Warmth-Demanding Species, Glacier Melt Measurements Affirm Early Holocene Svalbard Was 7°C Warmer Than Now

Using biomarker evidence (for example, the Early Holocene presence of sea creatures unable to survive below fixed warmth thresholds) and glacier melt extent measurements (for example, sea shells buried 6 km inside a glacier), scientists have been colloborating on a growing consensus that much of Arctic Svalbard was about 7°C warmer than today during the Early Holocene, when CO2 concentrations lingered near 260 ppm.

1. Farnsworth et al., 2020: “peak Holocene temperatures reaching 7 °C warmer than today, c. 10 ka BP” … “shells sampled from within a thrusted debris band located 6 km inside the modern ice margin of a major outlet glacier date to 10.3 ±0.49 ka BP”

Image Source: Farnsworth et al., 2020

2. Leopold et al., 2019: “the summer SSTs today around Svalbard are some 5-8°C lower than during the thermal peak of the Early Holocene”

Image Source: Leopold et al., 2019

3. van der Bilt et al., 2019: “Warmth was greatest around 10 ka BP, when temperatures were up to ~7 °C higher than present in response to high radiative forcing”

Image Source: van der Bilt et al., 2019

4. Łacka et al., 2019: “At approximately 6400 cal yr BP, the SST in Storfjordrenna reached a peak of almost 13 °C” (about 10°C warmer than the 2015 measured temperatures of about 2-4°C) … “after 10,000 cal yr BP, the glaciers in western Svalbard were even smaller than those of the present day” … “Sea ice-free conditions remained during most of the mid-Holocene”

Image Source: Łacka et al., 2019

5. Beierlein et al., 2015: “the maximum BWT [bottom water temperature] amounts to 15.2°C, which is 8-10°C higher than maximum summer BWTs in this region”