Sunday, December 7, 2014

UH research: Warming's dark twin, acidification, eroding reefs.

Global warming’s dark twin, ocean acidification, is disrupting life in the oceans as dangerously as warming itself.

A recent study by University of Hawai`i researcher Nyssa Silbiger and her colleagues indicates that coral reefs are eroding as increasingly acid oceans eat away at their calcium carbonate structures.

(Image: MicroCT scan of experimental blocks reveals bioerosion scars. Credit: N Silbiger, M Riccio/Cornell.)

Corals are always in dynamic tension, as the building work of coral polyps is balanced against the destructive work of parrotfish and boring marine worms. But studies at the University of Hawai`i Institute of Marine Biology shows that acidification is tipping the scales toward destruction.

The paper, Reefs shift from net accretion to net erosion along a natural environmental gradient, by Silbiger, and co-researchers Òscar Guadayol, Florence I. M. Thomas and Megan J. Donahuein, is in the journal Marine Ecology Progress Series.

Researchers placed coral blocks onto the Kane`ohe Bay reef for a year, measuring them before and after by both weight and high-resolution computed tomography (CT) scans. Different parts of the reef have different levels of acidity, current flow, temperatures and other variables.

They found that the big predictor of coral erosion was acidity of the water. And since oceans are expected to continue to acidify from carbon-dioxide loading, that’s bad news for reefs.

And particularly bad news for reef areas subject to higher levels of acidity. The study found that rather than being uniform, acidity levels vary both in place and time.

“It was surprising to discover that small-scale changes in the environment can influence ecosystem-level reef processes. We saw changes in pH on the order of meters and those small pH changes drove the patterns in reef accretion-erosion,” Silbiger said in a news release.

What does it all mean?

“Our findings suggest that increases in reef erosion, combined with expected decreases in calcification, will accelerate the shift of coral reefs to an erosion-dominated system in a high-CO2 world. 

"This shift will make reefs increasingly susceptible to storm damage and sea-level rise, threatening the maintenance of the ecosystem services that coral reefs provide,” the researchers write.

Citation: NJ Silbiger, O Guadoyal, FIM Thomas, MJ Donahue (2014) Reefs shift from net accretion to net erosion along a natural environmental gradient. Marine Ecology Progress Series, vol. 515, doi: 10.3354/meps10999

© Jan TenBruggencate 2014

Friday, December 5, 2014

Hurricanes self-feed, sucking up El Nino heat from the deep ocean

It has long been asserted that El Nino events, warming the tropical Pacific as they do, promote hurricanes—but it may not occur as we’ve previously assumed.

(Image: Hurricane tracks shown in black in the eastern and central Pacific. Credit: Jin/SOEST.)

University of Hawai`i researchers have identified a two or three-season delay that explains a lot about hurricane behavior. The El Nino hot water sinks, moves in the ocean, and then surges back to the surface to fuel tropical cyclones.

And that’s important information in terms of predicting hurricane frequency and ferocity.

Fei-Fei Jin and Julien Boucharel, both of the UH Mānoa School of Ocean and Earth Science and Technology (SOEST), published their study in the journal Nature. 

The researchers looked into the phenomenon in which El Nino is strongest in winter, but hurricane frequency picks up in the following summer and fall. At that time, most of the heated water from the El Nino is stored deep in the ocean of the eastern North Pacific.

But it may be that the activity of a young hurricane can suck that warm water to the surface, in essence finding the heat needed to fuel itself and supercharge the hurricane’s strength.

“We did not connect the discharged heat of El Niño to the fueling of hurricanes until recently, when we noticed another line of active research in the tropical cyclone community that clearly demonstrated that a strong hurricane is able to get its energy not only from the warm surface water, but also by causing warm, deep water – up to 100 meters deep – to upwell to the surface,” Jin said. He was quoted in a University of Hawai`i press release

Boucharel said that extra heat provides a lot of destructive energy.

“The Northeastern Pacific is a region normally without abundant subsurface heat. El Niño’s heat discharged into this region provides conditions to generate abnormal amount of intense hurricanes that may threaten Mexico, the southwest of the U.S. and the Hawaiian islands,” he said.

