Oceans on an acid trip are cause for concern

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As island residents, our lives are intimately intertwined with the ocean, in more ways than just having a good day at the beach. And, those of us who live on the Big Island are close observers of the volcanic activity in our backyards. So we should be particularly interested in the role that both oceans and volcanoes play in the unfolding story of greenhouse gases and climate change.

Oceans on an acid trip are cause for concern...

Oceans on an acid trip are cause for concern

(Public domain.)

As is widely known, volcanoes emit large amounts of CO2, the most prevalent greenhouse gas in the Earth's atmosphere. A small number of individuals remain unconvinced that human activities are the major contributors to global warming, and they often direct the blame at the world's volcanoes. The total CO2 emitted from all of earth's volcanoes (approximately 200 million tons per year), however, is less than 1 percent of the CO2 released by human activities. On an annual basis, Kīlauea Volcano produces less CO2 than the city of Honolulu.

In contrast, the Earth's oceans are the largest natural reservoir for CO2. Since the beginning of the industrial revolution about 200 years ago, the sea has absorbed about 130 billion tons of carbon, nearly half of the fossil fuel carbon emissions released during this period. The oceans' uptake of excess CO2 generated by humans is starting to take a toll on the chemistry of seawater. When carbon dioxide is absorbed, it reacts with seawater to form carbonic acid. This lowers the pH of the oceans, a phenomenon referred to as ocean acidification.

The pH scale is a measure of acidity and ranges from 1 to 14. A pH of 7 is neutral. Values higher on the scale are more "basic," and those lower, more "acidic." Therefore, a decrease in pH is associated with an increase in acidity. The pH of seawater is currently around 8.05, compared with the value of 8.16 measured about 200 years ago. Like the Richter scale for earthquakes, the pH scale is logarithmic, so a change of one pH unit represents a 10-fold change in acidity. This pH is probably lower than it has been for hundreds of millennia and is changing at a rate 100 times greater than at any other time over these millennia.

The drop in seawater pH wreaks havoc with the chemical equilibrium of calcium carbonate, a mineral that is used by marine organisms, like corals, lobsters, and clams, for building shells and skeletons. As the oceans become more acidic, these organisms will grow more slowly, and corals may be unable to build reefs fast enough to outpace the erosional processes wearing them away. The impacts are likely to propagate throughout the marine food chain, affecting species diversity, commercial fisheries, and tourist economies. There are natural processes that stabilize the pH of the ocean. For instance, the deposit of the basic mineral calcium carbonate onto the sea floor from dead and decaying organisms is balanced by the introduction of fresh calcium and carbonate ions into the ocean from the weathering of rocks on the land. But these processes occur over a time scale of tens of thousands of years, rather than hundreds of years. With the current rate of CO2 increase in the atmosphere, these mechanisms for compensation won't be able to keep up.

Ocean acidification is a straightforward chemical response to increasing atmospheric concentrations of CO2 and is predicted with a high degree of certainty. While the biological consequences of ocean acidification are not yet well understood, initial information indicates that there is cause for concern for the long-term health of our oceans. Of course, other indicators of climate change, such as sea-level rise, are also of concern to us as island residents.

The average American produces about 22 tons of CO2 annually, more than 6 times the amount of the average person living outside the U.S. Modifying our habits to curb CO2 emissions can slow the rate of change for critical ocean ecosystems. For practical information on lowering your carbon footprint, go to https://www.epa.gov/energy and click on the GHG (greenhouse gas) emissions calculator.

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Volcano Activity Update

This past week, activity levels at the summit of Kīlauea Volcano have remained at background levels. The summit caldera has been expanding, indicating inflation, since the beginning of 2007. The number of earthquakes located in the summit area is at low levels (usually fewer than 10 per day are large enough to locate). A few more than the usual number of earthquakes has been occurring at shallow depths beneath the summit area and at intermediate depths beneath the south flank.

Eruptive activity at Pu`u `O`o continues. On clear nights, glow is visible from several vents within the crater. Lava is fed through the PKK lava tube from its source on the southwest flank of Pu`u `O`o to the ocean. About 1 km south of Pu`u `O`o, the Campout flow branches off from the PKK tube. The PKK tube appears to no longer be active below the top of Pulama pali, but is feeding a persistent breakout that is often visible after dark, streaming down the face of the pali to the west of the Campout Flow. The Campout tube, on the other hand, is the source for the dominant ocean entry at Kamokuna, as well as for lava sporadically entering the ocean at East Lae`apuki. Both ocean entries are located inside Hawai`i Volcanoes National Park.

In the last week, intermittent breakouts from the Campout tube, in addition to the PKK tube, have been seen on the slope of Pulama pali and on the coastal plain. A branch of the Campout tube below the pali continues to host minor surface flows inland from the sea cliff at East Lae`apuki and on the lava delta below.

Access to the sea cliff near the ocean entries is closed, due to significant hazards. The surrounding area, however, is open. If you visit the eruption site, check with the rangers for current updates, and remember to carry lots of water when venturing out onto the flow field.

Six earthquakes beneath Hawai`i Island were reported felt within the past week. A magnitude-2.7 earthquake occurred at 8:45 a.m. H.s.t. on Friday, March 23, and was located 4 km (2 miles) southwest of `O`okala at a depth of 11 km (7 miles). A magnitude-3.1 earthquake occurred at 10:37 a.m. and was located 4 km southeast of Kīlauea summit at a depth of 3 km (2 miles). Another magnitude-3.1 earthquake occurred at 9:12 a.m. on Saturday, March 24, and was located 13 km (8 miles) northeast of Pahala at a depth of 42 km (26 miles). A magnitude-2.6 earthquake occurred at 10:49 p.m. and was located 11 km (7 miles) east of Mauna Kea summit at a depth of 22 km (14 miles). A magnitude 2.0 earthquake occurred at 6:01 p.m. on Sunday, March 25, and was located 9 km (6 miles) southeast of Waimea at a depth of 15 km (9 miles). A magnitude-2.4 earthquake occurred at 7:44 a.m. on Monday, March 26, and was located 8 km (5 miles) northeast of Captain Cook at a depth of 11 km (7 miles).

Mauna Loa is not erupting. No earthquakes were located beneath the volcano. Extension of distances between locations spanning the summit, indicating inflation, continues at slow rates.