Sediment microfacies, geochemical μ‐XRF and X‐ray density analyses were
conducted on varved sediments from Lake Kortejärvi
(eastern Finland) covering the last 2700 years. The varves
comprise couplets of detrital
and organic sub‐layers 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 snow‐melt
layer thickness tend to be connected
with a more positive phase of the NAO and, consequently, warmer
winters. In contrast, distinct centennial intervals of
thicker snow‐melt layers from −40 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.