Polar Ice Melting Far Faster Than Officially Predicted
Like everything else related to global warming and climate change, at both ends of the globe, polar ice is melting far faster than officially predicted.
In the Arctic
In the Arctic, warming projections are now so dire that current official calculations suggest the Arctic could be completely ice-free by 2040 (unofficially it will likely be ice-free much sooner – perhaps even this year).
Though that is only 22 years away, the melting rate on a daily or even monthly basis is still slow enough that in most places in the Arctic it is usually hard for casual observers to see how bad the warming trends are. This year, however, with the months of December through March affected by a serious heat wave never seen before, the melting is becoming a lot easier to spot.
One of the best examples of this is seen in Alaska’s Denali National Park. There, the glaciers are melting faster than during the past four centuries.
Because of global warming, snow on the park’s Mt. Hunter is melting at a rate over 60 times greater than during the summer before the industrial period started – about 150 years ago. The rate is so rapid that according to a new study published by lead author Dominic Winski in the Journal of Geophysical Research: Atmospheres (a journal of the American Geophysical Union), more snow now melts on Mt. Hunter than at any time during the past 400 years.
Winski is a glaciologist at Dartmouth College in Hanover, New Hampshire.
Based on new ice-core samples taken from Mt. Hunter’s summit, summers there are now running a minimum of 1.2-2°C (2.2-3.6°F) warmer than at the same time of year in the 18th, 19th and early 20th centuries. The warming at the summit is about twice that which occurred at sea level in Alaska during the same time period.
Those cores were drilled at the summit plateau of Mt. Hunter, at a level of 13,000 feet above sea level. The samples provide a graphical means of understanding past weather patterns, as the darker ice bands without bubbles suggest times when glacial snow melted in the summers and then re-froze. When a given year produced more melt events (and more dark ice bands), that means the summer was warmer.
Based on the data observed this way, the research team determined that melt events are happening 57 times more often than 150 years ago. There were in fact only four melt event years before 1850. What that suggests is that the total meltwater produced in the cores in recent times is 60 times what it was during the previous 150 years.
This also ties in with the hotter temperatures currently being recorded in the tropical Pacific Ocean. That area, like elsewhere in the world, has seen significant temperature increases since the mid-1950s as a result of increased greenhouse gas emissions. The researchers believe the warming tropical Pacific is creating warm air currents that are moving to the earth’s polar regions. With few high mountain ranges in the way near the tropics, the air can migrate faster and farther than had previously been believed. That is part of why the poles seem to be seeing far more extreme heat – and resultant glacier melting – than regions closer to the equator.
According to Luke Trusel, a glaciologist at Rowan University in Glassboro, New Jersey, who saw the Mt. Hunter study’s research but was not part of the work, “this adds to the growing body of research showing that changes in the tropical Pacific can manifest in changes across the globe. It’s adding to the growing picture that what we’re seeing today is unusual.”
In the Antarctic
While the Arctic has been well-known to be in trouble from global warming, scientists were seeing a far more stable scenario in the Antarctic. There, the ice seemed to be melting slower and more erratically. There were still problems there but nowhere near the magnitude of those in the Arctic.
A new study revealed at the end of March 2018 has unfortunately changed all past thinking on that. Based on the data, it looks like Antarctica will likely soon become the biggest source of sea level rise in the world. That puts the current front-runner from that list, Greenland, into the number two slot.
The reason for this surprise is that up until now the rate of melting of Antarctic ice sheets was estimated solely by looking from above. It was assumed that the sun and warmer air from above, along with warmer water ocean currents lapping the edges of the sheets, were the main contributors to their melting.
That assumption is wrong, according to researchers from the University of Leeds, who conducted the new study. It turns out that the anchor ice for the sheet, which runs under the ice sheet, is melting at a much higher rate than the part above water. The melting rate for the underwater part of the ice is, of course, ultimately what determines sea level rise, and that’s a big problem.
Some of the ice in the Antarctic runs as deep as two kilometers (1.2 miles) underwater. That is a lot of ice to be melting so fast.
The trick that allowed the researchers to discover the error in calculating melting rates was mapping the “grounding lines” that separate the top part of the ice sheet with the underbelly below. The researchers found a new way to map those grounding lines and analyze just how fast they were retreating across the Antarctic sheets.
According to the study’s lead author, Hannes Konrad, they learned that warming ocean waters have in five years eaten away an area of underwater ice approximately the size of Greater London. The ice has either completely melted or is drifting toward the warmer ocean waters northward of the Antarctic region, where it will eventually break into smaller pieces and then melt completely.
The researchers also found that approximately 25% of the West Antarctic glaciers are melting at a faster rate than the ice stream did at the end of the last ice age. That raises serious concerns, since at that time – 20,000 years ago – sea levels were about 120 meters (394 feet) lower than they are today.
The team is trying to come up with exact predictions of the average rate of melting of the Antarctic sheets. Also of interest are the compounding effect and corresponding melting acceleration that happen as the ocean waters warm in general. That will get more serious as global warming itself increases.the growing warming of the globe will only make all this worse as time goes on, warming the tropics, melting the Arctic, undermining the lower part of the Antarctic ice sheets and causing rising seas across the planet. It is further evidence of the urgency with which the entire world needs to respond to this catastrophic worldwide problem.