El Nino fading out--good news for hurricane-phobic islanders

The mild El Nino that has been in place this spring and early summer appears to be on the way out.

Statistically speaking, thatʻs good news in terms of hurricanes. The Hawaiian Islands tend to have a couple fewer hurricanes per year in periods when El Nino is not in play. 

Here is a rundown on whatʻs been going on, from NOAAʻS Climate Prediction Center. 

And here is the latest news—todayʻs assessment that the current El Nino will dissipate in the next month or so. 

This is the synopsis from todayʻs report: "A transition from El Niño to ENSO-neutral is expected in the next month or two, with ENSO-neutral most likely to continue through Northern Hemisphere fall and winter."

That doesnʻt mean weʻre out of the woods. Itʻs still hurricane season, but this suggests weʻll move statistically back to normal conditions, which is about 3.5 named storms per season in the Central Pacific.

© Jan TenBruggencate 2019

Pele slipping upslope to Mauna Loa, pumping magma, USGS raises caution level yellow

Peleʻs Kilauea home Halema`uma`u. Credit: USGS

Is Madame Pele shifting residences, slipping upslope from her Kīlauea playground to her mountain palace at Mauna Loa?

It seems that way because thatʻs where sheʻs rumbling now.

After last yearʻs dramatic destruction on Kīlaueaʻs East Rift Zone, destroying homes by the hundreds and forests by the thousands of acres, Kīlauea has been quiet. That quietness, according to the USGS Volcano Hazards Program, has now continued for some months.

What of the other Hawaiian active volcanoes?

Haleakala remains quiet, as well. Hualalai too. Mauna Kea, which hasnʻt erupted in 4,600 years, shudders now and then, but mainly remains serenely calm. Lo`ihi, the undersea volcano building off the Hawai`i Island coast, shakes occasionally, but doesnʻt appear ready to erupt.

But seismic observations indicate thereʻs new activity now under massive Mauna Loa—the biggest active volcano on the planet. Not that itʻs ready to release raw lava in the short term. But right now, it is the most active of the Hawaiian volcanoes.

Magma—the term for molten rock underground—is moving. The volcano stores magma in different places, and one of them is a fairly shallow reservoir beneath the summit. Earthquake activity around that reservoir indicates that thereʻs movement in that region.

The Hawaiian Volcano Observatory uses a range of equipment to take, as it were, Peleʻs pulse. There are seismic monitors, and tilt meters, and even satellite measurements. You can see the observatoryʻs reporting on Mauna Loa here.

So far, the geologists are using very careful language, clearly intending to inform but not alarm.

"For the past several months, earthquake and ground deformation rates at Mauna Loa Volcano have exceeded long term background levels. An eruption is not imminent and current rates are not cause for alarm. However, they do indicate changes in the shallow magma storage system at Mauna Loa," the observatory reports.

It has upped Mauna Loaʻs alert level from placid green to cautious yellow. That means thereʻs stuff going on but the experts donʻt think an eruption is imminent. For perspective, the next two levels would be orange (eruption possible in as little as two weeks) and red (eruption likely within 24 hours.)

Weʻre nowhere near those more fiery color levels, but again, thereʻs something going on. It started with a significant earthquake "swarm" in October 2018. Since then, quake level and the actual swelling and shrinking of the mountain have been above background levels.

Theyʻre not yet a big deal, but this is the kind of activity that has led to eruptions in the past.

"Seismic stations have recorded an average of at least 50 shallow, small-magnitude earthquakes per week beneath Mauna Loa's summit, upper Southwest Rift Zone, and upper west flank. This compares to a rate of fewer than 20 per week in the first half of 2018. 

Shallow earthquakes are occurring in locations similar to those that preceded Mauna Loa's most recent eruptions in 1975 and 1984," the observatory wrote.

The near-surface magma storage area seems to be inflating, filling with molten rock, they say. That said, the volcano has had similar activity twice since 2000, without an eruption...so this is not a countdown.

