Adapting to Sea-Level Rise in the Indian Ocean

2019 ◽  
pp. 75-89 ◽  
Author(s):  
Arne Harms
Keyword(s):  
Indian Ocean ◽  
Sea Level Rise ◽  
Sea Level ◽  
The Indian Ocean

scholarly journals Indian Ocean Dynamic Sea Level, Variability And Projections In CMIP6 Models

2022 ◽  
Author(s):  
Abhisek Chatterjee ◽  
Sajidh C K
Keyword(s):  
High Resolution ◽  
Indian Ocean ◽  
Sea Level Rise ◽  
Sea Level ◽  
Sea Level Variability ◽  
Regional Sea Level ◽  
The Indian Ocean ◽  
High Resolution Models ◽  
Mean State ◽  
Dynamic Sea Level

Abstract The regional sea level variability and its projection amidst the global sea level rise is one of the major concerns for coastal communities. The dynamic sea level plays a major role in the observed spatial deviations in regional sea level rise from the global mean. The present study evaluates 27 climate model simulations from the sixth phase of the coupled model intercomparison project (CMIP6) for their representation of the historical mean states, variability and future projections for the Indian Ocean. Most models reproduce the observed mean state of the dynamic sea level realistically, however consistent positive bias is evident across the latitudinal range of the Indian Ocean. The strongest sea level bias is seen along the Antarctic Circumpolar Current (ACC) regime owing to the stronger than observed south Indian Ocean westerlies and its equatorward bias. Further, this equatorward shift of the wind field resulted in stronger positive windstress curl across the southeasterly trade winds in the southern tropical basin and easterly wind bias along the equatorial waveguide. These anomalous easterly equatorial winds cause upwelling in the eastern part of the basin and keeps the thermocline shallower in the model than observed, resulted in enhanced variability for the dipole zonal mode or Indian Ocean dipole in the tropics. In the north Indian Ocean, the summer monsoon winds are weak in the model causing weaker upwelling and positive sea level bias along the western Arabian Sea. The high-resolution models compare better in simulating the sea level variability, particularly in the eddy dominated regions like the ACC regime in interannual timescale. However, these improved variabilities do not necessarily produce a better mean state likely due to the enhanced mixing driven by parametrizations set in these high-resolution models. Finally, the overall pattern of the projected dynamic sea level rise is found to be similar for the mid (SSP2-4.5) and high-end (SSP5-8.5) scenarios, except that the magnitude is higher under the high emission situation. Notably, the projected dynamic sea level change is found to be milder when only the best performing models are used compared to the full ensemble.

scholarly journals Climate-driven sea level extremes compounded by marine heatwaves in coastal Indonesia

2021 ◽  
Author(s):  
Weiqing Han ◽  
Lei Zhang ◽  
Gerald Meehl ◽  
Shoichiro Kido ◽  
Tomoki Tozuka ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Sea Level Rise ◽  
Sea Level ◽  
Tide Gauge ◽  
Surface Wind ◽  
Tide Gauge Records ◽  
Intraseasonal Oscillations ◽  
The Indian Ocean ◽  
Global Sea Level ◽  
The 1960S

Abstract The low-lying coastal and island regions are vulnerable to sea level rise and extreme events. Compounded by marine heatwaves, sea level extremes have devastating impacts on coastal community and marine ecosystems. As long tide gauge records are sparse, sea level extremes around Indonesia are poorly understood, and the Compound Height-Heat EXtreme (C-HHEX) events remain unexplored. Here we combine in situ and satellite observations with model simulations, to investigate the long-lasting (>1 month) sea level extremes and C-HHEXs along Indonesian coasts of the Indian Ocean since the 1960s. We find that 90% (80%) of the extreme sea level (C-HHEX) events, with a maximum monthly sea level anomaly of 0.45m, are clustered in an 8yr period of 2010-2017, due to anthropogenic global sea level rise and decadal enhancement driven by changing surface winds associated with a combined invigoration of the Indian and Pacific Walker Cells, atmospheric overturning circulations in east-west direction. Remote and local surface wind anomalies associated with negative phases of the Indian Ocean Dipole (IOD) - enhanced by La Niña – drive individual C-HHEX events under a precondition of shallow thermocline (a region of subsurface ocean with temperature decreases rapidly downward). By contrast, winds associated with monsoon and its intraseasonal oscillations force the sea level alone events under a deep thermocline condition. We conclude that the shoaling thermocline in eastern Indian Ocean under anthropogenic warming and global sea level rise favorably precondition the ocean for stronger and more frequent sea level extremes and C-HHEXs, increasing the environmental stress on Indonesia.

