In two of the last three years I have traveled to Fairbanks in February or March. Whenever I go I always stay at Pike's Waterfront Lodge. One year the Chena River was open and the other year the thickness was only 5". However, upstream at the Steese Highway the thickness was quite healthy. This is apparently a common occurrence. But why?
The simple answer is that a power plant between the two sites puts warm, clear water into the River thereby reducing the ice downstream at Pike's Landing. However, the ice thickness is pretty close early in the season at the two sites. Also, Rick noted that another powerplant is upstream of the Steese Highway that generates power for Fort Wainwright. So, there is probably a simple answer but I don't know what it is. Thoughts?
Fig 3. Google Earth screenshot of the two measurement locations. The GVEA Aurora power plant is also shown.
Fig 1. Ice thickness measurements (dots) 2001 to present for Chena River at Pikes Landing and at Fairbanks (Steese Highway).
Fig 2. Smoothed ice thickness 2001 to present for Chena River at Pikes Landing and at Fairbanks (Steese Highway) using monthly averages.
Fig 4. Picture I took of a van stuck on the Chena River Ice Bridge in March 2012.
* Update section *
Google Earth has a 'historical photography' utility that I just decided to check out. Fortunately there is some photography from March 9, 2009, that we can look at. The following four screenshots are ordered from east (Steese Highway) to west (Pike's Landing). The effect of the Aurora Plant is quite apparent. What is still unresolved is why the early season ice at Pike's is 'normal' but it deteriorates quickly in February. Presumably the power plant is in full production mode in December but the ice hasn't started to melt out yet. Perhaps the thermal 'front' takes a long time to make it down that distance from when the pkant operations kick into high gear earlier in the winter.
* Update section *
Google Earth has a 'historical photography' utility that I just decided to check out. Fortunately there is some photography from March 9, 2009, that we can look at. The following four screenshots are ordered from east (Steese Highway) to west (Pike's Landing). The effect of the Aurora Plant is quite apparent. What is still unresolved is why the early season ice at Pike's is 'normal' but it deteriorates quickly in February. Presumably the power plant is in full production mode in December but the ice hasn't started to melt out yet. Perhaps the thermal 'front' takes a long time to make it down that distance from when the pkant operations kick into high gear earlier in the winter.
Fig 5. Google Earth historical image from March 9, 2009 (1 of 4).
Fig 6. Google Earth historical image from March 9, 2009 (2 of 4).
Fig 7. Google Earth historical image from March 9, 2009 (3 of 4).
Fig 8. Google Earth historical image from March 9, 2009 (4 of 4).
By now Brian you know I can't pass by a good opportunity for dialog.
ReplyDeleteThe power plant upstream of Pike's (Aurora Energy) uses Chena River water for cooling purposes, and discharges the heated effluent back into the river. That in turn affects both the water temperature and thickness of ice downstream. Ft. Wainwright uses contained cooling ponds for its power plant, at least it used to years ago.
http://groundtruthtrekking.org/static/uploads/files/EPA-PA-Fairbanks-Coal.pdfGOqKVt/EPA-PA-Fairbanks-Coal.pdf
In addition, in my experience and observation the water level of the Chena River falls during winter. As a consequence, the stream margins can gradually freeze to the bottom, and the river exhibits a readily visible concave slump to its surface by Spring.
What that can mean is that in width constrained areas (like Pike's) the volume of water is forced to accelerate in order to pass. That, and heat, can affect the thickness of the surface ice cover.
One winter in the late '80's we parked two planes downstream of Pikes and across from the Riverboat Discovery. As winter progressed into Spring (but before warm air temps prevailed), the ice thickness decreased in spots (we drilled holes for tiedowns), and open spots and overflow developed in mid channel. We blamed the power plant and the constraint of flow for the problem.
Gary
Thanks Gary. As you stated, a constricted channel accelerates the water flow which works against the ice thickness. A quick measurement on Google Earth shows the two areas to be approximately the same width. That being said, I'm not sure exactly where the Steese Highway measurement is taken.
DeleteSo does the Fort Wainwright power plan let their heated water cool before re-entering the river? f so, that would make an enormous difference.
Still, if the power plant effluent was the driving force, the early season similarities would not be evident. Plus, why February for the decline and not March.
I wonder if the opening of the Ice Bridge itself has an influence on the ice thickness.
Hi Brian. Its hard to condense all potential aspects for the thinning in a short reply. Here's some more.
DeleteRiver bottom morphometrics play a role in freeze depth and flow constriction. Offhand I can't compare both the Pike's and Steese Bridge river bottoms...maybe we need to cross and take fathometer readings through the ice someday.