"As has happened before, it is possible that current low-level unrest will continue and vary in intensity for many months, or even years without an eruption. It is also possible that the current unrest is an early precursor to an eventual eruption. At this time, we cannot determine which of these possibilities is more likely," the observatory reported.

If an eruption nears, there should be plenty of warning signs: "These signs could include further increases in rates of earthquakes and ground deformation, increases in the sizes of earthquakes, an increase in surface temperatures, or an increase in visible steam plumes or sulfur dioxide emissions."

Mauna Loa erupted 33 times since 1843. That works out to once every five years, although some of those were quite small. Among larger eruptions—ones whose lava covered 10 square kilometers or more, there were 16—one every 11 years.

The last eruption was in 1984, meaning itʻs been 35 years without a Mauna Loa eruption.

Kīlauea was erupting during much of Mauna Loaʻs recent quiet period. For many years, some scientists argued that a connection between the volcanoes prevented one from erupting while another was spewing lava. You can still see this information on websites, but the 1984 double eruption proved this wrong. Hereʻs a New York Times storyon that. 

© Jan TenBruggencate 2019

Hawaiian tradewinds shifting NE to East, and that means warmer weather for us

It feels warmer in the Islands, and it is—in part because there are significant changes in our tradewind flow.

It is not that the trades have stopped blowing, but that theyʻre blowing from warmer water, which makes the breeze warmer.

State Climatologist  Pao-Shin Chu said wind data over the past 40 years show a definite shift in the flow of tradewinds. Theyʻre blowing more from the warmer waters east of us, and less from the cooler waters northeast of us.

Chu, a meteorologist at the University of Hawai`i, compared two sets of decades-long data for winds at Honolulu Airport. And while the two sets are not precisedly comparable, they both tell the same story—a shift from northeast trades to easterly trades.

What does that mean to the person on the street, or sitting in front of a fan at home, or selecting restaurants for the efficiency of their air conditioning?

"The wind from the northeast is cooler than with the easterly component," Chu said.

Chu first noted the change in a paper published in 2012 in the Journal of Geophysical Research. He has since reviewed updated numbers and said the trend continues.

That paper, by Jessica A. Garza, Chu, Chase W. Norton and Thomas A. Schroeder, is entitled "Changes of the prevailing trade winds over the islands of Hawaii and the North Pacific."  

The researchers looked at wind data from eight stations on land and from ocean buoys around the Islands. The data runs from 1973 to 2009. Here is a press release on that paper.

"The northeast trade frequency is found to decrease for all eight stations while the east trade winds are found to increase in frequency," the authors wrote.

Hawai`i gets its reputation for having a comfortable climate in part from the remarkable consistency of the trade wind flow. It is the most consistent wind field on the planet, the authors said.

When Chu recently reviewed a newer set of wind numbers, from 1980 to 2014, he found a compable result: The frequency of northeast trades drops while the frequency of easterly trades rises.

He said that at the beginning of the data set, there were 170 days of northeast trades, and they dropped to 150 by the end of the period.

Meanwhile, east trades increased from 95 to 120 days.

And there is other news in trade winds. Chinese researchers report that during the past century, trade wind speeds have increased in the western Pacific, but decreased in the eastern Pacific. (Hawai`i is kind of in the middle.)

That study "Long-term trend of the tropical Pacific trade winds under global warming and its causes," is by a team lead by Yang Li, an atmospheric scientist at Chinaʻs Chengdu University. 

University of Hawai`iʻs Chu said he has seen a slight weakening in Hawaiian tradewinds, but not enough to be statistically significant.

©Jan TenBruggencate 2019

Ancient botanical ink between far-flung Polynesian cultures, and why does Pitcairn keep showing up?

Polynesian voyagers visited nearly every island in the tropical and subtropical Pacific, and they colonized and remained on most of them.

But a remarkable few were abandoned, despite apparently having the resources to maintain a population. Pitcairn is one of those.

This remote high island in the eastern South Pacific is best known as the refuge that the Bounty mutineers and their Tahitian friends went to, to hide from the British navy. Pitcairn was uninhabited at the time. But it had been inhabited.

