Abstract
Holocene summer temperature reconstructions from northern Europe based on sedimentary pollen records suggest an onset of peak summer warmth around 9,000 years ago. However, pollen-based temperature reconstructions are largely driven by changes in the proportions of tree taxa, and thus the early-Holocene warming signal may be delayed due to the geographical disequilibrium between climate and tree populations. Here we show that quantitative summer-temperature estimates in northern Europe based on macrofossils of aquatic plants are in many cases ca. 2 °C warmer in the early Holocene (11,700–7,500 years ago) than reconstructions based on pollen data. When the lag in potential tree establishment becomes imperceptible in the mid-Holocene (7,500 years ago), the reconstructed temperatures converge at all study sites. We demonstrate that aquatic plant macrofossil records can provide additional and informative insights into early-Holocene temperature evolution in northernmost Europe and suggest further validation of early post-glacial climate development based on multi-proxy data syntheses.
Highlights
Holocene summer temperature reconstructions from northern Europe based on sedimentary pollen records suggest an onset of peak summer warmth around 9,000 years ago
Holocene pollen-based summer temperature reconstructions from northern Europe are predominantly driven by changes in the major arboreal pollen taxa[2], and inferred rises in temperature typically coincide with increases in certain tree-pollen taxa, such as spruce (Picea abies) in north-eastern European Russia[15], pine (Pinus sylvestris) in northern Fennoscandia[16] and deciduous trees (Alnus incana, Alnus glutinosa, Ulmus glabra, Corylus avellana, Tilia cordata and Quercus robur) in southern Fennoscandia and the Baltic countries[17] (Supplementary Fig. 1a)
Post-glacial tree migration-rate estimates have been revised in the light of emerging macrofossil evidence for the persistence of small tree populations in central and northern
Summary
Holocene summer temperature reconstructions from northern Europe based on sedimentary pollen records suggest an onset of peak summer warmth around 9,000 years ago. Most early Holocene temperature reconstructions are derived from fossil terrestrial–pollen assemblages that exclude local elements such as aquatic plants and assume that the pollen record reflects the regional vegetation and climate changes[2,3] They do not take into account the delay in tree range expansion in response to early Holocene climate warming due to the long population doubling times and relatively slow spread of trees[4]. In his classic work on the late-glacial flora of Denmark, Iversen[5] proposed that aquatic plants may provide a more accurate temporal record of the late-glacial and early post-glacial climate changes than trees due to their more rapid dispersal rates. Owing to their more rapid response times, aquatic plants may reflect actual temperature changes faster than pollen-based temperature reconstructions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
