New Paleoclimate Records from the Russian Far East: Carbon Accumulation Rates and Ecological Change Over the Last 13,000 Years from Western and Central Kamchatka

Abstract:

The Kamchatka peninsula lies along the confluence of the Pacific Ocean, and the Bering and Okhotsk Seas (OS). Its location is ideal to record shifts in regional ocean and atmospheric circulation and contains vast stores of carbon-rich peatlands, yet paleoclimate records from this area are scarce. This research aims to provide new paleo-proxy records that document carbon dynamics, precipitation, and temperature over the Holocene.

We focus on site C4 (54.02 N, 156.13 E) located 18 km from OS coast at 91 m elevation and draw comparisons with site C1 (54.91 N, 156.60 E) which is 62 km from the coast at 256 m elevation, both in the Western Lowland (WL) region. Cores C1 and C4 are 450 and 375 cm in length, respectively. C4 and C1 were analyzed for organic matter (OM) content; while C4 received additional δ-deuterium (δD), plant macrofossil, and fossil pollen analysis. Both cores cover the last 13,000 years from the Western Lowlands (WL); prior to this study no such records existed from the WL or the eastern OS coastline. Chronologies are based on radiocarbon dating of fine fraction bulk peat and Sphagnum plant macrofossils.

At both sites, peat accumulation began 11 ka (1 ka = 1000 calibrated years before present), is continuous to the surface, interlayered with tephra, and overlays a clay unit with 20% OM. OM density measured at 1 cm intervals show similar means of 0.1 g cm^-3 over the last 11 ka and, despite the close proximity of the sites (103 km), they show two opposing OM trends: Period 1) From 5.8 to 3.5 ka, C1 OM density decreased ~0.10 to 0.06 g cm^-3 while C4 increased from ~0.10 to 0.19 g cm^-3, and Period 2) from 3.5 to 0.9 ka, C1 OM density increased to ~0.18 g cm^-3 while C4 decreased to ~0.11 cm^-3. Peat carbon accumulation rate (PCAR) is similar for both periods in C1 and C4 at 20.1 and 14.1 g m^-2 yr^-1, respectively. Prior to 5.8 ka PCAR in C1 and C4 is ~30 g m-² yr^-1 in the early Holocene, decreasing to 19 g m^-2 yr^-1 in the Mid- Late Holocene. C4 shows large PCAR increase to 50 g m^-2 yr^-1 from 8-7 ka. Paleoenvironmental syntheses of the WL show Period 1 and Period 2 correspond to cooling and warming phases, respectively, while a wet-temperate phase corresponds with higher PCAR in C4. Disagreement in C4 and C1 might be related to proximity with the OS; reflecting shifts in OS circulation and sea ice cover. Pending results of Sphagnum ðD from C4 might serve as a proxy for the OS.