The impact of thermohaline staircases: estimates from a global analysis of Argo floats

2020 ◽  
Author(s):  
Carine van der Boog ◽  
Julie D Pietrzak ◽  
Henk A Dijkstra ◽  
Caroline A Katsman
Keyword(s):  
Heat Transfer ◽  
Indian Ocean ◽  
Atlantic Ocean ◽  
Water Mass ◽  
Double Diffusion ◽  
The Indian Ocean ◽  
Diffusive Processes ◽  
The Impact ◽  
Double Diffusive ◽  
Water Mass Transformation

<p>Thermohaline staircases are stepped structures in the temperature and salinity stratification that result from double diffusive processes. In the open ocean, double diffusive processes enhance the downgradient diapycnal heat transfer compared to turbulent mixing. However, in combination with salinity effects, the resulting buoyancy flux within the thermohaline staircases is counter gradient. This vertical density transport strengthens the stratification and, consequently, affects the density of the water masses above and below the staircase layer. Although 44 percent of the world’s oceans is susceptible to double diffusion and thermohaline staircases are ubiquitous in these regions, the impact of double diffusion on diapycnal heat transfer and on water mass transformation has not been quantified yet. Here, we analyse a dataset of Argo float profiles to obtain a global overview of the occurrence of thermohaline staircases and to estimate their impact on diapycnal heat transfer and water mass transformation. Several regions with a high staircase occurrence are identified. Besides the well-known regions in the Caribbean Sea, the Mediterranean Sea and the subtropical Atlantic Ocean, our analysis reveals a new staircase region in the Indian Ocean. Using this global overview, we estimate, for the first time, the contribution of downgradient diapycnal heat transfer by the staircases. It appears that this contribution is very low compared to the dissipation required to maintain the observed temperature stratification. However, each staircase region can potentially impact the global circulation by affecting the density of the water masses above and below. In particular, the staircase region in the Indian Ocean overlies the waters of the Tasman Leakage. These waters flow westward from Australia towards the Agulhas region and affect the properties of waters entering the Atlantic Ocean. This implies that the vertical flux of salt into the Tasman Leakage waters induced by the presence of thermohaline staircases above can impact the salt transport into the Atlantic Ocean, which in turn is expected to impact the Atlantic Meridional Overturning Circulation. </p>

scholarly journals Spatiotemporal Evolution and Determinant Factors of the Intra-Regional Trade Community Structures of the Indian Ocean Region

2021 ◽  
Vol 10 (4) ◽  
pp. 214
Author(s):  
Lihua Yuan ◽  
Xiaoqiang Chen ◽  
Changqing Song ◽  
Danping Cao ◽  
Hong Yi
Keyword(s):  
Indian Ocean ◽  
Explanatory Power ◽  
Community Structures ◽  
Indian Ocean Region ◽  
Spatiotemporal Evolution ◽  
Regional Trade ◽  
Determinant Factors ◽  
Ocean Region ◽  
The Indian Ocean ◽  
The Impact

The Indian Ocean Region (IOR) has become one of the main economic forces globally, and countries within the IOR have attempted to promote their intra-regional trade. This study investigates the spatiotemporal evolution of the community structures of the intra-regional trade and the impact of determinant factors on the formation of trade community structures of the IOR from 1996 to 2017 using the methods of social network analysis. Trade communities are groups of countries with measurably denser intra-trade ties but with extra-trade ties that are measurably sparser among different communities. The results show that the extent of trade integration and the trade community structures of the IOR changed from strengthening between 1996 and 2014 to weakening between 2015 and 2017. The largest explanatory power of the formation of the IOR trade community structures was the IOR countries’ economic size, indicating that market remained the strongest driver. The second-largest explanatory power was geographical proximity, suggesting that countries within the IOR engaged in intra-regional trade still tended to select geographically proximate trading partners. The third- and the fourth-largest were common civilization and regional organizational memberships, respectively. This indicates that sharing a common civilization and constructing intra-regional institutional arrangements (especially open trade policies) helped the countries within the IOR strengthen their trade communities.

