scholarly journals Water level changes, subsidence, and sea level rise in the Ganges–Brahmaputra–Meghna delta

2020 ◽  
Vol 117 (4) ◽  
pp. 1867-1876 ◽  
Author(s):  
Mélanie Becker ◽  
Fabrice Papa ◽  
Mikhail Karpytchev ◽  
Caroline Delebecque ◽  
Yann Krien ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Water Level ◽  
Sea Level ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Climate Mitigation ◽  
Vertical Land Motion ◽  
The Ganges ◽  
And Sea Level

Being one of the most vulnerable regions in the world, the Ganges–Brahmaputra–Meghna delta presents a major challenge for climate change adaptation of nearly 200 million inhabitants. It is often considered as a delta mostly exposed to sea-level rise and exacerbated by land subsidence, even if the local vertical land movement rates remain uncertain. Here, we reconstruct the water-level (WL) changes over 1968 to 2012, using an unprecedented set of 101 water-level gauges across the delta. Over the last 45 y, WL in the delta increased slightly faster (∼3 mm/y), than global mean sea level (∼2 mm/y). However, from 2005 onward, we observe an acceleration in the WL rise in the west of the delta. The interannual WL fluctuations are strongly modulated by El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) variability, with WL lower than average by 30 to 60 cm during co-occurrent El Niño and positive IOD events and higher-than-average WL, by 16 to 35 cm, during La Niña years. Using satellite altimetry and WL reconstructions, we estimate that the maximum expected rates of delta subsidence during 1993 to 2012 range from 1 to 7 mm/y. By 2100, even under a greenhouse gas emission mitigation scenario (Representative Concentration Pathway [RCP] 4.5), the subsidence could double the projected sea-level rise, making it reach 85 to 140 cm across the delta. This study provides a robust regional estimate of contemporary relative WL changes in the delta induced by continental freshwater dynamics, vertical land motion, and sea-level rise, giving a basis for developing climate mitigation strategies.

scholarly journals Large-Scale Mode Impacts on the Sea Level over the Red Sea and Gulf of Aden

2019 ◽  
Vol 11 (19) ◽  
pp. 2224 ◽  
Author(s):  
Kamal A. Alawad ◽  
Abdullah M. Al-Subhi ◽  
Mohammed A. Alsaafani ◽  
Turki M. Alraddadi ◽  
Monica Ionita ◽  
...  
Keyword(s):  
Sea Level ◽  
Red Sea ◽  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Southern Oscillation ◽  
Positive Phase ◽  
El Nino Southern Oscillation ◽  
Gulf Of Aden ◽  
The Impact

Falling between seasonal cycle variability and the impact of local drivers, the sea level in the Red Sea and Gulf of Aden has been given less consideration, especially with large-scale modes. With multiple decades of satellite altimetry observations combined with good spatial resolution, the time has come for diagnosis of the impact of large-scale modes on the sea level in those important semi-enclosed basins. While the annual cycle of sea level appeared as a dominant cycle using spectral analysis, the semi-annual one was also found, although much weaker. The first empirical orthogonal function mode explained, on average, about 65% of the total variance throughout the seasons, while their principal components clearly captured the strong La Niña event (1999–2001) in all seasons. The sea level showed a strong positive relation with positive phase El Niño Southern Oscillation in all seasons and a strong negative relation with East Atlantic/West Russia during winter and spring over the study period (1993–2017). We show that the unusually stronger easterly winds that are displaced north of the equator generate an upwelling area near the Sumatra coast and they drive both warm surface and deep-water masses toward the West Indian Ocean and Arabian Sea, rising sea level over the Red Sea and Gulf of Aden. This process could explain the increase of sea level in the basin during the positive phase of El Niño Southern Oscillation events.

