Date of Thesis

Spring 2026

Description

Holocene temperature records provide context for current climate changes and past climate drivers, which can help anticipate potential future changes. Such records are critical in the rapidly warming Arctic, and when paired with vegetation and fire histories, allow for a deeper understanding of how humans influence their environment over time.

The Lofoten Islands in northern Norway lie near the northern limit of cereal cultivation and have a long history of human settlement, yet they lack Holocene terrestrial temperature reconstructions. Here, we present a 7,600-year temperature record from a sediment core collected from Lauvdalsvatnet (68°14′07′′ N, 13°54′22′′ E; 53 m a.s.l.), a freshwater lake on Vestvågøy in the Lofoten Islands. The site is near Borg, a Viking-age cultural hub with evidence for agricultural activity dating back to the Bronze Age (Johansen et al., 1990). As a region lacking Holocene terrestrial temperature records but with a long history of human settlement, this study helps assess how humans and climate have shaped this environment.

The Lauvdalsvatnet temperature record was derived using lacustrine alkenones, lipid biomarkers produced by haptophyte algae in Arctic lake surface waters, preserved in a lake sediment core. An age-depth model was constructed using radiocarbon dates of plant macrofossils (Topness et al., 2023). With a published alkenone calibration local to the Lofoten (D’Andrea et al., 2016), we determined past lake water temperature based on the degree of alkenone unsaturation. The results reveal an average lake water temperature of 6.0°C over the past 7,600 years. The highest inferred temperatures occurred around ~6,900 and ~6,200 cal yr BP, with peaks of 8.7°C and 9.7°C, respectively. A cold period is documented to be ~3,900 cal yr BP, with a temperature of 3.9°C. Overall, the record reveals a long-term cooling trend, over the past 6,000 years. Unpublished pollen data from the same core show an increase in Picea (spruce) after 4,000 cal yr BP, consistent with a transition to cooler conditions. Poaceae (grasses) increased after 3,000 cal yr BP and peaked near present. Hordeum (barley) appears ~3,500 cal yr BP, marking the onset of agriculture. Polycyclic aromatic hydrocarbons (PAHs), biomarkers produced from biomass burning, peak at 800 cal yr BP (Viking Age) and ~200 cal yr BP, reflecting intensified settlement and anthropogenic landscape modification (Topness et al., 2023).

These results indicate that early-mid Holocene temperature variability in northern Norway was primarily driven by orbitally forced insolation changes, with additional centennial–millennial variability linked to ocean–atmosphere dynamics. The late Holocene shows increasing evidence of human influence on fire regimes and vegetation, indicating a shift toward anthropogenically modified landscapes. The temperature, vegetation, and fire records reflect complex human-climate-landscape interactions during the Late Holocene.

Keywords

Holocene, Alkenones, Arctic, Lake, Human-climate

Access Type

Honors Thesis (Bucknell Access Only)

Degree Type

Bachelor of Science

Major

Geology & Environmental Geosciences

First Advisor

Lorelei Curtin

Second Advisor

Ellen Herman

Third Advisor

Adam Mair

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