Differential North Atlantic control of winter hydroclimate in late Holocene varved sediments of Lake Kortejärvi, eastern Finland

Abstract

Sediment microfacies, geochemical l-XRFand X-ray density analyseswere conducted onvarved sediments from Lake Kortej€ arvi (eastern Finland) covering the last 2700 years. The varves comprise couplets of detrital and organic sublayers throughout the complete time-span. Based on their microfacies and stratigraphical position within a varve as well as comparisons with local discharge and meteorological data, thicker detrital layers are interpreted to reflect intensified snow-melt floods following more humid winters. Detailed comparisons with monthly to annually resolved North Atlantic Oscillation (NAO) indices back to AD 1049 (901 a BP) suggest that multidecadal increases in snowmelt layer thickness tend to be connectedwith a more positive phase of the NAO and, consequently, warmer winters. In contrast, distinct centennial intervals of thicker snow-melt layers from À40 to 170, 280 to 460 and 1900 to 2300 a BP as well as around 2600 a BP do not consistently correspond to a particular NAO phase, but coincide with extended sea-ice margins and a colder North Atlantic climate, causing intensified and southward shifted westerly cyclones. Our results point to a differential modification of North Atlantic winter hydroclimate working on varying time scales.

Reconstructing past hydrology of eastern Canadian boreal catchments using clastic varved sediments and hydro-climatic modeling: 160 years of fluvial inflows

“…Anthropogenic environmental impacts on watersheds can be preserved in varved lake sediments (Zolitschka et al, 2015;Saarni et al, 2016;Czymzik et al, 2018). The welldeveloped sub-layers of Grand Lake varves deposited prior to 1972 CE from sites NAS-1 (Fig.…”

“…Temp-Spring (Tab. 3), demonstrate that Grand Lake varve predominantly reflects spring discharge conditions (e. g. Ojala and Alenius 2005;Lamoureux et al, 2006;Saarni et al, 2016;Czymzik et al, 2018), which is the major component of the regional streamflow regimes classified as nival (snowmelt-dominated) (Bonsal et al, 2019). In boreal regions, the intensity and length of spring floods are controlled by the snow accumulation during winter and by the temperature of the melting period (Hardy et al, 1996;Snowball et al, 1999;Cockburn and Lamoureux, 2008;Ojala et al, 2013;Saarni et al, 2017).…”

“…The deficiency of observations led to the exploration of various natural archives for reconstructing past hydro-climatic conditions. Long hydro-climatic series based on natural proxies in the study region are rare and limited to tree-ring (Dinnis et al, 2019;Boucher et al, 2017;Begin et al, 2015;Naulier et al, 2015;Naulier et al, 2014;Nicault et al, 2014;Boucher et al, 2011;Begin et al, 2007;D'Arrigo et al, 2003) and pollen datasets (Viau et al, 2009). In this perspective, clastic varves formed and preserved in river-fed lakes have the potential to produce long paleohydrological series.…”

“…hydro-climatic conditions (Lamoureux, 2000;Lamoureux et al, 2006;Tomkins et al, 2010;Cuven et al, 2011;Kaufman et al, 2011;Schillereff et al, 2014;Amann et la., 2015;Heideman et al, 2015;Zolitschka et al, 2015;Saarni et al, 2016;Czymzik et al, 2018).…”

Current perspectives on the capabilities of high resolution XRF core scanners

“…The 2700-year record studied using microfacies analysis and µXRF scanning documents a significant correlation between detrital layer thickness and Ti as a terrigenous source indicator. Statistical links between detrital layer thickness and Ti to winter precipitation were established by calibration studies to produce a 2700 year-long annual scale reconstruction of snowfall (Czymzik et al, 2018).…”