Canoe-sailing Polynesians had moved there a millenium ago, apparently thrived for 400 years, and then vanished. Like a sailing ship found drifting with no one aboard, its story is a mystery. Even today, as a British Overseas Territory, it has difficulty attracting people. An immigration site for Pitcairn is here. 

There is something eerie about Pitcairnʻs Polynesian history. Where did these islanders go? Did they abandon their island. Were they killed off by disease? Did war play a role? Or starvation?

One thing they may not have been is alone. 

In a major study of the Pacific-wide connections between island samples of paper mulberry (wauke, or Broussonetia papyrifera), which this blog covered in an earlier post, the plants collected on Pitcairn display deep genetic connections to Polynesiaʻs ancient past.

Wauke was a canoe plant—one of the critically important plants that all Polynesian voyaging canoes carried on their missions of colonization. It was important because it was the key plant for making fabric.

In studying the genetic differences and similiarities of wauke collected on different islands, the researchers found that Pitcairnʻs plants had strong genetic roots elsewhere in Polynesia.

For example, they found that "New Guinea is directly connected to Remote Oceania through Pitcairn."

There are distinct cultural differences between portions of Polynesia that were occupied at different times. For example, Fiji, Tonga and Futuna are an older Polynesian culture, which the authors call Western Remote Oceania (WRO). Islands like Niue, the Cook Islands, the Marquesas, the Austral Islands and Rapa Nui are understood to have been populated later. They are called Eastern Remote Oceania (ERO). New Guinea, in Near Oceania is outside that range and is considered even older in Polynesian history.

Yet, then there is Pitcairn.

"We found Pitcairn plants in a pivotal position between WRO and ERO. In addition, Pitcairn accessions linked with genotypes from New Guinea in Near Oceania," they write.

How to explain that? Pitcairn is physically in the newer area of Eastern Remote Oceania. Yet its wauke tells a different story, a story of ancient connections: "The link between these... groups was Pitcairn," the researchers write.

But the authors suggest that this does not suggest that Pitcairn was an ancient voyaging crossroads that maintained voyaging connections across thousands of miles of open sea. "We do not propose a direct migration route from New Guinea to Pitcairn," the authors write.

The explanation, they suggest, is simpler.

Pitcairn was occupied so long ago, and also abandoned so long ago, that it retained the ancient genetics of the wauke that the earliest voyagers carried with them.

"This relationship between samples from New Guinea and Pitcairn represents the survival of old genotypes on Pitcairn Island due to centuries of isolation after initial colonization by Austronesian speaking peoples. We suggest that these genotypes were probably lost on other islands that represent the intermediate steps of dispersal and migration," they write.

Hawaiʻi, the Marquesas, Rapa Nui (Easter Island) and Pitcairn are also linked genetically through wauke.

"The connections observed in our study through the genetic analysis of paper mulberry plants... show ties between Rapa Nui and Marquesas and between the Marquesas and Hawaii," the write.

Ultimately, the work confirms the conclusion that all Polynesia is connected, and that a thousand years ago, this stone age culture was tightly connected.

©Jan TenBruggencate 2019

Wauke tracks Polynesian voyaging routes: New genetic studies

Fiji kapa making. 

Credit: Andrea Seelenfreund

Genetic studies of one of the key canoe plants, wauke, appear to confirm Polynesian voyaging from west to east across the Pacific, but also identify key regions of voyaging.

Wauke, also known as paper mulberry or Broussonetia papyrifera, is the raw material for some of the best Hawaiian and Polynesian kapa or bark cloth. It also produces edible fruit. And interestingly, most of Polynesia only has female plants, while the Hawaiian Islands have both males and females.

How does that happen? The Hawaiian males apparently were brought to these islands after European contact. That will be reviewed later.  On all other Polynesian islands, all plants found today are female, but the research did find a couple of examples of male plants in samples from the early 20th century from the Marquesas and Rapa. 

