Fig. 4: Distribution of breakpoints of Gulf of Maine temperature and oxygen isotope time series.

a Breakpoint years calculated from segmented regression analysis of single and fully forced simulations as well as the oxygen isotope record over the period of overlap between the records (1694–2005). The histogram plots the breakpoint year of ensemble members of the fully-forced simulations, with a bin-size of ~60 years. The oxygen isotope record breakpoint (green vertical line) is 1875 and calculated over the full record (1694–2013). The calculated breakpoint for each single forced ensemble member are represented by colored points on the x-axis.Years of ensemble member mean breakpoints (for both full forcing and single forcing simulations) are represented as vertical lines. b As in a but segmented regression analysis is performed over the entire millennium period (1000–2005). Bin size is still ~60 years. Oxygen isotope breakpoint included for reference. SSI spectral solar irradiance, VOLC volcanic, GHG greenhouse gas. Breakpoint years calculated from the climate model simulations are the result of segmented regression analysis of annual temperatures at 35 m depth in the Gulf of Maine for individual ensemble members (colored points; both full forcing and single forcing), the ensemble member mean (vertical lines; both full forcing and single forcing).