Archive for April, 2011

Beyond ocean acidification

Research into the biological threat of reduced ocean pH has yielded many insights over the past decade. Further progress requires a better understanding of how the interplay between ocean acidification and other anthropogenic stresses impacts marine biota.

The terminology used to describe the environmental impact of rising greenhouse gas levels has evolved over the past 20 yr. The shift from ‘global warming’ to ‘climate change’, and lately to ‘planetary boundaries’, reflects a growing awareness of the multifaceted effects of anthropogenic stressors on the Earth system.

The oceans have absorbed around half of the carbon dioxide released into the atmosphere as a result of fossil fuel combustion and cement production over the past 200 yr. As a result, carbonic acid levels have risen and sea water has become increasingly acidic; pH has dropped by approximately 0.1 units since pre-industrial times, which amounts to a considerable increase in acidity. However, it wasn’t until the year 2000, and the publication of a seminal study that revealed the detrimental impact of reduced ocean pH on a group of planktonic calcifiers known as coccolithophores, that research into ocean acidification really took off. Since that time, the topic of ocean acidification has matured into a multidisciplinary field — incorporating carbonate chemistry, biology, mathematical modelling and oceanography— and has received extensive general interest, ranging from national science academies to schools.

Here, I argue that the sustained focus of the research into this growing hazard to ocean health, buoyed by its successful and widespread communication, may have obscured some of the complexity inherent in global environmental change. To redress the balance, research into the interplay between ocean acidification and numerous anthropogenic stressors, and their cumulative impact on ocean biota, is needed.
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Linking groundwater discharge to severe estuarine acidification during a flood in a modified wetland

Periodic acidification of waterways adjacent to coastal acid sulfate soils (CASS) is a significant land and water management issue in the subtropics. In this study, we use 5-months of continuous radon (222Rn, a natural groundwater tracer) observations to link estuarine acidification to groundwater discharge in an Australian CASS catchment (Tuckean Swamp). The radon time series began in the dry season, when radon activities were low (2−3 dpm L−1), and the pH of surface water was 6.4. We captured a major rain event (213 mm on 2 March 2010) that flooded the catchment. An immediate drop in pH during the flood may be attributed to surface water interactions with soil products. During the post-flood stage, increased radon activities (up to 19.3 dpm L−1) and floodplain groundwater discharge rates (up to 2.01 m3 s−1, equivalent to 19% of total runoff) coincided with low pH (3.77). Another spike in radon activities (13.2 dpm L−1) coincided with the lowest recorded surface water pH (3.62) after 72 mm of rain between 17 and 20 April 2010. About 80% of catchment acid exports occurred when the estuary was dominated by groundwater discharging from highly permeable CASS during the flood recession.
Continue reading ‘Linking groundwater discharge to severe estuarine acidification during a flood in a modified wetland’

Rising Arctic Ocean temperatures cause gas hydrate destabilization and ocean acidification

Vast amounts of methane hydrates are potentially stored in sediments along the continental margins, owing their stability to low temperature – high pressure conditions. Global warming could destabilize these hydrates and cause a release of methane (CH 4) into the water column and possibly the atmosphere. Since the Arctic has and will be warmed considerably, Arctic bottom water temperatures and their future evolution projected by a climate model were analyzed. The resulting warming is spatially inhomogeneous, with the strongest impact on shallow regions affected by Atlantic inflow. Within the next 100 years, the warming affects 25% of shallow and mid-depth regions containing methane hydrates. Release of methane from melting hydrates in these areas could enhance ocean acidification and oxygen depletion in the water column. The impact of methane release on global warming, however, would not be significant within the considered time span.
Continue reading ‘Rising Arctic Ocean temperatures cause gas hydrate destabilization and ocean acidification’

Changes in dimethyl sulfide oceanic distribution due to climate change

Dimethyl sulfide (DMS) is one of the major precursors for aerosols and cloud condensation nuclei in the marine boundary layer over much of the remote ocean. Here we report on coupled climate simulations with a state-of-the-art global ocean biogeochemical model for DMS distribution and fluxes using present-day and future atmospheric CO 2 concentrations. We find changes in zonal averaged DMS flux to the atmosphere of over 150% in the Southern Ocean. This is due to concurrent sea ice changes and ocean ecosystem composition shifts caused by changes in temperature, mixing, nutrient, and light regimes. The largest changes occur in a region already sensitive to climate change, so any resultant local CLAW/Gaia feedback of DMS on clouds, and thus radiative forcing, will be particularly important. A comparison of these results to prior studies shows that increasing model complexity is associated with reduced DMS emissions at the equator and increased emissions at high latitudes.
Continue reading ‘Changes in dimethyl sulfide oceanic distribution due to climate change’

Projected changes to growth and mortality of Hawaiian corals over the next 100 years

Background

Recent reviews suggest that the warming and acidification of ocean surface waters predicated by most accepted climate projections will lead to mass mortality and declining calcification rates of reef-building corals. This study investigates the use of modeling techniques to quantitatively examine rates of coral cover change due to these effects.