scholarly journals Future extreme sea level seesaws in the tropical Pacific

2015 ◽  
Vol 1 (8) ◽  
pp. e1500560 ◽  
Author(s):  
Matthew J. Widlansky ◽  
Axel Timmermann ◽  
Wenju Cai
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
El Niño ◽  
El Nino ◽  
Tropical Pacific ◽  
Greenhouse Warming ◽  
Mean Sea Level ◽  
Global Mean Sea Level ◽  
Global Mean ◽  
The Tropical Pacific

Global mean sea levels are projected to gradually rise in response to greenhouse warming. However, on shorter time scales, modes of natural climate variability in the Pacific, such as the El Niño–Southern Oscillation (ENSO), can affect regional sea level variability and extremes, with considerable impacts on coastal ecosystems and island nations. How these shorter-term sea level fluctuations will change in association with a projected increase in extreme El Niño and its atmospheric variability remains unknown. Using present-generation coupled climate models forced with increasing greenhouse gas concentrations and subtracting the effect of global mean sea level rise, we find that climate change will enhance El Niño–related sea level extremes, especially in the tropical southwestern Pacific, where very low sea level events, locally known as Taimasa, are projected to double in occurrence. Additionally, and throughout the tropical Pacific, prolonged interannual sea level inundations are also found to become more likely with greenhouse warming and increased frequency of extreme La Niña events, thus exacerbating the coastal impacts of the projected global mean sea level rise.

scholarly journals The Influence of 2015-16 El Niño On the Record-Breaking Mangrove Dieback Along Northern Australia Coast

2021 ◽  
Author(s):  
S. Abhik ◽  
Pandora Hope ◽  
Harry H. Hendon ◽  
Lindsay B. Hutley ◽  
Stephanie Johnson ◽  
...  
Keyword(s):  
Sea Level ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Multiple Linear Regression Model ◽  
Enso Cycle ◽  
Northern Australia ◽  
Climate Conditions ◽  
Level Height

Abstract This study investigates the underlying climate processes behind the largest recorded mangrove dieback event along the Gulf of Carpentaria coast in northern Australia in late 2015. Capitalizing on the satellite observation-based mangrove green-fraction dataset, variation of the mangroves during recent decades are studied, including their dieback during 2015. The relationship between mangrove greenness and the climate conditions is examined using available observations and by exploring the possible role of the mega 2015-16 El Niño in altering the favorable conditions for the mangroves. The mangrove greenness is shown to be coherent with the low-frequency component of sea-level height variation related to the El Niño southern oscillation (ENSO) cycle in the equatorial Pacific. The sea-level drop associated with the 2015-16 El Niño is identified to be the crucial factor leading to the dieback event. A stronger sea-level drop occurred during austral autumn and winter, when the anomalies were more than 12% greater than the previous very strong El Niño events. The persistent drop in sea-level height occurred in the dry season of the year when sea-level was seasonally at its lowest, so potentially exposed the mangroves to unprecedented hostile conditions. The influence of other key climate factors is also discussed, and a multiple linear regression model is developed to understand the combined role of the important climate variables on the mangrove greenness variation.

scholarly journals Evolutions of sea level high and warm pool in the southeastern Arabian Sea and their association with Asian monsoons : A study on cause-and-effect relationships

MAUSAM ◽  
2021 ◽  
Vol 59 (1) ◽  
pp. 87-94
Author(s):  
O. P. SINGH
Keyword(s):  
Sea Level ◽  
Summer Monsoon ◽  
El Niño ◽  
Arabian Sea ◽  
El Nino ◽  
Southern Oscillation ◽  
Monsoon Season ◽  
Warm Pool ◽  
Sea Surface ◽  
Southeastern Arabian Sea

