date: Mon Oct 12 12:10:26 1998 from: Keith Briffa subject: copy to a safe place!!and leave original there to: i.Harris@uea >Return-path: >Envelope-to: f023@cpca11.uea.ac.uk >Delivery-date: Mon, 12 Oct 1998 08:27:00 +0100 >Date: Fri, 9 Oct 1998 19:17:12 +0500 >From: Rashit Hantemirov >Reply-To: Rashit Hantemirov >Organization: IPAE >Priority: Normal >Return-Receipt-To: rashit@ipae.uran.ru >X-Confirm-Reading-To: Rashit Hantemirov >To: Keith Briffa >Subject: Short report on progress in Yamal work > >Dear Keith, > >I apologize for delay with reply. Below is short information about >state of Yamal work. > >Samples from 2,172 subfossil larches (appr. 95% of all samples), >spruces (5%) and birches (solitary finding) have been collected within >a region centered on about 67030'N, 70000'E at the southern part of >Yamal Peninsula. All of them have been measured. > >Success has already been achieved in developing a continuous larch >ring-width chronology extending from the present back to 4999 BC. My >version of chronology (individual series indexed by corridor method) >attached (file "yamal.gnr"). I could guarantee today that last >4600-years interval (2600 BC - 1996 AD) of chronology is reliable. >Earlier data (5000 BC - 2600 BC) are needed to be examined more >properly. > >Using this chronology 1074 subfossil trees have been dated. Temporal >distribution of trees is attached (file "number"). Unfortunately, I >can't sign with confidence the belonging to certain species (larch or >spruce) of each tree at present. > >Ring width data of 539 dated subfossil trees and 17 living larches are >attached (file "yamal.rwm"). Some samples measured on 2 or more radii. >First letter means species (l- larch, p- spruce, _ - uncertain), last >cipher - radius. These series are examined for missing rings. If you >need all the dated individual series I can send the rest of data, but >the others are don't corrected as regards to missing rings. > >Residuary 1098 subfossil trees don't dated as yet. More than 200 of >them have less than 60 rings, dating of such samples often is not >confident. Great part undated wood remnants most likely older than >7000 years. > >Some results (I think, the temperature reconstruction you will done >better than me): > >Millennium-scale changes of interannual tree growth variability have >been discovered. There were periods of low (5000-2800 BC), middle >(2800-1700 BC) and high interannual variability (1700 BC - to the >present). > >Exact dating of hundreds of subfossil trees gave a chance to clear up >the temporal distribution of trees abundance, age structure, frequency >of trees deaths and appearances during last seven millennia. >Assessment of polar tree line changes has been carried out by mapping >of dated subfossil trees. > >According to reconsructions most favorable conditions for tree growth >have been marked during 5000-1700 BC. At that time position of tree >line was far northward of recent one. >[Unfortunately, region of our research don't include the whole area >where trees grew during the Holocene. We can maintain that before 1700 >BC tree line was northward of our research area. We have only 3 dated >remnants of trees from Yuribey River sampled by our colleagues (70 km >to the north from recent polar tree line) that grew during 4200-4016 >and 3330-2986 BC.] >This period is pointed out by low interannual variability of tree >growth and high trees abundance discontinued, however, by several >short (50-100 years) unfavorable periods, most significant of them >dated about 4060-3990 BC. Since about 2800 BC gradual worsening of >tree growth condition has begun. Significant shift of the polar tree >line to the south have been fixed between 1700 and 1600 BC. At the >same time interannual tree growth variability increased appreciably. >During last 3600 years most of reconstructed indices have been varying >not so very significant. Tree line has been shifting within 3-5 km >near recent one. Low abundance of trees has been fixed during >1410-1250 BC and 500-350 BC. Relatively high number of trees has been >noted during 750-1450 AD. >There are no evidences of moving polar timberline to the north during >last century. > >Please, let me know if you need more data or detailed report. > > >Best regards, >Rashit Hantemirov > >Lab. of Dendrochronology >Institute of Plant and Animal Ecology >8 Marta St., 202 >Ekaterinburg, 620144, Russia >e-mail: rashit@ipae.uran.ru >Fax: +7 (3432) 29 41 61; phone: +7 (3432) 29 40 92 >Attachment Converted: "c:\eudora\attach\yamal.rwm" > >Attachment Converted: "c:\eudora\attach\Yamal.gnr" > >Attachment Converted: "c:\eudora\attach\Number" >