As far as I know, Ft. Wainwright uses contained cooling ponds that likely extend below the prevailing water table. We kept Sheefish in one years ago, and boated about in mid-winter as they remain open from the heated input. I don't believe they flow into the Chena river above the Steese highway.
The ground water flow at Pike's is likely influenced by the nearby airport and float pond (water flows downhill and to the west under Fairbanks). Residual heat input from that area may affect the ice depth at Pike's later in the season. Not sure but summer heat may warm the soils under the exposed airport surface to depth.
The Aurora Energy plant produces the most heated water during times when most cooling is required for electric power and heat generation...I assume that's normally during cold dark mid-winter versus warmer March with more daylight, when things tend to warm up around here. Pike's is downstream of course, and there's open water today under the University Avenue bridge upstream.
When we speak of ice do we mean "undisturbed ice" or ice subject to growth in thickness through overflow? The area of the Chena above the Steese is quite shallow in spots. I haven't kept track but it may be subject to more overflow (from subsurface damming in spots) and surface refreezing during cold spells than at Pike's, which as I recall, is a channel capable of floating the small riverboats that overwinter in the pond next to the George Parks Highway bridge upstream.
But in the end, maybe that's just how things are to be...more ice at the Steese, and less at Pike's in late winter.
Gary
Good stuff Gary.
DeleteThe Chena is readily accessible of course. Maybe some simple temp readings are in order? Above the Aurora power plant, just below, then in progressive steps to Pike's. Lob or lower a calibrated min-max therm in the creek and see what it says upon retrieval.
DeleteF&G built the Ruth Burnett hatchery here. At first they used Aurora water of some sort (I wasn't involved) to rear test fish. When the City backed away from a chosen location adjacent to the Chena downstream that would have offered heated water plus other sources, the State relocated away from the river. Wells at the current site apparently were colder than at the test facility near the river, and the water was of poor quality for their purposes (so I've read).
Moral: The power plant and main Chena River thalweg were warmer than the adjacent water table. That may apply to upstream of the Aurora plant as well.
Gary
NOAA's chena river website, for those who want to know, is at http://water.weather.gov/ahps2/glance.php?wfo=pafg&riverid=203485
ReplyDeleteAir temps and snow make a difference on ice compactness. We do get more general snow in March.
Good link Eric. Surely NOAA or similar agency has studied the Chena River's thermal regime in winter.
DeleteMany years ago I used recording mechanical therms to characterize the water temps in the Delta Clearwater River north of Delta Jct. It's groundwater sourced from the Alaska Range to the south, and remains ice free over most of its upstream length down to 40-50 below. 39F at the source springs year round.
At those very cold winter temps, ice forms on both the top, bottom (anchor or frazil ice), and sides of the stream, forcing the main flow through a tube in the ice. When it warms, the ice disappears except for surface cover in the lower extremities.
At the time I lived 50' from the river and watched it all happen.
Gary
I right now live 100' from the Chena near the airport. The river some years ago was dredged for the riverboat. Thus they made the east side significantly deeper than the west side. The east side always freezes last and thaws first. This tells me that the speed of the river is the next biggest factor to ice thickness besides temp. And speed is determined by volume which varies throughout the year. The river is particularily low right now because of the hot summer and warm fall.
DeleteThe Google map above should have a mark on the power plant. The power plant is downtown Fairbanks, a few miles from Pikes. Anyone not from Fairbanks wouldn't easily know this. And I think we do have many international viewers.
Thank you Eric. That is an excellent suggestion. I replaced the map with a new one showing the power plant location.
DeleteCan you tell me what the February/March ice conditions are like upstream of Pike's? That would help diagnose the relative contribution of the power plant's warm water vs. the local channel morphology.
Hey Brian...saddle up and come to Fairbanks for a look at the Chena. There's open water here and there, and if you had some sampling gear you could take temps and document temp gradients. I have an ice spud if you wanted to make some holes. Just a thought.
DeleteGary...
The post was updated to include Google Earth historical imagery from March 9, 2009, and a brief update section.
ReplyDeleteThank you all for the careful observations and comments. I am an engineer working on the replacement of the University Avenue bridge and have relied upon your ice thickness observations (along with local news paper articles associated with the annual Sonot Kkaazoot: http://www.newsminer.com/news/local_news/river-ice-quickly-deteriorating-in-interior-alaska/article_b13aaee4-f8aa-11e5-b81c-a7d1e96b0dca.html)
ReplyDeleteKindly,
Nathan Jaques, P.E.
Hi, I'm working on a story about this is there any way I can contact you? My email is TheMattRalston@gmail.com
ReplyDelete