Friday, February 2, 2018

Yukon River at Dawson

Long-time readers may recall a few posts last winter that mentioned the exceptionally slow freeze-up of the Yukon River in Dawson (Yukon Territory).  It's interesting to note that the same thing has happened this winter - there is still a substantial gap of open water that has prevented the construction of the usual ice road to West Dawson.  This year an effort was launched to accelerate the freeze-up with a "slush cannon", but lack of progress led to the project being called off recently.

Here's how the river looked last Sunday.


Last winter we noted that an unusual ice jam upstream was the primary reason for the open water, rather than exceptionally warm weather.  It appears that the same may be true this year, because again the weather has not been particularly warm overall this winter in Dawson; the chart below shows that total freezing degree days through January 22 (when the ice-making project was canceled) were very close to the normal of the last 20 years.



The repetition of the slow freeze-up this winter suggests that it's not a random occurrence - "something" has changed - but the temperature data rules out a simple explanation based on excessive warmth.  I started to look for river flow data from the autumn to see if the river discharge has been unusually high or low, but I had difficulty acquiring suitable data.

One possibility (and this is mere speculation, being outside my field of knowledge) is that there could have been a subtle change in the river profile/cross-section upstream of Dawson, owing to deposition or erosion, that may have altered the hydrodynamics in a way that now favors the formation of an ice jam in a new location.  If any readers have comments on this idea, or other suggestions on how to identify the underlying cause of the open water (i.e. is it related to weather and climate), then I'd be glad to hear them.

13 comments:

  1. It's speculation without data as noted Richard. Altered hydrodynamics, lack of sufficient fetch for ice floes, changes in annual accumulated thermal units (ATU) for the waters of the Upper Yukon watershed, in-stream flow statistics, winter air temps and cloud cover, and so on can affect freezing of the river.

    I do know the fishery and local indigenous people have been installing water temperature recording devices during open water periods so they can monitor that data in relation to stocks of fish they manage or depend upon, particularly King Salmon. There's studies available but maybe not specific to the Dawson location nor for winter periods.

    The Arctic's warming and these things are likely to happen. Both the Yukon and Mackenzie obviously dump into the ocean and any additional warmth or heat flux them will also affect the nearby seas.

    Gary

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    1. http://www.weather.gov/aprfc/riverNotes

      Reportedly open 200' wide by 8-9 miles long at Dawson and possibly similar at Eagle? Something's happening.

      Gary

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    2. Thanks for the comments Gary. Interesting situation at Eagle - the observer measured 42" of ice on January 2, which was well above normal for the date, but 3 weeks later it came in at 30" with open leads downstream as you noted.

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    3. In a couple of hours @ 11 am AST the Yukon Quest race will begin (http://www.yukonquest.com). Follow that event and reports of open water was mushers advance from Fairbanks to Whitehorse. Lots of river travel.

      Gary

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  2. A Google search gave Canada's river data:https://wateroffice.ec.gc.ca/index_e.html

    In particular, Yukon at Dawson: https://wateroffice.ec.gc.ca/report/historical_e.html?stn=09EB001

    It also looks like you can download the whole national river dataset as a database file which might be useful.

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    1. I ran through that link yesterday and it seemed to be seasonal and sometimes limited. Might be the best available tho but in honesty I didn't spend a lot of time mining their rather obtuse interface.

      I suspect a conversation with locals in Dawson that are interested in their world would be revealing, especially if there's been observable changes to the river channel and flow.

      It's all too easy to say it's not been cold enough recently without further examination of the water and climate over time. Fires, soil warming, mining activity also can create change.

      What the Quest mushers and followers encounter will be interesting.

      Gary

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    2. In general, governmental science websites always seem to lack a certain finesse.

      For the last few years, measurements have been seasonal when the ice isn't present. How do you take measurements of a frozen river? Look at the Chena. There is real time measurements during winter but they only show flatlines.

      And speaking of the Chena, last year it was open for a lot longer than normal despite the frozen temps. This is because of the power plant warming the water. It takes time to cool it off. Are there power plants upstream of the open Yukon? If it's only a little warmer that will be enough to keep it open.

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    3. Interestingly enough, http://www.weather.gov/aprfc/ has a few Canadian river sites. Looking at the ones along the Yukon we see what looks to me to be rather high water for winter. But I haven't looked that the historical data to confirm.

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    4. Thanks Eric and Gary. The river data doesn't seem updated and/or comprehensive enough for a robust analysis, but perhaps that will change in later months when the data is finalized.

      I'm inclined to look at weather conditions around the time of freeze-up to see if anything stands out.

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    5. I've done winter water temps and volume in both un and frozen over rivers and lakes. I takes caution and can involve risk at times. For unfrozen river sections a cross channel rope or cable is desired to secure a boat to if deep, or held to if walked in shallow water. Bottom frazil ice if present is slippery.

      Temps over time are usually captured with recoverable recording thermometers but I suspect telemetry has made remote sensing feasible an less risky. For flow and volume there are meters that measure flow velocity, and then depth and width plus channel shape yield volume. I did it by hand in open water, and through holes drilled in the ice when covered.

      Lakes are accessed via holes in the ice and recorders can be placed and recovered. Depth is measured with a line through a hole or fathometer.

      But once winter sets in temps and volume likely stabilize, so Richard's suggestion of examining pre-freeze data might be best. Not many want to analyze flatline data.

      As the river freezes sections can become blocked locally both laterally and vertically thus increasing localized flow velocity to compensate for overall volume. Water may find a way to escape ice cover and restriction if forced and can form open water channels or frozen aufeis fields downstream like those recently along the Dalton Highway.

      Not sure what's happening along the Yukon recently without data.

      Gary

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  3. Outflow of White River into Yukon above Dawson will have dropped as a result of inflow to Kluane Lake bring reduced by glacier changing flow of Slims River. There could be changes in silt load as White carries a lot of silt. Snow depths at Dawson WON, the last couple of years has been around 43cm. Before 2015 snow depths were 55-60cm.

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    1. Thank you! - I had forgotten about the 2016 change above Kluane Lake - is it just coincidence that the freeze-up at Dawson changed the same year?

      Rather incredibly, there appears to be no river flow data for the Kluane or Donjek rivers since 1995, and nothing for the White River down to the Yukon. I'll keep digging around.

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  4. I wonder what influence the nearby Klondike River has on the Yukon next to Dawson during winter? Does it freeze solid or does it/is it still emptying water (maybe warm) into the Yukon just to the left of the webcam's view upstream of Dawson?

    Someone local might know what is does or if there's been any recent changes in that heavily mined tributary's flow and silt load that may affect the Yukon at that confluence?

    Summer Google terrain maps show it as clearer than the Yukon and it hugs the SE bank before mixing. Could there be silt buildup in that area or the source of the ice jam mentioned before?

    Gary

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