Data from: Last Glacial Maximum environmental conditions at Andøya, northern Norway; evidence for a northern ice-edge ecological “hotspot”

Andøya on the NW coast of Norway is a key site for understanding the Last
Glacial Maximum (LGM) in northern Europe. Controversy has arisen
concerning the local conditions, especially about the timing and extent of
local glacial cover, maximum July temperatures and whether pine and/or
spruce could have grown there. We reviewed all existing data and add newly
analysed ancient sedimentary DNA, pollen, macrofossils, geochemistry and
stable isotopes from three lake sediment cores from Øvre Æråsvatnet. A
total of 23 new dates and age-depth modelling suggests the lake has been
ice-free since GI2 (<22.8 k cal. BP) and possibly GS3 (<27.4
k cal. BP). Pinus and Picea sedimentary ancient DNA (sedaDNA) was found in
all three cores but at such low frequencies that it could not be
distinguished from background contamination. LGM samples have an
exceptionally high organic matter content, with isotopic values indicating
that carbon and nitrogen derives from a marine source. Along with finds of
bones of the little auk (Alle alle), this indicates that the lake received
guano from an adjacent bird colony. DNA, pollen and macrofossil
assemblages were dominated by Poaceae, Brassicaceae and Papaver, but
scattered occurrence of species currently restricted to the Low Arctic
Tundra Zone (July temperature of 8-9°C) such as Apiaceae (DNA, 8-9°C), and
Alchemilla alpina (macrofossil, 8-9°C) were also recorded. The review
showed 94 recorded vascular plant taxa, of which 38% have a northern limit
in Shrub Tundra or more southern vegetation zones. This unusual assemblage
likely stems from a combination of proximity to ice-free water in summer,
geographical isolation linked with stochastic long- distance dispersal
events, and the presence of bird-fertilized habitats. The environmental
reconstruction based on all records from the area does not preclude local
growth of tree species, as the local climate combined with high nutrient
input may have led to periodically suitable environmental ‘hotspot’
conditions.