Climatological observations from ship logbooks between 1750 and 1854 (release 2.1)

The Climatological Database for the World's Oceans: 1750-1854 (CLIWOC) project, which concluded in 2004, abstracted more than 280,000 daily weather observations from ships' logbooks from British, Dutch, French, and Spanish naval vessels engaged in imperial business in the eighteenth and nineteenth centuries. These data, now compiled into a database, provide valuable information for the reconstruction of oceanic wind field patterns for this key period that precedes the time in which anthropogenic influences on climate became evident. These reconstructions, in turn, provide evidence for such phenomena as the El Niño-Southern Oscillation and the North Atlantic Oscillation. Of equal importance is the finding that the CLIWOC database the first coordinated attempt to harness the scientific potential of this resource represents less than 10 percent of the volume of data currently known to reside in this important but hitherto neglected source.

Results of n-alkane biomarker analyses and paleoclimate reconstruction

The current study presents quantitative reconstructions of tree cover, annual precipitation and mean July temperature derived from the pollen record from Lake Billyakh (65°17'N, 126°47'E, 340 m above sea level) spanning the last ca. 50 kyr. The reconstruction of tree cover suggests presence of woody plants through the entire analyzed time interval, although trees played only a minor role in the vegetation around Lake Billyakh prior to 14 kyr BP (<5%). This result corroborates low percentages of tree pollen and low scores of the cold deciduous forest biome in the PG1755 record from Lake Billyakh. The reconstructed values of the mean temperature of the warmest month ~8-10 °C do not support larch forest or woodland around Lake Billyakh during the coldest phase of the last glacial between ~32 and ~15 kyr BP. However, modern cases from northern Siberia, ca. 750 km north of Lake Billyakh, demonstrate that individual larch plants can grow within shrub and grass tundra landscape in very low mean July temperatures of about 8 °C. This makes plausible our hypothesis that the western and southern foreland of the Verkhoyansk Mountains could provide enough moist and warm microhabitats and allow individual larch specimens to survive climatic extremes of the last glacial. Reconstructed mean values of precipitation are about 270 mm/yr during the last glacial interval. This value is almost 100 mm higher than modern averages reported for the extreme-continental north-eastern Siberia east of Lake Billyakh, where larch-dominated cold deciduous forest grows at present. This suggests that last glacial environments around Lake Billyakh were never too dry for larch to grow and that the summer warmth was the main factor, which limited tree growth during the last glacial interval. The n-alkane analysis of the Siberian plants presented in this study demonstrates rather complex alkane distribution patterns, which challenge the interpretation of the fossil records. In particular, extremely low n-alkane concentrations in the leaves of local coniferous trees and shrubs suggest that their contribution to the litter and therefore to the fossil lake sediments might be not high enough for tracing the Quaternary history of the needleleaved taxa using the n-alkane biomarker method.

Chromatographic fractionation of bitumen from sediments and presence of glycerol ethers in immature sediments (Table 2)

Alkanes having unusual saturated isoprenoidal and methyl-branched structures have been isolated from the bitumen of several sediments. The methanogenic biomarkers 2,6,10,15,19-pentamethyleicosane and squalane were found in sediments which also contained bacteriogenic glycerol ethers. However, in one ether-containing sediment, 2,6,10,13,17,21-hexamethyldocosane was tentatively identified and this compound was found in place of the established alkane biomarkers. Other hydrocarbons found were regular C21 and C23 isoprenoid alkanes, compounds which cannot be derived from phytol; two isoprenoids of the type 3,7,11.-polymethylalkane, previously reported only in petroleums; 8-methylheptadecane, a probable biomarker for cyanobacteria and a number of its homologs and other methyl-branched alkanes. Ubiquitous branched-chain alkylbenzenes and a homology of trimethylalkylbenzenes were also isolated. Most, or all, of the compounds reported here are probably not catagenetic products but may represent direct algal or bacterial bioinputs.