HILO — Hawaii Island is known for its microclimates.
And they could be one reason why permafrost exists inside two craters — Pu‘u Wekiu and Pu‘u Haukea — atop Maunakea.
Norbert Schorghofer, a former University of Hawaii researcher, said that a few times a year weather conditions trap cold air inside the craters, causing temperatures to plummet.
That’s the explanation given for the lowest temperature ever record on the mountain of minus-20 degrees Celsius (minus-4 degrees Fahrenheit) inside Pu‘u Wekiu in January 2009. In comparison, temperatures rarely dip far below freezing at nearby observatories.
But even these temperature anomalies won’t be enough to save permafrost on Hawaii’s tallest mountain.
Schorghofer, who recently co-authored another study on permafrost on Maunakea and ice caves on Mauna Loa, said the amount of perennial ice on both mountains is shrinking as a result of climate change.
He estimated permafrost, detected with ground-penetrating radar, has shrunk by about 90 percent at Pu‘u Haukea since the 1970s, and he wouldn’t be surprised if the last ice at Pu‘u Wekiu, the summit crater, has disappeared since measurements were taken a few years ago.
“The bottom line is, none of these factors are enough” to stop the melting, Schorghofer said.
He estimated the larger deposit of permafrost at Pu‘u Haukea could last a few more decades.
According to UH, the ice at Pu‘u Wekiu was 11 yards thick and 27 yards long in 1969.
Permafrost at Pu‘u Haukea is now at least 55 yards wide and about 11 yards thick.
On Mauna Loa, perennial ice is found at the Mauna Loa ice cave and Arsia Cave, both on the north slope of the giant shield volcano.
Schorghofer said studying the ice helps shed light on the history of Hawaii’s climate. But the permafrost also could play a role in reducing erosion at those locations or provide a water source for insects.
“You never know what role it played,” Schorghofer said.
“We’re faced with a question now: Do we study it more or just let it melt away?
“It’s amazing there is permafrost on Maunakea to begin with.”
The research is sponsored by UH’s Office of Maunakea Management.
Email Tom Callis at tcallis@hawaiitribune-herald.com.
