Reconstruction of Ob River, Russia, discharge from ring widths of floodplain trees

Abstract

The Ob is the third largest Eurasian river supplying heat and freshwater to the Arctic Ocean. These inputs influence water salinity, ice coverage, ocean temperatures and ocean circulation, and ultimately the global climate system. Variability of Ob River flow on long time scales is poorly understood, however, because gaged flow records are short. Eleven tree-ring width chronologies of Pinus sibirica and Larix sibirica are developed from the floodplain of the Lower Ob River, analyzed for hydroclimatic signal and applied as predictors in a regression model to reconstruct 8month average (December-July) discharge of the Ob River at Salekhard over the interval 1705-2012 (308 yrs). Correlation analysis suggests the signal for discharge comes through air temperature: high discharge and floodplain water levels favor cool growing-season air temperature, which limits tree growth for the sampled species at these high latitudes. The Highlights • Tree-ring data from the Lower Ob River Basin has a signal for river discharge • Low growth reflects cool air temperatures, driven partly by high water levels • December-July discharge was reconstructed from tree rings back to 1705 • Extremes in discharge on the Ob occurred prior to the start of the gaged record • Reconstructed Ob River discharge is characterized by large multi-decadal swings

Impact of high flows of an Arctic river on ring widths of floodplain trees

“…The Ob River, in western Siberia, is one of the three large Eurasian Arctic rivers that contribute a combined 45% of the freshwater inflow to Arctic Ocean (Shiklomanov et al, 2000). The Ob is attractive as a test site for riparian dendrohydrology because of the presence of undisturbed (by man) stands of riparian trees, previous work in tree-ring chronology development (Agafonov, 1998; Agafonov et al, 2016), and the importance of discharge and flooding to ecology and climatology. The Ob’s inflow of heat and freshwater to the Arctic Ocean is critical to the deep circulation of the ocean and global climate system (Aagaard and Carmack, 1989).…”

Postglacial flooding and vegetation history on the Ob River terrace, central Western Siberia based on the palaeoecological record from Lake Svetlenkoye

“…Presently, approximately 70% of the Ob River annual discharge occurs during the ice-free period from May to October; 80% of the annual runoff originates from south of the 61° north latitude. The hydrological regime of the Ob River is dominated by snowmelt, with peak flows in June to July (Agafonov et al, 2016).…”

“…Western Siberia is a large and diverse region, and thus one of the issues regarding the palaeoecological reconstructions is the scattered palaeobotanical record and differences in local conditions (topography, permafrost, etc). It has been hypothesized that Ob River can influence the local climate characterized by air temperature anomalies related to water level (Agafonov et al, 2016). The main palaeoclimatic trend for the whole region shows the gradual warming in the first part of Holocene and gradual cooling later (Blyakharchuk, 2009) and suggests wet phases in Boreal and Atlantic periods (Groisman et al, 2013).…”

“…The Ob River is one of the largest rivers in the West Siberian Plain flowing into the Kara Sea of the Arctic Ocean. The Ob River contributes about 404 km 3 freshwater per year (Peterson et al, 2002) and is the third largest Eurasian river by runoff, supplying heat and freshwater to the Arctic Ocean (Agafonov et al, 2016). Correlation between the dynamics of the discharge of the Northern Eurasian rivers, North Atlantic Oscillation and global mean surface air temperature suggests that the rivers are responding to hemispheric-scale climatic patterns (Peterson et al, 2002).…”

“…The increased precipitation or decreased runoff probably influenced the rivers; however, there is only limited knowledge on the postglacial palaeoecology, including the flooding history from the Ob region. There are only few remarks that the peat deposited in the wetlands next to the Ob River contains occasional clay and silt layers as a probable result of past river flooding (Mironycheva-Tokareva et al, 2014; Schipper et al, 2007) and one centennial-scale reconstruction from tree-ring record focusing on floodplain hydroclimate and past river discharge estimations (Agafonov et al, 2016).…”