Graumlich  argued that it was "difficult" to compare the results of Lamarche et al  and Graybill  to Kienast and Luxmoore  results, because 15 of 16 Lamarche-Graybill sites came from above 2800 m, while 30 of 34 Kienast and Luxmoore sites came from below 2000 m. While this is true, the two high-altitude Kienast and Luxmoore sites (Niwot Ridge and Arapahoe PCEN) come from a location that is very close to one of Graybill’s sites (Niwot Ridge PIFL). In fact, in this one overlapping case, the Kienast-Luxmoore sites actually come from slightly higher altitudes than the Graybill site and appear to be very close. Before doing the comprison, I thought that it would be interesting first to check out information on the site, check any other collections in the area.
In addition to these three collections, I was able to identify 2 other collections from the area, one a bristlecone sample taken in 1980 and one a PIFL site at a very similar altitude to the Graybill PIFL site taken a couple of years later up to 1989. No results have been archived from Niwot Ridge in the last 16 years. (For high-altitude sites i.e. above 3000 m in Colorado, no measurements have been archived for the last 12 years; 4 sites were archived in the early 1990s: two PCEN, one PIFL and one bristlecone – I’ll discuss these on another occasion).
|Site/Species||Lat (o ‘)||Long||Alt (m)||End||Author|
|Niwot Ridge PCEN co083||40 04||105 35||3700||1979||Hansen-Bristow|
|Niwot Ridge PCEN co574||40 03||105 34||3400||1983||Schweingruber|
|Arapahoe PCEN co517||40 03||105 35||3320||1983||Kienast|
|Niwot Ridge PIFL co545||40 03||105 33||3169||1987||Graybill|
|Island Lake PIFL co511||40 02||105 35||3200||1989||Woodhouse|
One of the reasons for the lack of any updates since the 1980s is undoubtedly the rigors of getting to the site and bringing the samples back to civilization, in line with Mann’s comments at realclimate about the need to rely on samples taken from the 1970s and 1980s because of the expense and time needed to collect new samples.
Niwot Ridge is no less than 35 miles west of UCAR/NCAR headquarters in Boulder, Colorado and the drive is reported to take no less than 45 minutes. Intrepid explorers must plan an expedition for days in advance and are advised to pack a lunch. In this forbidding wilderness, explorers will be relieved by the vista of the Niwot Ridge Long-Term Ecological Research Station, established by NSF in 1980, continuing previous installations of the University of Colorado. Explorers unprepared for the rigors of this expedition can take a virtual field trip and even view live-cam images here and here . There are not one, but six meteorological stations, at varying altitudes up to 3743 m.
Here is a map of the Niwot Ridge area (from 40 00 45N to 40 04 15N; from 105 32 to 105 29W):
It looks to me like the Schweingruber, Kienast and Graybill samples are all taken just to the east of the "Subalpine Subniveau Lab". Taking these samples might well have required a hike of 1-1.5 miles off the road to the laboratory. One can well understand why no explorer has re-sampled in such a dangerous location for nearly 20 years. Island Lake – the location of the Woodhouse samples – is the lake just to the west of Silver Lake, a couple of miles south of the lab. I can’t quite figure out where the Hansen-Bristow samples were taken from from the location map and the sketchy information on lat-long-altitude (which may not be consistent). I’ll post up the site chronologies tomorrow.
Other background information: it seems to me that many of the roads into the mountains were originally due to 19th century mining camps (which were typically very small vein mines that would be hard to locate today without a detailed location map) and I like to check out mining information related to these sites. There was a Niwot mine in the area mentioned here
The Ward district is 9-13 miles northwest of Boulder. It covered 12 square miles in headwaters of Lefthand and Fourmile Creeks. The old camps of Sunset and Copper Rock, more than 50 lode mines in area, had a total production of 172,000 ounces of lode gold. The Niwot and Columbia mines were the largest producers of lode gold. In east part of district, many mines produced gold in tellurides.
A continuous climate record since 1951 at Niwot Ridge in the Colorado Front Range shows a decline in mean annual temperature, an increase in annual precipitation amount, and a decrease in mean daily solar radiation for the summer months. The increase in precipitation amount explains about half of the 200% increase in annual wet deposition of NO3- to Niwot Ridge over the last decade. Differences in climate parameters between 1994 and 1995 (increased snow depth and decreased net energy flux to the snowpack) resulted in a 4 to 5-fold increase in the magnitude of solute release from the snowpack in the form of an ionic pulse. In turn, the high chemical loading of strong acid anions in the seasonal snowpack and release of these solutes from the seasonal snowpack in the form of an ionic pulse is causing episodic acidification (ANC < 0 meq/L) in headwater catchments at present deposition levels. Small changes in climate parameters may cause large changes in the hydrochemistry of alpine streams. The changes in climate at Niwot Ridge are not in synchrony with lowland warming in the Great Plains to the east of Niwot Ridge and serve as a reminder that climate in alpine areas is driven by local conditions and may be asynchronous with regional and global climate trends.
Nitrogen Saturation in the Rocky Mountains: Nitrogen (N) saturation is occurring throughout high-elevation catchments of the Colorado Front Range. Annual inorganic N loading in wet deposition to the Front Range of about 4 kg/ha/yr is about twice that of Pacific States and similar to many sites in the northeastern US. In the last ten years at Niwot Ridge/Green Lakes Valley and Glacier Lakes, annual minimum concentrations of NO3- in surface waters during the growing season have increased from below detection limits to about 10 meq/L, indicating that these two catchments are at the threshold of N saturation. The Loch Vale watershed is N saturated, with annual minimum concentrations of NO3- in surface waters generally above 10 meq/L; annual volume-weighted mean (VWM) concentrations of 16 meq/L NO3- in surface waters are greater than that of about 11 meq/L NO3- in wet deposition. At these high-elevation catchments there has been a shift in ecosystem dynamics from an N-limited system to an N-saturated system as a result of anthropogenically-fixed N in wetfall and dryfall. Results from the Western Lakes Survey component of the National Surface Water Survey show that N saturation is a regional problem in the Colorado Front Range, with many lakes having (NO3-) concentrations greater than 10 meq/L. Foliar N to P ratios in Bristlecone Pine increase with elevation in the Colorado Front Range, indicating that at higher elevations P is translocated from foliar tissue more efficiently than N and that increasing atmospheric deposition of N with elevation is causing a change from N limitation to P limitation in the highest-elevation Bristlecone Pines. Current concepts of critical loads need to be reconsidered since only modest atmospheric loadings of N are sufficient to induce N leaching to surface waters in high-elevation catchments of the western United States.