River ice reveals new twist on Arctic melt

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.

Lance Lesack,
photo by Simon Fraser University

Lesack is the lead author on Local spring warming drives earlier river-ice 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.

Mackenzie delta river, before (top) and after
(bottom, one day later) onset of dynamic ice
breakup in the central Mackenzie's delta middle
channel. Photos by Simon Fraser University.

“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.



Backgrounder:

Quotes by Lance Lesack

• “Our work suggests that the effects of reduced winter snowfall should be further investigated in other aspects of the changing Arctic, such as the surprisingly rapid reduction in sea-ice cover and the unexpected collapses of several Canadian ice shelves.” 
• “Our findings should also be of interest to people and industries that exist in the Arctic, where changes in the growth and decay of rivers, lakes or sea-ice may affect their daily lives. Ice roads and shipping over them depend on knowing when the ice roads can be travelled upon or when ferry crossings can be operated during open water.”

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. 
• In 2007 SFU geographer Lance Lesack co-authored a study that found rising water levels in the Mackenzie River delta, induced by climate-related sea-level rise, were three times higher than predicted. The authors worried that the faster-than-expected changes could have important impacts on the region’s human and animal life, and industry.

Press release by Simon Fraser University

http://www.sfu.ca/pamr/media-releases/2014/river-ice-reveals-new-twist-on-arctic-melt.html

Local spring warming drives earlier river-ice breakup in a large Arctic delta
Lance F. W. Lesack, Philip Marsh, Faye E. Hicks and Donald L. Forbes

http://onlinelibrary.wiley.com/doi/10.1002/2013GL058761/abstract

Arctic Ocean is turning red

The Arctic Ocean is turning red, as sea surface temperatures (SST) rise. The NOAA maps below, dated August 12, 2013, show sea surface temperature anomalies across the Arctic Ocean of up to 5°C (9°F). Virtually all areas were the sea ice has disappeared are now colored scarlet red.

[ click on image to enlarge ]

The (updated) animation below shows SST anomalies from June 3 to August 26, 2013.

For a full-size animation, see http://www.ospo.noaa.gov/Products/ocean/sst/anomaly/anim_full.html

Locally, the situation can be even worse. The NOAA map below, dated August 13, 2013, shows that areas where the sea ice has disappeared in the Arctic Ocean can be exposed to sea surface temperature anomalies higher than 8°C (14.4°F).

[ click on image to enlarge ]

These anomalies are very high, even when compared to some of the recent years, when the decline of sea ice extent didn't look as bad as it appears now.

Many people may only look at the sea ice, assuming that things are fine as long as there is no dramatic decrease in sea ice area or extent (see Cryosphere Today image right).

However, there are many other things to consider, as described in the earlier post Cyclone raging over thin ice. Most importantly, sea surface temperature anomalies this high are very alarming!

For comparison, the image below shows August sea surface temperature anomalies in 2007, 2010 and 1011.

from: http://www.arctic.noaa.gov/reportcard/ocean.html

These high sea surface temperature anomalies are firstly caused by higher sea and air temperatures as a result of global warming. Additionally, there are many feedbacks that accelerate the temperature rise in the Arctic, as discussed at the post Diagram of Doom. Local conditions can further accelerate the temperature rise in specific areas, such as where warm water from rivers flows into the Arctic Ocean.

As the map below shows, a number of large rivers end in the Kara Sea, where high temperatures have been recorded for some time.

map from: http://en.wikipedia.org/wiki/File:Rs-map.png

Another large river is the Mackenzie River, which ends in the Beaufort Sea, where sea surface temperatures of about 20°C (68°F) are currently recorded, as the image below illustrates.

Similarly, the NOAA image below shows that sea surface temperatures of up to 18°C (64.4°F) were recorded in the Bering Strait on August 12, 2013.

Note that the melting season still has quite a while to go. Arctic sea ice volume minimum is typically reached around halfway into September, which is more than one month away. On September 12-13, 2011, temperatures of 6-7°C were reached over East Siberian Arctic Shelf, and up to 9°C along the coast of Alaska.

The danger of this situation is that this dramatic rise in temperature anomalies will not remain restricted to surface waters, but that heat will penetrate the seabed which can contain huge amounts of methane in the form of hydrates and free gas in sediments.

Submarine pingoes: Indicators of shallow gas
hydrates in a pockmark at Nyegga, Norwegian Sea -
Hovland et al., Marine Geology 228 (2006) 15–23

At the moment, a cyclone is raging over the Arctic Ocean, and this causes warm surface waters to be mixed down, in many places all the way down to the seabed, due to the shallow nature of many of the seas in the Arctic Ocean.

As shown on the image right and also described at the FAQ page, there can be all kinds of fractures in the sediment, while there can also be conduits where methane has escaped earlier from hydrates, allowing heat to penetrate deep into the sediment and causing methane to escape.

Methane is kept stable inside hydrates as long as the temperature remains low. Since methane expand some 160 times in volume, compared to its compressed frozen state inside the hydrate, warming of even a small part of a hydrate can cause destabilization across the entire hydrate. It may take only a small rise in temperature of a single conduit in the sediment to set off a large abrupt release of methane, which subsequently threatens to cause further releases elsewhere in the Arctic Ocean and trigger runaway global warming, as described at the methane hydrates blog.