Fig. 4.

Subannual δ¹⁸O_shell-based reconstructed temperature over five years (2005–2009) from three shells (gray lines) with mean across all samples (black) and instrumental temperature measurements from 100 m depth averaged between stations FX3 and FX4 from 2002 to 2015 (blue). Sampling was performed using a micromill (upper) and repeated by hand using a Dremel tool (lower). The dashed lines in the lower plot represent samples where shell was milled to include the material encompassing the increment line at the boundary of the annual growth increment (hand sampling). This is in contrast to sampling shell material deposited after (and not including) the increment line and up to the boundary (and not including) the following increment line (upper, micromill). The combined uncertainty (1.47 °C) is derived from uncertainty estimates related to instrumental precision (0.52 °C; 2 sigma standard deviation) and the Grossman and Ku (1986) temperature equation (1.37 °C; mean squared error). (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)