This is confusing. The authors of one study on the subject said it could be that wauke males were included in early voyaging, and have since disappeared, leaving the plants to be reproduced only by human involvement. But there is an odd alternative possibility. The Broussonetia clan is known to occasionally undergo sex reversion, in which female plants may rarely produce male flowers, or males may change to females. 

Wauke

Credit: USDA, J.S. Peterson

Hawai`i is different from the rest of Polynesia because it still has male wauke. But those do not appear to be from early Polynesian introductions. Rather, the males apparently descend from a separate, non-Polynesian introduction to the Islands by 19th century Asian immigrants. The male wauke do not appear to have come through Polynesia, like the females. You can read more about the sexual distribution of the paper mulberry here. 

"Most paper mulberry plants now present in the Pacific appear to be descended from female clones introduced prehistorically," the authors of that paper write.

The dominant wauke stock in the Pacific appears to have originated in Taiwan, where, as in China and Indochina, it is native. But as a valued canoe plant, it was carried by Polynesian voyagers virtually everywhere they went. The plants are found not only in Hawai`i but at New Caledonia, Fiji, Samoa, Wallis and Tonga, in the Marquesas, the Society Islands, the Austral islands (Rapa), Pitcairn and Rapa Nui or Easter Island.

Wauke is a dioecious plant, meaning that male and female flowers occur on different plants. Because the existing plants are all female, the Polynesian wauke can't reproduce itself, and needs human help being transported and being kept alive.

"In the absence of breeding populations, the spread (i.e. movement) of paper mulberry depends entirely on a continuous human cultural tradition of preserving, propagating and transporting the plant," wrote the authors of the paper cited above.

In a new paper, many of the same authors, add to the story of the wauke. The latest paper, published this year in the journal PLOS One, is entitled "Human mediated translocation of Pacific paper mulberry [Broussonetia papyrifera (L.) L’He ´r. ex Vent. (Moraceae)]: Genetic evidence of dispersal routes in Remote Oceania."

The authors are from Chile, New Zealand and Taiwan. They include Gabriela Olivares, Barbara Peña-Ahumada, Johany Peñailillo, Claudia Payacan, Ximena Moncada, Monica Saldarriaga-Cordoba, Elizabeth Matisoo-Smith, KuoFang Chung, Daniela Seelenfreund and Andrea Seelenfreund. 

A Eurekalert press release on the study, which is simpler reading. 

The researchers conducted genetic studies on samples of wauke from 380 modern and museum samples from 33 islands across the Pacific.

They found that while all those female wauke are presumably clones of an original import, there is still some genetic diversity, and it can help understand migration patterns within the remote islands of Oceania.

"Our data detect a complex structure of three central dispersal hubs linking West Remote Oceania with East Remote Oceania. despite its vegetative propagation and short timespan since its introduction into the region by prehistoric Austronesian speaking colonists," wrote co-author Andrea Seelenfreund.

The three clusters where the wauke are most closely related to each other are: 1. Tonga and Fiji; 2. The islands of Samoa, Wallis and New Caledonia; 3. and then all of eastern Polynesia, including Hawai`i, Tahiti, the Marquesas Islands, Austral Islands and Rapa Nui.

There is evidence that Hawai`i had a more complex wauke heritage than other islands. Not counting the modern importation of male plants, it appears that traditional Polynesian strains of wauke came from both eastern Polynesia and Tonga in separate importation voyages. That adds an odd wrinkle to migration theory.

There seems to be a suggestion in the data that the wauke traveled between Taiwan and New Guinea, and from there into the rest of Polynesia. There are also suggestions that the wauke traveled on all voyaging canoes that were in the process of colonizing new areas, but after that were likely not on subsequent back-and-forth voyages.

"Crops important for survival and cultural reproduction were probably aboard all colonizing canoes, although probably not part of later inter-archipelago commercial networks or part of ritual exchanges of high valued objects, such as textiles, adzes, whale teeth, shells and other items between established settlements," the authors wrote.

© Jan TenBruggencate 2019