The authors wrote in the Nature paper: “we show that El Niño—the warm phase of an ENSO cycle—effectively discharges heat into the eastern North Pacific basin two to three seasons after its wintertime peak, leading to intensified TCs.”

They continue: “As a result of the time involved in ocean transport, El Niño’s equatorial subsurface ‘heat reservoir’, built up in boreal winter, appears in the eastern North Pacific several months later during peak (tropical cylone) season (boreal summer and autumn). 

"By means of this delayed ocean transport mechanism, ENSO provides an additional heat supply favourable for the formation of strong hurricanes.”

© Jan TenBruggencate 2014

Sunday, November 16, 2014

Hot acid: where our Hawaiian oceans are going

Dumping greenhouse gases into the atmosphere doesn’t just cause atmospheric warming.

It causes lots of effects, some of them catastrophic in dramatically different ways. 

But heat is a big one all by itself, and it gets not only into the atmosphere, but into the seas. The oceans are now warmer than at any time since water temperature has been recorded.

(Image: At left, ocean temperatures, showing the rise since the beginning of the industrial age n the 1800s. The vertical green stripe at right is the 2000-2013 pause. At right, yellow and red show waters that are warmer than the long-term mean. Credit: IPRC.)

This summer has seen the highest global mean sea surface temperatures recorded since their systematic measuring started. 

“The 2014 global ocean warming is mostly due to the North Pacific, which has warmed far beyond any recorded value and has shifted hurricane tracks, weakened trade winds, and produced coral bleaching in the Hawaiian Islands," said Axel Timmermann, a climate scientist with the International Pacific Research Center at the University’s Mānoa campus.

Already-warm ocean temperatures stabilized from 2000 to 2014, then began heating up further earlier this year. (The pause invigorated climate change deniers, who famously trumpeted the stabilization as proof that warming had stopped. Unfortunately, they were once again wrong.)

(Image: Hawai`i sits in a pool of warm water. This is a NOAA image showing temperature anomalies in the central Pacific as of November 13, 2014. Once again, yellow and orange represent waters warmer than the long-term normal. Credit: NOAA/NESDIS.)

A University of Hawai`i press release describes the pattern:

“Sea surface temperatures started to rise unusually quickly in the extratropical North Pacific already in January 2014. A few months later, in April and May, westerly winds pushed a huge amount of very warm water usually stored in the western Pacific along the equator to the eastern Pacific. This warm water has spread along the North American Pacific coast, releasing into the atmosphere enormous amounts of heat—heat that had been locked up in the Western tropical Pacific for nearly a decade.”

“The warm temperatures now extend in a wide swath from just north of Papua New Guinea to the Gulf of Alaska,” Timmermann said. 

And of course, warmer waters aren’t all that’s going on in the oceans. There’s sea level rise. And changes in current patterns. And shifting of nutrients that in turn affect fisheries. And lots more. Ocean acidification is still another big one.
The excess of carbon-dioxide in the atmosphere is mixing into the oceans along with the heat, and acidifying the water. That has dramatic impacts on the survival of various kinds of marine life, including coral reefs, shellfish and a lot of tiny marine animals that are basic to the oceanic food chain.

If you're interested, here is a good resources on that issue. 

© Jan TenBruggencate 2014

Monday, November 10, 2014

It only takes a few humans to kill off easy prey like moa, and maybe Hawaiian monk seals.

A new study suggests that it takes very few humans to kill off a large, easily-caught food species.

There were only about 2,500 Maori in New Zealand by the time they killed off the last of the moa—that giant bird which, along with the dodo, is emblematic of lost wildlife.

(Image: A representation of an upland moa, Megalapteryx didinus. Credit: George Edward Lodge.)

“Both the Polynesian settlement of New Zealand and moa extinction are recent enough to be dated with a high degree of precision.

“In addition, the founding human population can be estimated from genetic evidence,” says an article published in Nature Communications, by Richard Holdaway, of the Universiity of Canterbury and Palaecol Research Ltd., and his New Zealand and Australia co-authors Morten Allentoft, Christopher Jacomb, Charlotte Oskam, Nancy Beavan and Michael Bunce.

What they found was that the moa were hit by a multi-part human impact: The big, long-necked birds were killed directly, their eggs were collected, and their habitat was destroyed.