The present study aims at gaining more insight into the evolution of warm pool and associated sea level dome in the southeastern Arabian Sea before the summer monsoon onset.  The results show that the Sea Surface Temperature (SST) maximum in the warm pool region is found during April close to the southwest coast of India.  The Sea Surface Height (SSH) maximum over the same region is observed during December. The collapse of sea level dome begins well in advance during the pre-monsoon whereas the warm pool collapses after the onset of summer monsoon during June.  Therefore, there is a lag of about three to four months between the collapses of the sea level high and the warm pool.  Most interesting aspect is the dramatic increase of SST from September and SSH from October which is continued throughout the post monsoon season (October - December). Therefore, both the collapse and evolution of warm pool are dramatic events before and after the summer monsoon.                    There are considerable variations in the intensity of warm pool and the height of sea level dome on interannual scale.  The variation during El-Nino Southern Oscillation (ENSO) epoch of 1987-88 has revealed many interesting features.  During El-Nino year 1987 the warm pool intensity reached its peak in June whereas during La Nina year 1988 the warm pool attained its maximum intensity much earlier, i.e., in April. 

Developing future sea level services for Small Island Developing States

2020 ◽  
Author(s):  
Svetlana Jevrejeva ◽  
Judith Wolf ◽  
Andy Matthews ◽  
Joanne Williams ◽  
David Byrne ◽  
...  
Keyword(s):  
Climate Change ◽  
Sea Level Rise ◽  
Water Level ◽  
Sea Level ◽  
Future Climate Change ◽  
Small Island ◽  
Caribbean Region ◽  
Caribbean Islands ◽  
The Caribbean ◽  
And Sea Level

<p>The Caribbean islands encompass some of the most vulnerable coastlines in terms of sea level rise, exposure to tropical cyclones, changes in waves and storm surges. Climate in the Caribbean is already changing and sea level rise impacts are already being felt. Considerable local and regional variations in the rate, magnitude, and direction of sea-level change can be expected as a result of thermal expansion, tectonic movements, and changes in ocean circulation. Governments in the Caribbean recognise that climate change and sea level rise are serious threats to the sustainable development and economic growth of the Caribbean islands and urgent actions are required to increase the resilience and make decisions about how to adapt to future climate change (Caribbean Marine Climate Change Report Card 2017; IPCC 2014).</p><p>As part of the UK Commonwealth Marine Economies (CME) Programme and through collaboration with local stakeholders in St Vincent, we have identified particular areas at risk from changing water level and wave conditions. The Caribbean Sea, particularly the Lesser Antilles, suffers from limited observational data due to a lack of coastal monitoring, making numerical models even more important to fill this gap. The current projects brings together improved access to tide gauge observations, as well as global, regional and local water level and wave modelling to provide useful tools for coastal planners.</p><p>We present our initial design of a coastal data hub with sea level information for stakeholder access in St. Vincent and Grenadines, Grenada and St Lucia, with potential development of the hub for the Caribbean region. The work presented here is a contribution to the wide range of ongoing activities under the Commonwealth Marine Economies (CME) Programme in the Caribbean, falling within the work package “Development of a coastal data hub for stakeholder access in the Caribbean region”, under the NOC led projects “Climate Change Impact Assessment: Ocean Modelling and Monitoring for the Caribbean CME states”.</p>

scholarly journals El Niño, La Niña, and the global sea level budget

Ocean Science ◽  
2016 ◽  
Vol 12 (6) ◽  
pp. 1165-1177 ◽  
Author(s):  
Christopher G. Piecuch ◽  
Katherine J. Quinn
Keyword(s):  
Sea Level ◽  
El Niño ◽  
Hydrological Cycle ◽  
El Nino ◽  
Southern Oscillation ◽  
Heat Content ◽  
Global Ocean ◽  
Surface Warming ◽  
Enso Events ◽  
The Pacific

Abstract. Previous studies show that nonseasonal variations in global-mean sea level (GMSL) are significantly correlated with El Niño–Southern Oscillation (ENSO). However, it has remained unclear to what extent these ENSO-related GMSL fluctuations correspond to steric (i.e., density) or barystatic (mass) effects. Here we diagnose the GMSL budget for ENSO events observationally using data from profiling floats, satellite gravimetry, and radar altimetry during 2005–2015. Steric and barystatic effects make comparable contributions to the GMSL budget during ENSO, in contrast to previous interpretations based largely on hydrological models, which emphasize the barystatic component. The steric contributions reflect changes in global ocean heat content, centered on the Pacific. Distributions of ocean heat storage in the Pacific arise from a mix of diabatic and adiabatic effects. Results have implications for understanding the surface warming slowdown and demonstrate the usefulness of the Global Ocean Observing System for constraining Earth's hydrological cycle and radiation imbalance.

