Figure 1: Arctica islandica47 results . Clumped isotope results are aggregated by specimen or multi-specimen sample (round symbols; see Table 1 ). Vertical lines represent 95% CL and number indicate sample size. Data is color-coded per temperature treatment (1°C, 3°C, 15°C and 18°C), with bold error bars indicating 95% CL. The grey error bar at 6°C highlights A. islandica data from Bernasconi et al. (2018; recalculated to I-CDES). Solid and dashed black lines show calibrations by Anderson et al. (2021) and Meinicke et al. (2020; projected on I-CDES scale; Meinicke et al., 2021), respectively. Grey solid and dashed lines represent, respectively, the theoretical calcite (“cc”) and aragonite (“ar”) temperature dependencies from Guo et al. (2009; projected on the I-CDES scale, see S1 ). The horizontal axis is scaled to\(\frac{10^{6}}{T^{2}}\), with T in K, to show the assumed linear relationship with the clumped isotope value.