Here’s an interesting graphic from lecture notes of Jed Schneider and Kathryn Clapp here showing the flow of ice through a mountain glacier. If this is representative of flow in mountain glaciers, one wonders at what exactly is being recorded in a vertical drill hole away from the summit (such as Guliya Core 2). I’ll try to show my query below.
Figure 1. Cartoon of flow in a mountain glacier.
Here is an oversized image of the Guliya glacier from the wonderful Google Earth (there was a poster session showing applications at AGU so get used to seeing more and more of this. (I tried to reduce this in OpenOffice Draw but failed; I used to do this in an ancient Corel Draw, but it crashed my computer when I tried to load it). This image rather closely matches the map in Thompson et al 1996 (NATO, Climatic Variations), which has the most information on the site. The Summit (Site 4) is at 6700 m and the glacier is 103 m thick there (by radar). Site 2 and Site 1 are at 6200 m. The surface flow at Site 2 is 4.7 m/year to the SSE (towards Site 1). The glacier is 308.6 m thick at Site 2 and about 200 m at Site 1 – Site 2 is a topographic bottom. A diagram in Thompson et al 1996 shows radar cross-sections and shows that Site 2 is in somewhat of a valley going NW-SE towards Site 1. The Guliya site is to the W side of Tibet and is said to be affected by the Arabian Sea monsoon (not the SE Asian monsoon).
Figure 2. Google Earth image of Guliya glacier drill sites. 35 17N, 81 29E.
The drill core at Site 2 (308.6 m) has observable dust layers, said to be annual. If the cartoon in Figure 1 above is an accurate representation of mountain glacier flow, I find it hard to picture how the annual layering merely thins, but since there is observable annual layering, it must deform somehow so that the layering is kept intact. I’m not contesting this or suggesting that there’s any misunderstanding by specialists, but equally the flow regimes appear to have non-trivial geometry. In other locations, Thompson appears to have tried to drill at summits. For example, a core in the flow zone at Dasuopu was dated back only to 1922. So one wonders exactly what certainty there is for dating of a core in the flow zone at Guliya. Just wondering for now.
Anyway, Thompson et al 1996 Figure 6 has 4 photographs showing dust layers in 4 core segments – at 82 m, 105 m, 120 m and 135 m. Below is a picture of Guliya layering that I located on the internet. The thickness declines with depth as expected – 16.9 cm at 82 m; 5.0 cm at 105 m; 3.0 cm at 120 m; and 1.7 cm at 135 m. Accumulation in 1991-1992 was said to be about 15 cm – less than the thickness at 82 m – a point which I haven’t seen discussed (but may be in something that I’ve not consulted.)
Figure 3. Interval of Guliya core showing dust layering.
If one uses this information to estimate the count as follows – multiply the lower thickness of the first step by the overlying glacier thickness, then each subsequent interval by the average of the top and bottom layer thicknesses, then one gets 485 years overlying 82 m; another 210 years to 105 m; another 375 years to 120 m and another 638 years to 135 m, making an estimate of the cumulative total of 1070 layers above 120 m and 1708 layers above 135 m. Thompson et al 1996 Figure 8 shows what is said to be a “2000-year history” of accumulation in the upper 132.1 m of the Guliya ice core – which is more layers than yielded by the above simple estimating procedure, but within the same order of magnitude (1708 and 2000 years.)
But when we turn to Thompson et al (Science 1997), one gets something that appears to be an order of magnitude different. Below I’ve rotated the left panel of Thompson (Science 1997) Figure 3 and compared it with the middle panel of Thompson (Science 1997) Figure 4. One is denominated in meters and one in years; here’s my attempt to match them visually. I presume that the uptick at about 265 m corresponds to the uptick at about 110,000 years in Figure 4; that the up-bump around 250-260 meters corresponds to the similar feature from 90-110,000 years; the uptick at 225 meters to the corresponding feature at 75,000 years; the uptick at 135 meters to the feature around 35,000 years; with the up-bumps at about 50 meters corresponding to the features between 5000 and 10000 years.
