River ice reveals new twist on Arctic melt

Apr 02, 2014
Images show before (lower) and after (upper, one day later) onset of dynamic ice breakup in the central Mackenzie delta's middle channel.

A new study led by Lance Lesack, a Simon Fraser University geographer and Faculty of Environment professor, has discovered unexpected climate-driven changes in the mighty Mackenzie River's ice breakup. This discovery may help resolve the complex puzzle underlying why Arctic ice is disappearing more rapidly than expected.

Lesack is the lead author on Local spring warming drives earlier river- breakup in a large Arctic delta. Published recently in Geophysical Research Letters, the study has co-authors at Wilfrid Laurier University, the University of Alberta and Memorial University.

Its goal was to understand how warming global temperatures and the intensifying Arctic hydrological cycle associated with them may be driving increasing water discharges and more rapid ice breakup in the Arctic's great rivers.

But the researchers stumbled upon an unexpected phenomenon while trying to figure out why the Mackenzie River's annual ice breakup has been shortening even though its water discharge isn't increasing, as in Russian rivers.

Just slightly warmer springs with unexpected snowfall declines—rather than warmer winters or increasing river discharge, as previously suspected—can drive earlier-than-expected ice breakup in great Arctic rivers.

The Mackenzie exemplifies this unexpected phenomenon. The researchers discovered this by accessing records dating back to 1958 of the river's water levels, snow depths, air temperatures and times of ice breakup.

This finding is significant, as Arctic snow and ice systems are important climate-system components that affect the Earth's ability to reflect solar radiation.

"Our surprising finding was that spring temperatures, the period when river-ice melt occurs, had warmed by only 3.2 degrees Celsius. Yet this small change was responsible for more than 80 per cent of the variation in the earlier ice breakups, whereas winter temperatures had warmed by 5.3 degrees but explained little of this variation," says Lesack.

"This is a strong response in ice breakup for a relatively modest degree of warming, but further investigation showed that by winter's end snow depths had also declined by one third over this period. The lesser snow depths mean less solar energy is needed to drive ice breakup."

Lesack says this is the first field-based study to uncover an important effect of reduced winter snowfall and warmer springs in the Arctic—earlier-than-expected, climate-change-related ice breakup.

"The polar regions have a disproportionate effect on planetary reflectivity because so much of these regions consist of ice and snow," says Lesack. "Most of the planetary sea ice is in the Arctic and the Arctic landmass is also seasonally covered by extensive snow. If such ice and snow change significantly, this will affect the global climate system and would be something to worry about."

Lesack hopes this study's findings motivate Canadian government agencies to reconsider their moves towards reducing or eliminating ground-based monitoring programs that measure important environmental variables.

There are few long-term, ground-based snow depth records from the Arctic. This study's findings were based on such records at Inuvik dating back to 1958. They significantly pre-dated remote sensing records that extend back only to 1980. Without this longer view into the past, this study's co-authors would still be in the dark about the more rapid than expected Arctic melt and planetary heat-up happening.

Facts:

Canada's Mackenzie and several Russian rivers are among the Arctic's gigantic waterways. The hydrological cycle is the cycling of water from the oceans to the atmosphere and back down to the continents, which the rivers then drain back to the ocean. Planetary warming hastens this cycle, which should lead to higher river discharge, more rapid river ice breakup, and ultimately more extreme weather patterns.

About a third of the size of Switzerland and reaching 200 kilometres inland, the Mackenzie River delta sits at the end of Canada's longest river and sustains 45,000 lakes.

The Mackenzie River delta and other Arctic deltas are considered biological hotspots because their sites have much higher biological productivity and biodiversity than their surrounding Arctic environment. Their peak river levels enhance marine ecosystems by flushing nutrients and organic matter from vast deltas that sit at freshwater-ocean water interfaces into the ocean.

Explore further: Researchers find temperature feedback magnifying climate warming in Arctic

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User comments : 11

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TegiriNenashi
1 / 5 (10) Apr 02, 2014
Breakup of arctic rivers is well documented, so there is little room for AGW Bad Science. Check up
http://www.nenana.../ice.htm
if there is any trend. The ice thickness as of Mar 30 is 36 in -- exactly the same as it was 25 years ago:
http://www.nenana...1990.htm
Maggnus
5 / 5 (13) Apr 02, 2014
What is it about deniers and comprehension?

The article doesn't say anything about ice thickness, it says the river ice breaks up sooner than it used to. If you are going to deny something, at least pick on the subject of the article!
TegiriNenashi
1 / 5 (11) Apr 02, 2014
What world are you living in? In real world ice thickness is correlated with temperatures. It is also correlated with breakout date. I'm focusing on ice thickness because they provide around 12 data points during each season (as opposed just one point -- breakout date). It is just more data, which implies more robust conclusion.
ScooterG
1 / 5 (10) Apr 02, 2014
"Its goal was to understand how warming global temperatures and the intensifying Arctic hydrological cycle associated with them may be driving increasing water discharges and more rapid ice breakup in the Arctic's great rivers."

They went in with pre-conceived notions of global warming. Since global warming cannot be proven, the entire study is a waste of time and taxpayers money.