Methodology/Principal Findings

Broad-scale probabilities of change in shallow-water scleractinian coral cover in the Hawaiian Archipelago for years 2000–2099 A.D. were calculated assuming a single middle-of-the-road greenhouse gas emissions scenario. These projections were based on ensemble calculations of a growth and mortality model that used sea surface temperature (SST), atmospheric carbon dioxide (CO2), observed coral growth (calcification) rates, and observed mortality linked to mass coral bleaching episodes as inputs. SST and CO2 predictions were derived from the World Climate Research Programme (WCRP) multi-model dataset, statistically downscaled with historical data.

Conclusions/Significance

The model calculations illustrate a practical approach to systematic evaluation of climate change effects on corals, and also show the effect of uncertainties in current climate predictions and in coral adaptation capabilities on estimated changes in coral cover. Despite these large uncertainties, this analysis quantitatively illustrates that a large decline in coral cover is highly likely in the 21st Century, but that there are significant spatial and temporal variances in outcomes, even under a single climate change scenario.

Continue reading ‘Projected changes to growth and mortality of Hawaiian corals over the next 100 years’

New NIWA post-doc studies ocean acidification

A new post doctoral fellow at NIWA – Dr Claire Guy – is investigating the ecological impacts of ocean acidification on key Antarctic shellfish.

Ocean acidification is one of the pressing threats to the world’s oceans. It’s expected to affect the cold waters of the Antarctic decades before the rest of the world. But just what this threat might mean is largely unknown.

Ocean acidification has the potential to affect the basic life functions of key species, such as shellfish, and change ecosystems. Claire’s aim is to develop ecologically relevant models of consequences to key shellfish species and their wider ecosystems.

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“CO2 Toolkit” curriculum project announcement

CO2 Toolkit Curriculum Project
June 2011; May 2012
UGA Campus
Athens, GA

CALLING ALL MIDDLE AND HIGH SCHOOL EDUCATORS in the Athens- Clarke County area!

COSEE SE will be hosting a multi facetted curriculum development opportunity geared at middle and high school educators focusing on carbon dioxide and ocean acidification. This one year project, the CO2 Toolkit Curriculum Project, will consist of web meetings, a 3 day non residential workshop based in Athens, GA from June 28-30, 2011, lab time with UGA professor and scientist, Dr Brian Hopkinson, to test and try out your activities/curriculum, and the opportunity for you to take this curriculum to your students and provide feedback on your experience. Space is limited to 3 educators.   

Participants completing all requirements will receive $500 stipend, monies for activity supplies, and travel in addition to access to resources from UGA and COSEE SE for support in their curriculum development efforts throughout this year long project.  Deadline to apply is May 6th, 2011!

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How do we observe climate change?

Climate change results in a warmer Earth

The Earth is getting warmer and higher temperatures mean big changes for all ecosystems, and particularly coral reefs. Temperatures are rising because heat-trapping gases are increasing in the Earth’s atmosphere. At normal ranges, these gases (called greenhouse gases), usually keep the earth at a comfortable temperature. However, over the past 150 years, humans have been adding more and more greenhouse gases, such as carbon dioxide to the atmosphere. This trend makes the land and ocean warmer, alters weather patterns, and changes the chemistry of the oceans. These effects are known as climate change.

At any time, we can go outside and observe the weather, but climate cannot be observed in one day or even one year because climate is the long-term weather conditions in a region. However, long-term monitoring programs, such as the one conducted by the Pacific Island Network help us observe the impacts of climate change in the Mid-Pacific.

Be a Web Ranger and investigate the global connections of climate change.
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“Your Changing Ocean” workshop

FREE and Fun Behind the Scenes Lab Tour and Hands-On Activities

Wednesday, May 4th, 2011
6:00 – 8:00 PM
Marine Science Institute Auditorium
UC Santa Barbara

Global Warming. Climate Change. Dead Zones. Ocean Acidification. These topics appear in the news regularly but what do they REALLY mean? Join us for a night of understanding Your Changing Ocean. During this special behind-the-scenes tour of Dr. Gretchen Hofmann’s lab, you will learn about current research, observe local marine life, and participate in hands-on activities that demonstrate what ocean change means for life in the ocean, fisheries and YOU. Space is limited; please register before April 27th at: YourChangingOcean@gmail.com
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Ocean acidification documentary in Icelandic (video)


Interview with Jon Olafson and documentary on ocean acidification in Icelandic.
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