change) mean sea level and maximum wind speed conditions. We find that climate change has increased displacement risk from this event by approximately 3.1 to 3.5 %, corresponding to 16,000–17,000 additional displaced persons. Besides highlighting the significant effects on humanitarian conditions already imparted by climate change, our study provides a blueprint for event-based displacement attribution.
Article
The heat content in the Indian Ocean has been increasing owing to anthropogenic greenhouse warming. Yet, where and how the anthropogenic heat is stored in the Indian Ocean have not been comprehended. Analysis of various observational and model-based datasets since the 1950s reveals a robust spatial pattern of the 0-700 m ocean heat content trend (ΔOHC), with enhanced warming in the subtropical southern Indian Ocean (SIO) but weak to minimal warming in the tropical Indian Ocean (TIO). The meridional temperature gradient between the TIO and SIO declined by 16.4%±7.5% during 1958-2014. The heat redistribution driven by time-varying surface winds plays a crucial role in shaping this ΔOHC pattern. Sensitivity experiments using a simplified ocean dynamical model suggest that changes in surface winds over the Indian Ocean, particularly those of the SIO, caused a convergence trend in the upper SIO and a divergence trend in the upper TIO. These wind changes primarily include the enhancements of westerlies in the Southern Ocean and the subtropical anticyclone in the SIO. Albeit with systematic biases, the ΔOHC pattern and surface wind changes simulated by Coupled Model Intercomparison Project Phase-6 (CMIP6) models broadly resemble the observation and highlight the essence of external forcing in causing these changes. This heat storage pattern is projected to persist in the model-projected future, potentially impacting future climate.
Article
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This study was carried out to monitor the shoreline changes and associated erosion along the coastal districts using multi-temporal Landsat digital data over the period from 1978 to 2020. The High Tide Line was delineated using Landsat Satellite data from 1978, 1998, and 2020 based on various geomorphologic and land use/cover types. The extent of the coastline erosion at two continuous decades intervals, and the total during 42 years from 1978 to 2020 was delineated, and in the coastline, erosion was monitored. The analysis indicated that the highest coastal erosion took place in the Kachchh district. The results of this study indicate that about 723.6 km is subjected to erosion, which is almost 45.9% of the total Gujarat coastline. A gradual increasing trend was observed in SST from 1860 to 2020 along with the increase in CO2 emission for the period of 50 years (1960-2010). The analysis of variation in the normalized SST with annual mean sunspot activity from 1960 to 2020 revealed that the peak of SST follows the peak of annual mean sunspot activity till 2000. However, the solar activity declined significantly since 2000 and the annual mean sunspot number decreased until 2020, while on the contrary, the SST showed an increasing trend.
Article
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The Indian Ocean is warming rapidly, with widespread effects on regional weather and global climate. Sea‐surface temperature records indicate this warming trend extends back to the beginning of the 20th century, however the lack of a similarly long instrumental record of interior ocean temperatures leaves uncertainty around the subsurface trends. Here we utilize unique temperature observations from three historical German oceanographic expeditions of the late 19th and early 20th centuries: SMS Gazelle (1874–1876), Valdivia (1898–1899), and SMS Planet (1906–1907). These observations reveal a mean 20th century ocean warming that extends over the upper 750 m, and a spatial pattern of subsurface warming and cooling consistent with a 1°–2° southward shift of the southern subtropical gyre. These interior changes occurred largely over the last half of the 20th century, providing observational evidence for the acceleration of a multidecadal trend in subsurface Indian Ocean temperature.