Posts Tagged 'climate'

Effects of upwelling increase on ocean acidification in the California and Canary Current Systems

Upwelling-favorable winds have increased in several coastal upwelling systems, and may further increase in the future. The present study investigates the effects of upwelling intensification on ocean acidification in the California and Canary Current Systems (CSs). Model simulations show that the volume of water undersaturated with respect to aragonite almost triples in the California CS under a doubling of wind stress. In contrast, the same wind perturbation results in the disappearance of undersaturation in the Canary CS. These contrasting responses arise from the differences in the relative contributions of circulation and biological processes to aragonite undersaturation in the two systems and the sensitivity of these processes to upwelling intensification. When combined with rising atmospheric CO 2 and increased stratification, upwelling intensification accentuates acidification in the California CS and dampens it in the Canary CS. These findings highlight the challenge to predict the future evolution of ocean acidification in regions subject to concurrent disturbances.

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Ensuring survival: oceans, climate and security

The oceans play a vital role in the global carbon cycle, regulate climate and temperature, provide food security and support the livelihoods of billions of people around the globe, especially in coastal areas (where over half the global population resides) and in small island states, where some of the most vulnerable populations rely on marine resources. However, the provision of these life-sustaining services is at risk—climate change and ocean acidification are already affecting marine ecosystems and coastal populations, threatening the ability of the oceans to continue providing economic resources and environmental services on which we so critically depend. Citing evidence of these key points, this paper calls for improved governance, the use of ecosystem-based approaches in coastal and ocean management, and urgency in transition to a low-carbon economy. With enhanced governance frameworks and a reliance on science and best practices, we can improve food security, enhance ecosystem resilience, secure sustainable livelihoods, and provide man-made and, perhaps more importantly, natural protections to threats to human health and environmental security from rising seas, acidifying oceans, coastal hazards and extreme weather events. The oceans play a vital role in combating climate change impacts, which, as much current evidence shows, will be more extensive and disastrous than previously forecast by international experts. It is urgent that the international community concertedly and decisively act to protect this function, including with the improvement of climate change cost estimates and development of financing mechanisms. We must act to increase resilience of key ocean and coastal ecosystems that provide shoreline and infrastructure protection, water quality maintenance, food security, and livelihood support. In effect, we must act to protect our own security through “ocean security”.

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Tropical cyclones cause CaCO3 undersaturation of coral reef seawater in a high-CO2 world

Ocean acidification is the global decline in seawater pH and calcium carbonate (CaCO3) saturation state (Ω) due to the uptake of anthropogenic CO2 by the world’s oceans. Acidification impairs CaCO3 shell and skeleton construction by marine organisms. Coral reefs are particularly vulnerable, as they are constructed by the CaCO3 skeletons of corals and other calcifiers. We understand relatively little about how coral reefs will respond to ocean acidification in combination with other disturbances, such as tropical cyclones. Seawater carbonate chemistry data collected from two reefs in the Florida Keys before, during, and after Tropical Storm Isaac provide the most thorough data to-date on how tropical cyclones affect the seawater CO2-system of coral reefs. Tropical Storm Isaac caused both an immediate and prolonged decline in seawater pH. Aragonite saturation state was depressed by 1.0 for a full week after the storm impact. Based on current ‘business-as-usual’ CO2 emissions scenarios, we show that tropical cyclones with high rainfall and runoff can cause periods of undersaturation (Ω < 1.0) for high-Mg calcite and aragonite mineral phases at acidification levels before the end of this century. Week-long periods of undersaturation occur for 18 mol% high-Mg calcite after storms by the end of the century. In a high-CO2 world, CaCO3 undersaturation of coral reef seawater will occur as a result of even modest tropical cyclones. The expected increase in the strength, frequency, and rainfall of the most severe tropical cyclones with climate change in combination with ocean acidification will negatively impact the structural persistence of coral reefs over this century.

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Ocean acidification in the IPCC AR5 WG II

OUP book