Severity of North Pacific storms at highest point in over 1,200 years

August 24, 2017

The intensification of winter storm activity in Alaska and Northwestern Canada started close to 300 years ago and is unprecedented in magnitude and duration over the past millennium, according to a new study from Dartmouth College.

The research, an analysis of sea salt sodium levels in mountain ice cores, finds that warming sea surface temperatures in the tropical Pacific Ocean have intensified the Aleutian Low pressure system that drives storm activity in the North Pacific.

The current period of storm intensification is found to have begun in 1741. According to researchers, additional future warming of tropical Pacific waters - due in part to human activity - should continue the long-term storminess trend.

"The North Pacific is very sensitive to what happens in the tropics," said Erich Osterberg, an assistant professor of earth sciences at Dartmouth College. "It is more stormy in Alaska now than at any time in the last 1200 years, and that is driven by tropical ocean warming."

While the Aleutian Low pressure system sits over Southcentral Alaska in the winter, it can impact weather across the North American continent.

"Storminess in the North Pacific not only impacts Alaska and Northwestern Canada, it creates colder, wetter and stormier weather as far away as Florida," said Osterberg.

The analysis focuses on two ice cores drilled in 2013 from Mount Hunter in Alaska's Denali National Park, and an older ice core from Canada's Mount Logan. The ice cores, each measuring over 600-feet long, offer glimpses into over a thousand years of climate history in the North Pacific through sea salt blown into the atmosphere by winter ocean storms.

The two ice cores from Denali benefited from high levels of snowfall, providing what Osterberg says is "amazing reproducibility" of the climate record and giving the researchers exceptional confidence in the study results.

"That's the other remarkable thing about this research," said Osterberg, "not only are we seeing strong agreement between the two Denali cores, we are finding the same story of intensified storminess recorded in ice cores collected 13 years and 400 miles apart."

While 1741 is noted as the year the current intensification began, the paper also references an increase in storminess in the year 1825. According to the paper, warmer tropical waters since the mid-18th century can be the result of both natural variability and human-driven climate changes.

"There is no doubt that warming tropical ocean temperatures over the last 50 years is mostly caused by human activity," said Osterberg, "a really interesting question is when you go back over hundreds of years, how much of that is anthropogenic?"

Beyond human activity, tropical sea surface temperatures further back in time are affected by volcanic eruptions, changes in the intensity of sunlight and natural events like El Niño.

"The reality of the science is that our changing climate is driven by human causes on top of natural cycles, and we have to disentangle these things," said Osterberg. "This becomes even more critical when predicting climate change over a specific region like Alaska instead of the whole globe averaged together."

Researchers are still waiting to analyze the last 10 meters of the Denali ice cores. The remaining portions could offer information on thousands more years of climate history, but are so compressed that they will require the use of advanced laser tools.

The paper was published last month in Geophysical Research Letters.
-end-


Dartmouth College

Related Ice Cores Articles from Brightsurf:

Ice-binding molecules stop ice growth, act as natural antifreeze
Certain molecules bind tightly to the surface of ice, creating a curved interface that can halt further ice growth.

At our cores, we're all strengthened by 'dumbbells'
Scientists at Rice's Center for Theoretical Biological Physics detail the structure of dumbbell-like sequences in DNA during interphase that suggest several unseen aspects of chromosome configuration and function.

210Pb dating of marine sedimentary cores
Fourteen laboratories participated in this interlaboratory comparison exercise (ILC). The results indicated good analytical performance by the participating laboratories, but the results of the 210Pb dating did not reach the desired level of satisfaction.

Ice discharge in the North Pacific set off series of climate events during last ice age
Repeated catastrophic ice discharges from western North America into the North Pacific contributed to, and perhaps triggered, hemispheric-scale changes in the Earth's climate during the last ice age.

Sea ice triggered the Little Ice Age, finds a new study
A new study finds a trigger for the Little Ice Age that cooled Europe from the 1300s through mid-1800s, and supports surprising model results suggesting that under the right conditions sudden climate changes can occur spontaneously, without external forcing.

Seasonal sea ice changes hold clues to controlling CO2 levels, ancient ice shows
New research has shed light on the role sea ice plays in managing atmospheric carbon dioxide levels.

HIV-1 viral cores enter the nucleus collectively through the nuclear endocytosis-like pathway
How HIV-1 viral cores enter the nucleus through the undersized nuclear pore remains mysterious.

The 'cores' of massive galaxies had already formed 1.5 billion years after the big bang
A distant galaxy more massive than our Milky Way -- with more than a trillion stars - has revealed that the 'cores' of massive galaxies in the Universe had formed already 1.5 billion years after the Big Bang, about 1 billion years earlier than previous measurements revealed.

Evidence: Antarctica's thinning ice shelves causing more ice to move from land into sea
New study provides the first evidence that thinning ice shelves around Antarctica are causing more ice to move from the land into the sea.

Two million-year-old ice cores provide first direct observations of an ancient climate
Princeton University-led researchers have extracted 2 million-year-old ice cores from Antarctica -- the oldest yet recovered -- that provide the first direct observations of prehistoric atmospheric conditions and temperatures.

Read More: Ice Cores News and Ice Cores Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.