MandoZink
5 / 5 (10) Apr 03, 2014
They went in with pre-conceived notions of global warming. Since global warming cannot be proven, the entire study is a waste of time and taxpayers money.


For a couple of decades the phenomena of increasingly earlier thaws and breakups has been in the news. These events have traditionally recurred within consistent seasonal windows for centuries in Northern America. They've been annually noted and locally observed. How old do you need to be to have any sense of the abnormality of the historical divergences occurring?

Contrary to the quoted comment, It is totally prudent to investigate what's influencing a divergence from the norm, especially in light of the climate consensus. Purposely ignoring these anomalies would be stupid.

You probably aren't old enough to have been gardening for decades either. Growing seasons keep getting longer and hotter. Many of us actually want to know why.

I hope someday you won't have to assure your grand-kids there really was ice at the poles.
aksdad
1 / 5 (9) Apr 03, 2014
These events have traditionally recurred within consistent seasonal windows for centuries in Northern America.

Really? I thought records dated back to 1958. I wonder when thaws and breakups happened during the Medieval Warm Period (~950 to ~1250 AD) when global temperatures were comparable or warmer? Any old Inuit writings on the subject? No? So perhaps "abnormal" only with respect to the period 1958 to 2013.

I'm curious about how "disproportionate" an effect on "planetary reflectivity" the snow and ice of polar regions really has. They are so far from the equator that sunlight hits them at an extremely oblique angle, much like the sunlight near sunset in more temperate latitudes.
MandoZink
5 / 5 (9) Apr 03, 2014
Really? I thought records dated back to 1958.

The article referred to the "ground-based snow depth records" that dated back to 1958 from Inuvik, the particular locality on the Mackenzie River where they did this study.

I was referring to the numerous thaws and breakup events that inhabitants in northern areas have been noting and celebrating for hundreds of years. There have been a variety of local traditions, wagers and get-togethers to commemorate these annual happenings. Locals have been noting what week/day/hour, and often the minute that events occur. They bet on it and have been reporting those thaws occurring dramatically earlier in the last few decades.

I wonder when thaws and breakups happened during the Medieval Warm Period (~950 to ~1250 AD) when global temperatures were comparable or warmer?

Over the last 50 years the Northern Hemisphere has grown considerably warmer than the MWP. It is also occurring substantially faster than any previous warming.
aksdad
1 / 5 (6) Apr 04, 2014
I was referring to the numerous thaws and breakup events that inhabitants in northern areas have been noting and celebrating for hundreds of years.

Exactly. Anecdotes and oral traditions aren't very accurate measures of climate trends. And if you're referring to this tradition:

http://www.nnsl.c...ofd.html

It only dates back to the 1970's, not "hundreds of years".

Numerous proxy temperature reconstructions show the Medieval Warm Period to be comparable to today, and maybe even warmer...and other proxy studies show the opposite. Proxy temperatures are better for showing trends than absolute temperatures.

The rate of warming from 1910-1940 is very similar to 1970-2000, but the IPCC doesn't attribute the earlier warming to human influence (atmospheric CO2 was much lower then).

http://www.cru.ue...RUT4.png

Note there has been no warming since about 1998.
MandoZink
5 / 5 (5) Apr 04, 2014
Well here's something you might check out -
https://www.natur...mate.pdf

This is is a PDF file explaining an extensive study of Canadian icing and melting events at nearly 950 sites. They detail the decreasing freeze-over days that have been the trend in the last decades.

From the document:
"The combined ice records date from as early as 1822 and as late as 2007. Together, the programs have collected data from approximately 950 sites across Canada. The longest series of records span 165 years, but most series are short: 303 sites have just one or two years of data"

Historic wagering is also noted:
"Dawson City Ice Pool
In 1896, prospectors in Dawson City, Yukon bet on the exact minute when ice break up would begin on the Yukon River. A bell attached to a cord tied to tripods on the river signaled the first shifting of the ice. The Ice Pool has become an annual tradition since that first winter."
MandoZink
5 / 5 (5) Apr 04, 2014
This is from a Canadian volunteer observer initiative site:

"As citizen scientists, IceWatch volunteers are contributing to a scientific understanding of climate change. By analyzing citizen records, scientists have found that the freeze-thaw cycles of Northern water bodies are changing. However, since climate change is not consistent across the country and there are large gaps in the current monitoring network, scientists require critical data from many more regions. A citizen network of IceWatchers spread throughout Canada can help to supply that information.

Ice events - the freeze and thaw dates of lakes and rivers - are easily recorded yearly changes that, with your assistance, can help us to monitor the effects of climate change on Canadian ecosystems. All observations, provide essential information that can be used in analysis of climate records. However, Long-term ice data sets and records from areas where we have little geographic coverage are particularly valuable."
MandoZink
5 / 5 (5) Apr 05, 2014
Note there has been no warming since about 1998

About that "no warming" thing.
http://www.skepti...ists.jpg

IPCC predictions also include periodic pauses in the long-term warming trend, as the records reflect. The climate then resumes it's heating progression following the temporary lulls.