Intraseasonal-to-Interannual Variability of South Indian Ocean Sea Level and Thermocline: Remote versus Local Forcing

2012 ◽  
Vol 42 (4) ◽  
pp. 602-627 ◽  
Author(s):  
Laurie L. Trenary ◽  
Weiqing Han
Keyword(s):  
Indian Ocean ◽  
Interannual Variability ◽  
Sea Level ◽  
Time Scales ◽  
Ekman Pumping ◽  
Remote Forcing ◽  
South Indian ◽  
The Pacific ◽  
The Indian Ocean ◽  
Thermocline Variability

Abstract The relative importance of local versus remote forcing on intraseasonal-to-interannual sea level and thermocline variability of the tropical south Indian Ocean (SIO) is systematically examined by performing a suite of controlled experiments using an ocean general circulation model and a linear ocean model. Particular emphasis is placed on the thermocline ridge of the Indian Ocean (TRIO; 5°–12°S, 50°–80°E). On interannual and seasonal time scales, sea level and thermocline variability within the TRIO region is primarily forced by winds over the Indian Ocean. Interannual variability is largely caused by westward propagating Rossby waves forced by Ekman pumping velocities east of the region. Seasonally, thermocline variability over the TRIO region is induced by a combination of local Ekman pumping and Rossby waves generated by winds from the east. Adjustment of the tropical SIO at both time scales generally follows linear theory and is captured by the first two baroclinic modes. Remote forcing from the Pacific via the oceanic bridge has significant influence on seasonal and interannual thermocline variability in the east basin of the SIO and weak impact on the TRIO region. On intraseasonal time scales, strong sea level and thermocline variability is found in the southeast tropical Indian Ocean, and it primarily arises from oceanic instabilities. In the TRIO region, intraseasonal sea level is relatively weak and results from Indian Ocean wind forcing. Forcing over the Pacific is the major cause for interannual variability of the Indonesian Throughflow (ITF) transport, whereas forcing over the Indian Ocean plays a larger role in determining seasonal and intraseasonal ITF variability.

Natural decadal sea-level variability in the Indian Ocean: lessons from CMIP models

2019 ◽  
Vol 53 (9-10) ◽  
pp. 5653-5673
Author(s):  
A. G. Nidheesh ◽  
Matthieu Lengaigne ◽  
Jérôme Vialard ◽  
Takeshi Izumo ◽  
A. S. Unnikrishnan ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Sea Level ◽  
Sea Level Variability ◽  
The Indian Ocean

scholarly journals Repeated evolution of flightlessness in Dryolimnas rails (Aves: Rallidae) after extinction and recolonization on Aldabra

2019 ◽  
Vol 186 (3) ◽  
pp. 666-672 ◽  
Author(s):  
Julian P Hume ◽  
David Martill
Keyword(s):  
Indian Ocean ◽  
Sea Level ◽  
Upper Pleistocene ◽  
Fossil Evidence ◽  
Before And After ◽  
Repeated Evolution ◽  
The Indian Ocean

AbstractThe Aldabra rail, Dryolimnas cuvieri subsp. aldabranus, endemic to the Aldabra Atoll, Seychelles, is the last surviving flightless bird in the Indian Ocean. Aldabra has undergone at least one major, total inundation event during an Upper Pleistocene (Tarantian age) sea-level high-stand, resulting in the loss of all terrestrial fauna. A flightless Dryolimnas has been identified from two temporally separated Aldabran fossil localities, deposited before and after the inundation event, providing irrefutable evidence that a member of Rallidae colonized the atoll, most likely from Madagascar, and became flightless independently on each occasion. Fossil evidence presented here is unique for Rallidae and epitomizes the ability of birds from this clade to successfully colonize isolated islands and evolve flightlessness on multiple occasions.

scholarly journals A discussion concerning the floor of the northwest Indian Ocean - Preface

1966 ◽  
Vol 259 (1099) ◽  
pp. 135-136
Keyword(s):  
Indian Ocean ◽  
Sea Level ◽  
Experimental Work ◽  
Royal Society ◽  
Research Programme ◽  
Woods Hole Oceanographic Institution ◽  
International Council ◽  
The Earth ◽  
The Indian Ocean ◽  
Lengthy Discussion

Some years ago at the first and preliminary meeting of the Scientific Committee on Oceanic Research (S. C. O. R.) of the International Council of Scientific Unions (I. C. S. U.), one of the prime tasks was to seek some major international sea-going undertaking which the Committee could initiate and subsequently sponsor. This undertaking would have to interest many nations and embrace many oceanographical disciplines. The meeting took place at the Woods Hole Oceanographic Institution and it was therefore appropriate (although not improbable!) that Dr C. H. O’D. Iselin should be first to suggest that an international research programme in the Indian Ocean fulfilled both these objects. He emphasized that many nations bordered it and that there were interests in this comparatively unknown ocean for any scientist concerned with meteorology, biology (above or below sea level), the physics and chemistry of the ocean waters, or the Earth beneath the sea. He also made clear that the monsoons made the Indian Ocean unique as regards oceanic and atmospheric circulation. The meeting, after lengthy discussion, endorsed Dr Iselin’s proposal and the end results of the tremendous international effort which thereby was created are now coming in. Some of these results were delivered at a Discussion Meeting held in the rooms of the Royal Society on 12 November 1964. The papers given at this meeting, and which are published below were restricted to geological and geophysical aspects of the northwest Indian Ocean (except for the first paper concerning the physiography of the whole of the Indian Ocean). This collection of papers represents, by no means, the last word on these aspects of this area. Indeed there is much more work to be published on experimental work already completed, and for many of us the work already accomplished has produced many new problems which require further experimental work in the area

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