Anthropogenic modification of the oceans

Author(s):  
Toby Tyrrell

Human activities are altering the ocean in many different ways. The surface ocean is warming and, as a result, it is becoming more stratified and sea level is rising. There is no clear evidence yet of a slowing in ocean circulation, although this is predicted for the future. As anthropogenic CO 2 permeates into the ocean, it is making sea water more acidic, to the detriment of surface corals and probably many other calcifiers. Once acidification reaches the deep ocean, it will become more corrosive to CaCO 3 , leading to a considerable reduction in the amount of CaCO 3 accumulating on the deep seafloor. There will be a several thousand-year-long interruption to CaCO 3 sedimentation at many points on the seafloor. A curious feedback in the ocean, carbonate compensation, makes it more likely that global warming and sea-level rise will continue for many millennia after CO 2 emissions cease.

Science ◽  
2005 ◽  
Vol 307 (5716) ◽  
pp. 1769-1772 ◽  
Author(s):  
G. A. Meehl

2014 ◽  
Vol 170 ◽  
pp. 74-85 ◽  
Author(s):  
Mireia Valle ◽  
Guillem Chust ◽  
Andrea del Campo ◽  
Mary S. Wisz ◽  
Steffen M. Olsen ◽  
...  

Author(s):  
M. A. Awal ◽  
M. A. H. Khan

Climatologically, the entire southern coastal belt of Bangladesh is most vulnerable than the other parts of the country due to its spatial geo-morphological settings. Global warming and sea level rise are already observed and predicted to be occurred more with time. These bring real negative consequences on the agricultural production and food security, and livelihood for the people live in the coastal areas. Therefore, the study was conducted to analyze the effect of global warming and sea level rise on the agriculture and food security in southern coastal areas of Bangladesh. Both primary and secondary sources of information were collected. Stakeholder consultation, direct field visits and interview of climate affected people in the coastal region were carried out for collecting information on land-use and cropping patterns and adaptation measures to be taken to boost crop production against global warming and sea level rise. By the middle and end of the twenty first century, global annual mean temperature is predicted to be increased about 1.5oC and 2.5oC, respectively. These projected warming will lead to about 14, 32 and 88 cm sea level rise by 2030, 2050 and 2100, respectively which would cause inundation of about 8, 10 and 16 percent of total land masses in Bangladesh. Most of the coastal parts and associated islands of Khulna and Barisal divisions and western part of Chattagram division lie within one meter from sea level where incursion of saline water is common. It is predicted that these areas will be inundated and unsuitable for crop production due to upcoming sea level rise. The predominant crop in entire coastal belt is transplanted Aman with sporadic occurrences of Aus rice. The land in Boro rice season either loosely occupied by mungbean, grass pea, cowpea, groundnut, soybean, potato, sweet potato, chili etc or remained fallow until the following monsoon. A systemic analysis of all of the cyclones that originated from the Bay of Bengal since 1961 indicated that most devastating cyclones formation occurred from last quarter of April through May and from middle of October to November just prior to the harvest of Boro and Aman crops, respectively. Therefore, Boro and Aman rice harvests are mostly unpredictable every year posing great threat to the food security of the coastal people. These areas are criss-crossed by innumerable water canals or channels especially in Barisal and Khulna divisions which can be utilized for Boro rice cultivation in dry season despite some levels of salinity. Cultivation of salt-tolerant crop varieties could mitigate such hindrances. Introduction of saline tolerant Boro rice in coastal cropping patterns and/or advancing the harvesting times by a fortnight in both Aman and Boro rice seasons to avert cyclonic havoc not only ensure food security but also turn the entire coastal belt into a food surplus region.


2020 ◽  
Vol 13 (10) ◽  
pp. 4925-4941
Author(s):  
Eric Larour ◽  
Lambert Caron ◽  
Mathieu Morlighem ◽  
Surendra Adhikari ◽  
Thomas Frederikse ◽  
...  

Abstract. Understanding future impacts of sea-level rise at the local level is important for mitigating its effects. In particular, quantifying the range of sea-level rise outcomes in a probabilistic way enables coastal planners to better adapt strategies, depending on cost, timing and risk tolerance. For a time horizon of 100 years, frameworks have been developed that provide such projections by relying on sea-level fingerprints where contributions from different processes are sampled at each individual time step and summed up to create probability distributions of sea-level rise for each desired location. While advantageous, this method does not readily allow for including new physics developed in forward models of each component. For example, couplings and feedbacks between ice sheets, ocean circulation and solid-Earth uplift cannot easily be represented in such frameworks. Indeed, the main impediment to inclusion of more forward model physics in probabilistic sea-level frameworks is the availability of dynamically computed sea-level fingerprints that can be directly linked to local mass changes. Here, we demonstrate such an approach within the Ice-sheet and Sea-level System Model (ISSM), where we develop a probabilistic framework that can readily be coupled to forward process models such as those for ice sheets, glacial isostatic adjustment, hydrology and ocean circulation, among others. Through large-scale uncertainty quantification, we demonstrate how this approach enables inclusion of incremental improvements in all forward models and provides fidelity to time-correlated processes. The projection system may readily process input and output quantities that are geodetically consistent with space and terrestrial measurement systems. The approach can also account for numerous improvements in our understanding of sea-level processes.


2021 ◽  
pp. 228-248
Author(s):  
Eelco J. Rohling

This chapter considers processes we cannot reverse, at least in the short term: it is already too late. These are processes related to slow responses or feedbacks in the climate system, including ocean warming and sea-level rise, and they will continue to drive change whatever we do. As explained in the chapter, ocean warming operates on timescales of centuries and resulting changes in Earth’s major ice sheets take many centuries to millennia. Sea-level rise is caused by thermal expansion due to ocean warming and by reduction in the volume of land-based ice, due to global warming. Because of the timescales involved, the oceans will keep warming for centuries, dragging global mean temperature along with them, and sea level will also rise for many centuries to come. The chapter reviews the impacts of these processes, whose inevitability means that humanity has no choice but to adapt to them.


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