scholarly journals Research Gap Analysis of Remote Sensing Application in Fisheries: Prospects for Achieving the Sustainable Development Goals

2021 ◽  
Vol 13 (5) ◽  
pp. 1013
Author(s):  
Kuo-Wei Yen ◽  
Chia-Hsiang Chen
Keyword(s):  
Sustainable Development ◽  
Indian Ocean ◽  
Atlantic Ocean ◽  
The Sustainable Development ◽  
The North ◽  
The Pacific ◽  
Development Goals ◽  
The Indian Ocean ◽  
The Pacific Ocean ◽  
Research Hotspots

Remote sensing (RS) technology, which can facilitate the sustainable management and development of fisheries, is easily accessible and exhibits high performance. It only requires the collection of sufficient information, establishment of databases and input of human and capital resources for analysis. However, many countries are unable to effectively ensure the sustainable development of marine fisheries due to technological limitations. The main challenge is the gap in the conditions for sustainable development between developed and developing countries. Therefore, this study applied the Web of Science database and geographic information systems to analyze the gaps in fisheries science in various countries over the past 10 years. Most studies have been conducted in the offshore marine areas of the northeastern United States of America. In addition, all research hotspots were located in the Northern Hemisphere, indicating a lack of relevant studies from the Southern Hemisphere. This study also found that research hotspots of satellite RS applications in fisheries were mainly conducted in (1) the northeastern sea area in the United States, (2) the high seas area of the North Atlantic Ocean, (3) the surrounding sea areas of France, Spain and Portugal, (4) the surrounding areas of the Indian Ocean and (5) the East China Sea, Yellow Sea and Bohai Bay sea areas to the north of Taiwan. A comparison of publications examining the three major oceans indicated that the Atlantic Ocean was the most extensively studied in terms of RS applications in fisheries, followed by the Indian Ocean, while the Pacific Ocean was less studied than the aforementioned two regions. In addition, all research hotspots were located in the Northern Hemisphere, indicating a lack of relevant studies from the Southern Hemisphere. The Atlantic Ocean and the Indian Ocean have been the subjects of many local in-depth studies; in the Pacific Ocean, the coastal areas have been abundantly investigated, while offshore local areas have only been sporadically addressed. Collaboration and partnership constitute an efficient approach for transferring skills and technology across countries. For the achievement of the sustainable development goals (SDGs) by 2030, research networks can be expanded to mitigate the research gaps and improve the sustainability of marine fisheries resources.

scholarly journals The Impact of Parental Death on Child Well-being: Evidence from the Indian Ocean Tsunami

2013 ◽  
Author(s):  
Ava Cas ◽  
Elizabeth Frankenberg ◽  
Wayan Suriastini ◽  
Duncan Thomas
Keyword(s):  
Indian Ocean ◽  
Parental Death ◽  
Well Being ◽  
Indian Ocean Tsunami ◽  
The Indian Ocean ◽  
The Impact

scholarly journals An integrated social response to disasters: the case of the Indian Ocean tsunami in Sri Lanka

2016 ◽  
Vol 25 (5) ◽  
pp. 595-610 ◽  
Author(s):  
Siri Hettige ◽  
Richard Haigh
Keyword(s):  
Sri Lanka ◽  
Indian Ocean ◽  
Disaster Recovery ◽  
Mode Of Delivery ◽  
Recovery Process ◽  
Qualitative Assessment ◽  
Indian Ocean Tsunami ◽  
Content Type ◽  
The Indian Ocean ◽  
The Impact

Purpose The impact of disasters caused by natural hazards on people in affected communities is mediated by a whole range of circumstances such as the intensity of the disaster, type and nature of the community affected and the nature of loss and displacement. The purpose of this paper is to demonstrate the need to adopt a holistic or integrated approach to assessment of the process of disaster recovery, and to develop a multidimensional assessment framework. Design/methodology/approach The study is designed as a novel qualitative assessment of the recovery process using qualitative data collection techniques from a sample of communities affected by the Indian Ocean tsunami in Eastern and Southern Sri Lanka. Findings The outcomes of the interventions have varied widely depending on such factors as the nature of the community, the nature of the intervention and the mode of delivery for donor support. The surveyed communities are ranked in terms of the nature and extent of recovery. Practical implications The indices of recovery developed constitute a convenient tool of measurement of effectiveness and limitations of external interventions. The assessment used is multidimensional and socially inclusive. Originality/value The approach adopted is new to post-disaster recovery assessments and is useful for monitoring and evaluation of recovery processes. It also fits into the social accountability model as the assessment is based on community experience with the recovery process.

