A high-resolution multi-proxy lake record of Holocene environmental change in southern Iceland

Vestra Gíslholtsvatn, a non-glacial lake in southern Iceland, provides a continuous high-resolution multi-proxy paleoenvironmental record spanning more than 10 ka. It is characterized by an interplay between volcanic and climatic controls on the lake sediment environmental proxies. Initial lake ontogeny was disrupted by deposition of the Saksunarvatn tephra (~10.3 ka) followed by unusually slow ontogeny for 2 ka. Principal component analysis defines three climate zones between 8 and 1 ka. Quasi-stabilization and warm summer proxies between ~8 and 5.7 ka define Holocene Thermal Maximum conditions. A subtle shift to cooler summers between ~5.7 and ~4.2 ka is interpreted as early Neoglaciation, intensifying after 4.2 ka. Following settlement of Iceland (~1.1 ka) anthropogenic signals overprint the climate record. Throughout the record short-term variability is attributed to tephra fall events in the catchment from nearby explosive volcanism, whereas centennial- and millennial-scale changes are attributed to climate. When compared with other Icelandic lakes, environmental proxies from Vestra Gíslholtsvatn indicate less variability albeit similar timing of environmental change, suggesting a relatively stable flow of the Irminger Current along the south coast of Iceland compared with a more variable flow of warm Atlantic surface water along the western and northern coasts of Iceland after 8 ka.