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Tracking climate change on Mauna Kea

Kaulana ‘o Hilo Hanakahi
Famous is Hilo, land of Hanakahi

Kuahiwi nani o Mauna-kea
For the lovely mountain of Mauna Kea,

Kuahiwi kau e ka ‘ohu
A mountain, crowned by mists

‘Ohu’ohu puakea ‘ili.
Whose summit is ever shrouded in whiteness

This song, written by Lena Machado, reflects a traditional and beloved vision of Mauna Kea. Many travelers in the 1800's reported that Mauna Kea was said to have a year round cap of snow, "perpetual winter looking down upon summer."

Three or four times in the past century there have been major snowfalls that covered the island of Hawai‘i's three highest mountains, Mauna Kea, Mauna Loa and Hualalai, down to the 7,000-foot elevation.

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1920
The snow patches became more numerous and we were obliged to ride our horses across them. At first they objected, but, after a little sniffling at the snow and some urgent coaching, they traveled willingly across the hard frozen surfaces, and continued instinctively to follow the snow rather than the rough pebble path.

The snow became deeper as we progressed, and at times the horses waded through the drifts up to their bellies. These were thrilling times, as the steeds grunted and bucked through, and the powdery snow was scattered in all directions.

Real Winter in the Tropics
by Merlyn D. L. Forbes
Paradise Of The Pacific
May, 1922

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1930
"Snow, what do you mean snow?" they ask. And Eben Low, who several years ago was Hawaii's most famous cowboy, and who now has given up the range to follow the more prosaic life of a business man, will tell them what he means.

"Snow, fifteen feet of it, and lakes covered with a foot and a half of solid ice, and temperature below freezing," he will tell you. And what's more he can produce albums of pictures to prove it.

The snow is deeper on Mauna Kea and Mauna Loa in January, February, and March than in any other months, but Mr. Low recalls having seen patches of snow on the mountains in August. Mr. Low, who spent many years ranching on the Big Island, tells stories of crossing Lake Waiau on horseback in the winter months when the lake was frozen over, of snow fifteen feet deep, of icy blizzards, and fireplaces where fires were kept burning all day.

In Mr. Low's album, which by the way, tells a fascinating story of ranching in the old days in Hawai‘i, are pictures that might have been taken in the snow fields of the northwest or in Alaska. Most of them were taken some twenty years ago when Mr. Low was a cowboy on the Parker ranch, the Woods ranch, his own ranch, and at the time he was manager of the Humuula Sheep station on Hawaii.

Semi-Tropic Snow
by Allan Grant
Paradise of the Pacific
December 1930

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1937
Above 10,000 feet, snow falls generally during the period October-May and in some years, every month. The repeated snows during the colder seasons may form a thick continuous white cap that remains for several months. During a snow storm in February, 1936, generally regarded as the most severe storm in at least 25 years, the lower limit of snow which remained on the ground around the slopes of Mauna Kea followed approximately the 7,000 foot contour line.

General Features and Glacial Geology of Mauna Kea, Hawaii
by Herbert Gregory and Chester Wentworth
Bulletin of the Geological Society of America
Vol. 48, 1937

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Mauna Kea during the ice ages

Between 6,000 and 2,500,000 years ago the world-wide temperature dropped and sheets of ice thousands of feet thick covered 6,000,000 square miles of the world's continents in what is known as the ice ages. Even sub-tropical Hawai’i, lying within 20 degrees of the equator, did not escape.

Mauna Kea was one of the few places in the tropics that was repeatedly covered by glaciers during the ice ages and is considered the world's best example of a glaciated oceanic tropical volcano. A Pleistocene era ice cap as much as 350 feet thick once covered about twenty-eight square miles of the summit area, one “lobe” dipping to as low as the 10,500-foot elevation. The last glacier on Mauna Kea completely covered the Mauna Kea summit area with ice from about 40,000 to 10,000 years ago.

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The world-wide decrease of land temperatures during the Pleistocene period was accompanied by a lower temperature of sea water. Winds and currents changed. In time, the environment for the plants and animals changed. If there were plants on the summit of Mauna Kea, they were probably destroyed by the glaciers.

For the plants and animals of the sea, who are even more sensitive to temperature changes, the glacial climate was of profound significance. In particular, the shift from warm to cool climate and back again to warm climate is recorded in the coral reefs.

Hawaiian waters are only three degrees above the lowest limit that coral will grow. Reefs stopped growing when sea temperatures dropped three to ten degrees.

More sea water was taken up into the polar ice packs and continental glaciers, resulting in a drop in sea levels of 300 feet. After the ice cap melted on Mauna Kea and the rest of the world, the sea level of Hawai‘i rose about 300 feet.

General Features and Glacial Geology of Mauna Kea, Hawaii
by Herbert Gregory and Chester Wentworth
Bulletin of the Geological Society of America
Vol. 48, 1937

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The story of Kukahau’ula and Poli’ahu suggests a Hawaiian understanding of the history of glaciation on the mountain.

In the story, Kukahau’ula — Ku, a deity representing the male force in the form of the rising sun — pursues Poli’ahu, the snow goddess of Mauna Kea, but is constantly thwarted by frost, snow and freezing rain — a period of time that could perhaps represent the ice ages. When Kukahau‘ula finally embraces Poli‘ahu, her heart melts, the ice age is over, and the resulting snow melt forms the springs and streams that water the land below, providing life to the people.

The effects of the last ice age are still felt on the mountain. The centers of the summit cones on Mauna Kea are permanently frozen to just a few feet below the surface. This layer of permafrost, or ground ice, is all that is left of a once-giant glacier.

It wouldn't require much of a change in weather to cause a glacier on Mauna Kea again.

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The conditions under which a future glacier could form involve surprisingly little change from the summit's present climate. The average rainfall would need to increase by only two inches per year and the average temperature would need to drop only a few degrees. Glacial ice would soon form as the result of continued year round accumulations of snow. This condition may have existed in recent times with only the duration being too short. Many early travelers reported that Mauna Kea was known to have a year round cap of snow that "looked down as winter upon summer."

The Top of Mauna Kea
by Pat Duefrene
Aloha magazine
August 1, 1984, v7 n4

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Mauna Kea today

Today, it is not the threat of another ice age that concerns some people. As less and less snow falls on the summit, the implications of climate change for Mauna Kea are unknown.

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As CO2 concentrations have risen, so too has Earth's temperature. Researchers are discovering that a modest rise in temperature of only 1 or 2 degrees Celsius in mountainous regions can dramatically increase the share of precipitation falling as rain while decreasing the share coming down as snow. The result is more flooding during the rainy season, a shrinking snow/ice mass, and less snowmelt to feed rivers during the dry season.

These "reservoirs in the sky," where nature stores fresh water for use in the summer as the snow melts, are shrinking and some could disappear entirely. This will affect the water supply for cities and for irrigation in areas dependent on snowmelt to feed rivers.

Climate Change has World Skating on Thin Ice
By Lester R. Brown
Worldwatch Institute
Hawai‘i Island Journal
October 16 - 31, 2000

 

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