scholarly journals The Linear Sensitivity of the North Atlantic Oscillation and Eddy-Driven Jet to SSTs

2019 ◽  
Vol 32 (19) ◽  
pp. 6491-6511 ◽  
Author(s):  
Hugh S. Baker ◽  
Tim Woollings ◽  
Chris E. Forest ◽  
Myles R. Allen
Keyword(s):  
Indian Ocean ◽  
North Atlantic Oscillation ◽  
North Atlantic ◽  
High Sensitivity ◽  
Internal Variability ◽  
The North ◽  
The Indian Ocean ◽  
The North Atlantic ◽  
The North Atlantic Oscillation ◽  
The Impact

Abstract The North Atlantic Oscillation (NAO) and eddy-driven jet contain a forced component arising from sea surface temperature (SST) variations. Due to large amounts of internal variability, it is not trivial to determine where and to what extent SSTs force the NAO and jet. A linear statistical–dynamic method is employed with a large climate ensemble to compute the sensitivities of the winter and summer NAO and jet speed and latitude to the SSTs. Key regions of sensitivity are identified in the Indian and Pacific basins, and the North Atlantic tripole. Using the sensitivity maps and a long observational SST dataset, skillful reconstructions of the NAO and jet time series are made. The ability to skillfully forecast both the winter and summer NAO using only SST anomalies is also demonstrated. The linear approach used here allows precise attribution of model forecast signals to SSTs in particular regions. Skill comes from the Atlantic and Pacific basins on short lead times, while the Indian Ocean SSTs may contribute to the longer-term NAO trend. However, despite the region of high sensitivity in the Indian Ocean, SSTs here do not provide significant skill on interannual time scales, which highlights the limitations of the imposed SST approach. Given the impact of the NAO and jet on Northern Hemisphere weather and climate, these results provide useful information that could be used for improved attribution and forecasting.

Recent Atmospheric Variability at Kibo Summit, Kilimanjaro, and Its Relation to Climate Mode Activity

2018 ◽  
Vol 31 (10) ◽  
pp. 3875-3891 ◽  
Author(s):  
Emily Collier ◽  
Thomas Mölg ◽  
Tobias Sauter
Keyword(s):  
Indian Ocean ◽  
Current Knowledge ◽  
Southern Oscillation ◽  
Strong Association ◽  
Atmospheric Modeling ◽  
High Mountain ◽  
Atmospheric Variability ◽  
Rain Season ◽  
The Indian Ocean ◽  
The Impact

Abstract Accurate knowledge of the impact of internal atmospheric variability is required for the detection and attribution of climate change and for interpreting glacier records. However, current knowledge of such impacts in high-mountain regions is largely based on statistical methods, as the observational data required for process-based assessments are often spatially or temporally deficient. Using a case study of Kilimanjaro, 12 years of convection-permitting atmospheric modeling are combined with an 8-yr observational record to evaluate the impact of climate oscillations on recent high-altitude atmospheric variability during the short rains (the secondary rain season in the region). The focus is on two modes that have a well-established relationship with precipitation during this season, El Niño–Southern Oscillation and the Indian Ocean zonal mode, and demonstrate their strong association with local and mesoscale conditions at Kilimanjaro. Both oscillations correlate positively with humidity fluctuations, but the association is strongest with the Indian Ocean zonal mode in the air layers near and above the glaciers because of changes in zonal circulation and moisture transport, emphasizing the importance of the moisture signal from this basin. However, the most anomalous conditions are found during co-occurring positive events because of the combined effects of the (i) extended positive sea surface temperature anomalies, (ii) enhanced atmospheric moisture capacity from higher tropospheric temperatures, (iii) most pronounced weakening of the subsiding branch of the Indian Ocean Walker circulation over East Africa, and (iv) stronger monsoonal moisture fluxes upstream from Kilimanjaro. This study lays the foundation for unraveling the contribution of climate modes to observed changes in Kilimanjaro’s glaciers.