“Polynesians exterminated viable populations of moa by hunting and removal of habitat. High human population densities are not required in models of megafaunal extinction,” the authors write.

In a press release from the University of Otago, the researchers said they used radiocarbon dating from 270 sites around New Zealand.  

“Analysis of 210 of the ages showed that moa were exterminated first in the more accessible eastern lowlands of the South Island, at the end of the 14th century, just 70-80 years after the first evidence for moa consumption. Analysis of all 270 dates, on all South Island moa species from throughout the South Island, showed that moa survived for only about another 20 years after that."

The entire population of moa was gone between the first signs of human activity in South Island, which was no earlier than 1314 BC and the loss of the last moa in 1425, give or take a decade.
Is there a Hawaiian equivalent? Hawai`i had its own moa, the moa nalo, which was a giant flightless duck, and it also disappeared early. This thick-beaked species had different species on several islands, three of them in the genus Thambetochen. The massive Kaua`i version, Chelychelynechen quassus, was known as the turtle-jawed moa nalo.

They would have been a little harder to locate than the 500 pound, 12-foot New Zealand moa, but they were all extinct by the time Europeans arrived.

Additionally, the Hawaiian monk seal was killed off early in the main Hawaiian Islands--so early that its bones are only known from a very few early archaeological sites. Seals were still found in the Northwestern Hawaiian Islands, and from there they began the slow process of repopulating the main islands.
For early Hawaiians, the seals, which sun themselves and raise their pups on the beach, would have been very easy and nutritious prey.

© Jan TenBruggencate 2014

Thursday, November 6, 2014

Gov's race polling: Ward is queen...this time

Election 2014 was a critical election in the Islands, but for political junkies, a big question was: How did the pollsters do?

This year, in the governor’s race, one Hawaii-based pollster was spot-on, and the other wasn’t too far off.

The national polls, not so much.

First, these were the actual results in the governor’s race: Winner and Democrat David Ige 49 percent of the vote; Republican Duke Aiona 36.7 percent. Independent Mufi Hanneman 11.6 percent. And Libertarian Jeff Davis 1.7 percent.

Which poll had the most accurate numbers? 

That would be Becky Ward’s Ward Research, and her Star-Advertiser/Hawaii News Now Hawaii Poll, done of 605 likely voters Oct. 11 to 18.

Ward had Ige 47, Aiona 35, Hannemann 12 and Davis 1.

Civil Beat/Merriman River wasn’t far off, but significantly understated Ige’s numbers and overstated Libertarian Jeff Davis’. In this poll, of 1,221 likely voters Oct. 16 to 19.

Merriman River had Ige 40, Aiona 34, Hannemann 11 and Davis 6.

Then there were the Mainland polls, which were a little embarrassing..

CBS News/New York Times/YouGov did an online poll of 1,002 likely voters Oct. 16-23—roughly the same time period as Ward and Merriman’s polls. But they vastly overstated Ige’s vote, and vastly understated Aiona and Hanneman.

They had Ige 54, Aiona 22, Hannemann 5. They didn’t bother polling about the Libertarian Davis and wrapped him into a 19 percent undecided.

Finally, a Rasmussen poll of 750 likely voters Sept. 9-10 had the race a dead heat between Ige and Aiona. This poll was a month earlier than the others, so may not be directly comparable.

Rasmussen had Ige 40, Aiona 39, Hannemann 14 and Davis and the undecided voters at 7.

That said, and Ward herself concedes, nobody got everything right. The case in point is the race for the 1st District U.S. House race, where most polling saw a tie between Democrat Mark Takai and Republican Charles Djou.

The actual numbers: Takai 51.2 percent , Djou 47.4. 

Close, but the difference is nearly 7,000 votes.

In the polling closest to the election, Ward’s Hawai`i Poll had it a 47-47 tie, and Civil Beat/Merriman River had them tied at 45-45.

Back in August, the Washington Post ran a snarky story about the quality of polling in Hawaii. 
You gotta be careful with the snarky. It’ll come back to bite you.

On the Mainland this week, all the talk is about how national pollsters managed to miss the massive GOP win across the country. 

If Tip O`Neill was right and all politics is local, then maybe those Mainland folks ought to pay more attention to the local pollsters, who know local conditions and election trends.

© Jan TenBruggencate 2014