Svalbard temperatures were both warmer & colder than today in the Early Holocen: Temperatures were up to ~7C higher than now in response to high radiative forcing & intensified ocean heat advection

Early Holocene temperature oscillations exceed amplitude of observed and projected warming in Svalbard lakes. Willem G.M. van der Bilt  William J. D`Andrea  Johannes P. Werner  Jostein Bakke. Geophysical Research Letters, December 3 2019. https://doi.org/10.1029/2019GL084384

Abstract: Arctic climate is uniquely sensitive to on‐going warming. The feedbacks that drive this amplified response remain insufficiently quantified and misrepresented in model scenarios of future warming. Comparison with paleotemperature reconstructions from past warm intervals can close this gap. The Early Holocene (11.7‐8.2 ka BP) is an important target because Arctic temperatures were warmer than today. This study presents centennially resolved summer temperature reconstructions from three Svalbard lakes. We show that Early Holocene temperatures fluctuated between the coldest and warmest extremes of the past 12 ka, exceeding the range of instrumental observations and future projections. Peak warmth occurred ~10 ka BP, with temperatures 7°C warmer than today due to high radiative forcing and intensified inflow of warm Atlantic waters. Between 9.5‐8 ka BP, temperatures dropped in response to freshwater fluxes from melting ice. Facing similar mechanisms, our findings may provide insight into the near‐future response of Arctic climate.

4 Conclusions
Alkenone (𝑈37 𝐾) ) data show that Svalbard experienced summer temperatures both warmer and colder than today during the Early Holocene. Warmth was greatest around 10 ka BP, when temperatures were up to ~7 °C higher than present in response to high radiative forcing and intensified ocean heat advection. In agreement with a growing body of recent work (e.g.
Lecavalier et al., 2017; McFarlin et al., 2018), these findings indicate an earlier and warmer
Holocene Optimum in the High Arctic then previously suggested. Moreover, comparison with
model output shows that the amplitude of warming was on par with 21st century emission
scenarios, but that temperatures rose much slower than today. A denser and more evenly spread distribution of similar high-resolution reconstructions is needed to ascertain if this signal is representative for the wider region. Between 10-8 ka BP, temperatures declined in response to freshwater input into the North Atlantic from melting ice sheets. The sensitivity of regional climate to freshwater forcing is of relevance for a future Arctic, which will likely be impacted by increased melting of the Greenland ice sheet and enhanced runoff as the hydrological cycle intensifies (Bintanja & Selten, 2014; Shepherd et al., 2012).