“Oceans without Borders”: Dialectics of Transcolonial Labor Migration from the Indian Ocean World to the Atlantic Ocean World

2015 ◽  
Vol 87 ◽  
pp. 7-26 ◽  
Author(s):  
Yoshina Hurgobin ◽  
Subho Basu
Keyword(s):  
Indian Ocean ◽  
Atlantic Ocean ◽  
Labor Migration ◽  
Indentured Labor ◽  
Crucial Component ◽  
Global Demand ◽  
The Indian Ocean ◽  
In Trans ◽  
The Caribbean ◽  
Indian Ocean World

AbstractBy investigating the hitherto unstudied trans-colonial migration between Mauritius and the Caribbean in the nineteenth century, this article complicates liberal Eurocentric perceptions of global labor force formation under the auspices of colonial capital. Indeed, coercion, as depicted in liberal historiography, was a crucial component of indentured migration but indentured workers themselves sometimes availed of the opportunity of the global demand for their labor by engaging in trans-colonial migration. The dialectic of the formation of globalized indentured labor regime was such that while capital sought to confine workers to specific plantations, the very nature of the demand for labor enabled workers to defy the dictates of capital and further enabled them to move from one colony to another in search of better livelihoods and thus made them globally mobile. These migrations did not follow the so-called boundaries between the Indian Ocean and the Atlantic Ocean. Rather such migrations reflected workers’ search for jobs through trans-colonial networks within the framework of imperial domination.

scholarly journals Impact of the Madden–Julian Oscillation on Summer Rainfall in Southeast China

2009 ◽  
Vol 22 (2) ◽  
pp. 201-216 ◽  
Author(s):  
Lina Zhang ◽  
Bizheng Wang ◽  
Qingcun Zeng
Keyword(s):  
Indian Ocean ◽  
Tropical Indian Ocean ◽  
Summer Rainfall ◽  
Western Pacific ◽  
Madden Julian Oscillation ◽  
Energy Propagation ◽  
Southeast China ◽  
The Indian Ocean ◽  
The Impact ◽  
The Western Pacific

Abstract The impact of the Madden–Julian oscillation (MJO) on summer rainfall in Southeast China is investigated using the Real-time Multivariate MJO (RMM) index and the observational rainfall data. A marked transition of rainfall patterns from being enhanced to being suppressed is found in Southeast China (east of 105°E and south of 35°N) on intraseasonal time scales as the MJO convective center moves from the Indian Ocean to the western Pacific Ocean. The maximum positive and negative anomalies of regional mean rainfall are in excess of 10% relative to the climatological regional mean. Such different rainfall regimes are associated with the corresponding changes in physical fields such as the western Pacific subtropical high (WPSH), moisture, and vertical motions. When the MJO is mainly over the Indian Ocean, the WPSH shifts farther westward, and the moisture and upward motions in Southeast China are increased. In contrast, when the MJO enters the western Pacific, the WPSH retreats eastward, and the moisture and upward motions in Southeast China are decreased. It is suggested that the MJO may influence summer rainfall in Southeast China through remote and local dynamical mechanisms, which correspond to the rainfall enhancement and suppression, respectively. The remote role is the energy propagation of the Rossby wave forced by the MJO-related heating over the Indian Ocean through the low-level westerly waveguide from the tropical Indian Ocean to Southeast China. The local role is the northward shift of the upward branch of the anomalous meridional circulation when the MJO is over the western Pacific, which causes eastward retreat of the WPSH and suppressed moisture transport toward Southeast China.

scholarly journals Population trends and conservation status of the Northern Rockhopper PenguinEudyptes moseleyiat Tristan da Cunha and Gough Island

