There are several soil monitoring stations around Fairbanks but the Bonanza Creek Experimental Forest site ( 64.699030N 148.258742W) is the one I check on the most frequently. The FP1A station is approximately 15 miles southeast of Fairbanks along the Tanana River. The site description is as follows: "FP1A is located on a low early successional terrace (1.8 - 2 m above winter low river level) adjacent to the Tanana River. Vegetation establishment occurred in 1982 to 1983. Significant bank erosion has occurred since the establishment of the study area, resulting in loss of some study plots."
The chart below shows the daily normal temperature (°C) for sensors at 0 cm, 5 cm, 10 cm, 20 cm, 50 cm, 100 cm, and 200 cm between 1989 and 2012 (Note: these are depths below the organic layer at the surface). The small black squares are the November 21st 2013, readings. The color of the square corresponds to the color of the line (the 0 cm and 5 cm boxes are nearly on top of one another). As you can see, the soil temperatures are far above normal for this time of year. In fact, if you look at the table below the chart, the 11/21/13 readings were the highest on record (for the date) for 5 cm and 50 cm sensors during the 25 years of observations.
I am interested is seeing if there is a correlation between ice measurements along the Tanana and the subsurface temperatures.
May the water table temps be driving the soil temps at that shallow water table? Think about the latent heat of water and all the influx this very warm summer into various drainages feeding the Tanana River.
ReplyDeleteGood topic. Surely there are water temp profiles available for the lotics and sub-surface wells. And…it was a very delayed freeze up, possibly due to warm water bodies and warm advection.
Gary
The June through October temperatures in Fairbanks were either the warmest or second warmest on record and that certainly created a thermal wave that is still reflected in the soil temperature profile. The inertia of that wave is slow to transition.
DeleteOk. But was it ultimately an air or water driven thermal wave? Regardless, soil moisture at the various depths may be a factor.
DeleteAnd as you suggest, ice formation and depth along the test site perimeter and elsewhere may be related to either.
Gary
So my previous reply was cut off too soon. Sorry about that Gary. I'll try to remember what else was in there.
DeleteMy guess as to the issue of soil moisture source temperature is that it depends on whether the moisture came from above or from below. If it came from above (rain or melted snow) my guess would be that the temperature of the water entering the system would be pretty constant from year to year. If the moisture source was from the subsurface portion of the Tanana River, it could be more variable. The LTER site is very complicated and I my search for soil moisture parameters came up empty. It's surely there somewhere but I cant find it. Presumably at some depth the soil reaches field (moisture) capacity on a permanent basis and then the soil temperature becomes a proxy for the soil moisture temperature.
Having said all that, my gut feeling is that the temperature profile is almost entirely a function of the air temperature and the ability of the heat to dissipate in the fall/winter dependent on the insulating properties of the snowpack.
http://www.lter.uaf.edu/site.cfm?site_pkey=1
DeleteMy gut feeling is that any locational terrace that proximal to the Tanana River and subject to periodic flooding (1.8-2M above winter low river level) would be influenced by both insolation and the river driven water table below. Surely they have recorded water table temperatures, which by 200 cm down would be real wet.
My post Brian isn't intended to provoke or question your reasoning, but rather question the contribution factors of the source(s) of the elevated soil temps noted.
For some years we seasonally tracked fish (Burbot, Northern Pike, Grayling, and Chum Salmon) implanted with radio transmitters in that section of the Tanana River via aircraft. The area in general is prone to late Summer flooding, and in winter exhibits areas of open water/discontinuous freezing, and surface flooding/aufeis fields via overflowing river water. The river has great control over that environment year round.
Gary
Further info regarding the winter ice condx in the particular area of the Tanana River Brian is discussing:
Deletehttp://jukebox.uaf.edu/site7/dangerice
Gary
I like the Jukebox site Gary. The oral history stuff is especially fascinating to me.
DeleteThere are raw data on that site relative to the topic...and at least a few links to principal investigators at the "U". My wife works with one who spends time researching that portion of the experimental forest unit.
DeleteThe important factors have been noted here. I'd like to learn more about the driving elements affecting the observed soil temps, and their proportional contributions.
Gary
Here's a link to the book referenced above in the Jukebox site regarding winter ice conditions on Interior Alaskan rivers...easy read and very informative:
Deletehttp://jukebox.uaf.edu/site7/sites/default/files/documents/Dangerous%20Ice%20web%202013-08-07-A-1.pdf
In addition, on that site are links to research documents related to the subject:
http://jukebox.uaf.edu/documents/854
Knowledge is power, horses have power, so are horses smart?
Gary
I went through the document you linked to Gary and found it absolutely fascinating. Thank you.
DeleteHi Brian, down in the ham radio shack late and saw your reply. Yes there's nothing like shared Native Alaskan and long term local knowledge. Darwin survival techniques at their best.
DeleteOne topic that's been unaddressed is the potential for and the contribution of subsurface groundwater flow from the upper terrain to the north of the obs station you noted and their temps, versus the Tanana River influence. Complex mixing issues exist no doubt by season, but surely water quality experiments could separate them at various locations an levels below the surface.
No easy trail as some would offer.
Gary