Variations of Sea Level and Tidal Behaviour during El Nino/La Nina: An Example of Malaysian Coastline

2015 ◽  
Vol 73 (5) ◽  
Author(s):  
Mohd Hilmi Abdullah ◽  
Mohd Razali Mahmud ◽  
Nor Ainah Amat
Keyword(s):  
Sea Level ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Enso Event ◽  
La Niña ◽  
Observation Data ◽  
Northeast Monsoon ◽  
Tidal Variation ◽  
La Nina

The El Nino/La Nina Southern Oscillation (ENSO) phenomenon indirectly provides dramatic changes to tidal that can cause floods, drought and affect various marine activities. Tidal observation data plays important role in determining the characteristic or behaviour of tide along the coastal area especially during sudden climate change such as the phenomenon of El Nino/La Nina, the Northeast Monsoon, Northwest Monsoon and Tsunami. It is important to study the occurrence of the ENSO event and it characteristic so that it can be used for prediction and monitoring the land and water ecosystem. This research is to identify the variations of sea level and tidal behaviour in Malaysian coastline during El Nino/La Nina. The tidal observation data, meteorology data (temperature and mean sea level pressure), and Southern Oscillation Index (SOI) calculation are used to look on the changes of the tidal variation during the ENSO phenomenon. The results of this research will specially benefit in the determination of tidal level in Malaysia and to the professionals who have responsibilities in policy making, agriculture, environmental planning, economics and marine engineering.

scholarly journals Relationships between Extratropical Sea Level Pressure Variations and the Central Pacific and Eastern Pacific Types of ENSO

2011 ◽  
Vol 24 (3) ◽  
pp. 708-720 ◽  
Author(s):  
Jin-Yi Yu ◽  
Seon Tae Kim
Keyword(s):  
Sea Level ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Nodal Point ◽  
Eastern Pacific ◽  
Central Pacific ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Sst Anomalies

Abstract This study examines the linkages between leading patterns of interannual sea level pressure (SLP) variability over the extratropical Pacific (20°–60°N) and the eastern Pacific (EP) and central Pacific (CP) types of El Niño–Southern Oscillation (ENSO). The first empirical orthogonal function (EOF) mode of the extratropical SLP anomalies represents variations of the Aleutian low, and the second EOF mode represents the North Pacific Oscillation (NPO) and is characterized by a meridional SLP anomaly dipole with a nodal point near 50°N. It is shown that a fraction of the first SLP mode can be excited by both the EP and CP types of ENSO. The SLP response to the EP type is stronger and more immediate. The tropical–extratropical teleconnection appears to act more slowly for the CP ENSO. During the decay phase of EP events, the associated extratropical SLP anomalies shift from the first SLP mode to the second SLP mode. As the second SLP mode grows, subtropical SST anomalies are induced beneath via surface heat flux anomalies. The SST anomalies persist after the peak in strength of the second SLP mode, likely because of the seasonal footprinting mechanism, and lead to the development of the CP type of ENSO. This study shows that the CP ENSO is an extratropically excited mode of tropical Pacific variability and also suggests that the decay of an EP type of ENSO can lead to the onset of a CP type of ENSO with the aid of the NPO. This extratropical linking mechanism appears to be at work during the 1972, 1982, and 1997 strong El Niño events, which were all EP events and were all followed by strong CP La Niña events after the NPO was excited in the extratropics. This study concludes that extratropical SLP variations play an important role in exciting the CP type of ENSO and in linking the transitions from the EP to CP events.

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