2009 ◽  
Vol 19 (1) ◽  
pp. 109-120 ◽  
Author(s):  
RICHARD CUTHBERT ◽  
JOHN COOPER ◽  
MARIE-HELENE BURLE ◽  
CONRAD J. GLASS ◽  
JAMES P. GLASS ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Conservation Status ◽  
Sharp Decrease ◽  
Population Trends ◽  
Tristan Da Cunha ◽  
Fur Seals ◽  
Introduced Predators ◽  
Gough Island ◽  
The Indian Ocean ◽  
The Impact

SummaryPopulations of the recently split Northern Rockhopper PenguinEudyptes moseleyiare restricted to Tristan da Cunha and Gough Island in the South Atlantic, and Amsterdam and St Paul in the Indian Ocean. The majority of the population is in the Atlantic (> 80%), but population trends at Tristan da Cunha and Gough are uncertain. Early records indicate “millions” of penguins used to occur at Tristan da Cunha and Gough Island. The most recent estimates indicate declines in excess of 90% for both Gough and the main island of Tristan that have occurred over at least 45 and 130 years, respectively. Numbers breeding at Inaccessible and Nightingale islands (TDC) also may have declined since the 1970s, albeit modestly, whereas numbers on Tristan appear stable over the last few decades. Current population estimates are 32,000–65,000 pairs at Gough, 18–27,000 at Inaccessible, 19,500 at Nightingale, and 3,200–4,500 at Tristan. Numbers and trends at Middle Island (TDC) are unknown. Middle Island supported an estimated 100,000 pairs in 1973, and recent observations suggest this colony is being impacted by competition for space with recently recolonising Subantarctic Fur SealsArctocephalus tropicalis. Past human exploitation and the impact of introduced predators may be responsible for the historical decline in numbers at Tristan, but these factors cannot explain the sharp decrease (since the 1950s) at Gough Island. Overall, declines at Gough, Tristan, Nightingale and Inaccessible islands indicate a three-generation decline of > 50%. Taken in combination with recent decreases in Indian Ocean populations, the Northern Rockhopper Penguins is now categorised as globally ‘Endangered’. Determining the causal factors responsible for these recent declines is an urgent priority.

Impact of Indo-Pacific Feedback Interactions on ENSO Dynamics Diagnosed Using Ensemble Climate Simulations

2012 ◽  
Vol 25 (21) ◽  
pp. 7743-7763 ◽  
Author(s):  
A. Santoso ◽  
M. H. England ◽  
W. Cai
Keyword(s):  
Indian Ocean ◽  
Climate Model ◽  
Southern Oscillation ◽  
Ocean Basin ◽  
Climate Feedback ◽  
Enso Events ◽  
Thermocline Feedback ◽  
Enso Dynamics ◽  
The Indian Ocean ◽  
The Impact

The impact of Indo-Pacific climate feedback on the dynamics of El Niño–Southern Oscillation (ENSO) is investigated using an ensemble set of Indian Ocean decoupling experiments (DCPL), utilizing a millennial integration of a coupled climate model. It is found that eliminating air–sea interactions over the Indian Ocean results in various degrees of ENSO amplification across DCPL simulations, with a shift in the underlying dynamics toward a more prominent thermocline mode. The DCPL experiments reveal that the net effect of the Indian Ocean in the control runs (CTRL) is a damping of ENSO. The extent of this damping appears to be negatively correlated to the coherence between ENSO and the Indian Ocean dipole (IOD). This type of relationship can arise from the long-lasting ENSO events that the model simulates, such that developing ENSO often coincides with Indian Ocean basin-wide mode (IOBM) anomalies during non-IOD years. As demonstrated via AGCM experiments, the IOBM enhances western Pacific wind anomalies that counteract the ENSO-enhancing winds farther east. In the recharge oscillator framework, this weakens the equatorial Pacific air–sea coupling that governs the ENSO thermocline feedback. Relative to the IOBM, the IOD is more conducive for ENSO growth. The net damping by the Indian Ocean in CTRL is thus dominated by the IOBM effect which is weaker with stronger ENSO–IOD coherence. The stronger ENSO thermocline mode in DCPL is consistent with the absence of any IOBM anomalies. This study supports the notion that the Indian Ocean should be viewed as an integral part of ENSO dynamics.

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