Top: Rotated Figure 3 form Thompson et al Science 1997; bottom – lower two panels from Thompson et al Science 1997 Figure 4.
Here’s the puzzle: the dust layer counts according to the information from Thompson et al 1996 indicate that 120 meters is about 1000 years old and 135 meters about 1700 years – which indicate a “warm” period leading up to AD1000 or so. In the dO18 version used in Yang et al 2002, the uptick to dO18 values of -12 or so is dated about 200AD (about 800 years earlier.) However in Thompson et al 1997, this is dated (according to my interpretation of the above diagram) around 5000 or 6000 BP.
What is the conclusion – only this – that Thompson ought to archive ALL his data and measurements from Guliya so this can be understood.
Lonnie Thompson website
Meixue Yang, Tandong Yao, Huijun Wang and Xiaohua Gou , 2006. Climatic oscillations over the past 120 kyr recorded in the Guliya ice core, China Quaternary International Volumes 154-155, October 2006, Pages 11-18
Meixue Y, YAO Tandong, W Huijun, GOU Xiaohua ,Correlation between precipitation and temperature variations in the past 300 years recorded in Guliya Annals of Glaciology, 2006
Thompson, L. G.; Mosley-Thompson, E.; Davis, M. E.; Lin, P. N.; Dai, J.; Bolzan, J. F.; Yao, T., 1995. A 1000 year climatic ice-core record from the Guliya ice cap, China: its relationship to global climate variability, Annals of Glaciology, vol.21, pp.175-181
Thompson, L.G., E. Mosley-Thompson, M.E. Davis, P.N. Lin, V. Mikhalenko, and J. Dai. A 1000 year ice core climate record from the Guliya Ice Cap, China and its relationship to global climate variability. Annals of Glaciology, 21, 175-181
Wang Ninglian, Yao Tandong, L.G. Thompson, K.A. Henderson, M.E. Davis. 2002. Evidence for cold events in the early Holocene from the Guliya Ice Core, Tibetan Plateau, China. Chinese Science Bulletin, 47(17): 1422-1427.
Yao, Tandong; Thompson, LG; Qin, Dahe; Tian, L; Jiao, Keqin; Yang, Zhihong; Xie, Chao, 1996. Variations in temperature and precipitation in the past 2 000 a on the Xizang (Tibet) Plateau – Guliya ice core record. Science in China Series D (Earth Sciences). Vol. 39, no. 4, pp. 425-433. 1996.
Yao, Tandong; Jiao, Keqin; Tian, Lide; Yang, Zhihong; Shi, Weilin; Thompson, LG, Climatic variations since the Little Ice Age recorded in the Guliya Ice Core, Science in China Series D (Earth Sciences) [SCI. CHINA SER. D (EARTH SCI.)]. Vol. 39, no. 6, pp. 587-596. Dec 1996.
Yao, Tandong; Thompson, LG; Shi, Yafeng; Qin, Dahe; Jiao, Keqin; Yang, Zhihong; Tian, Lide; Thompson, EM, 1997. Climate variation since the last interglaciation recorded in the Guliya ice core Science in China Series D (Earth Sciences) [SCI. CHINA SER. D (EARTH SCI.)]. Vol. 40, no. 6, pp. 662-668. Dec 1997.
Yao, T., L.G.Thompson, Y.Shi, Q.Dahe., K.Jiao, Z.Yang, L.Tian and E.Mosley-Thompson, 1998. Climate variation since the Last Interglaciation recorded in the Guliya ice cores. Science in China (Series D), 40(6), 662-668.
Yao Tandong, Guo Xuejun, Thompson Lonnie, Duan Keqin, Wang Ninglian, Pu Jianchen, Xu Baiqing, Yang Xiaoxin and Sun Weizhen δ 18 O record and temperature change over the past 100 years in ice cores on the Tibetan Plateau Science in China Series D, 2006