Fig. 3

Co-isotope plot of local GNIP (Global Network of Isotopes in Precipitation) data and δ_{pore ice}. a Mayo GNIP data (grey circles) used to constrain the Local Meteoric Water Line (LMWL; excluding any leverage points marked with a square and likely evaporation-enriched data points marked with red crosses) and the composite DHP174 (Dempster Highway Peatland, near 174 km marker) δ_{pore ice} record (δ_seawater-corrected—as in Fig. 2d, e); δ_{pore ice} data points are colour coded by age classes >9.2 ka BP (blue circles), 9.2–5 ka BP (yellow circles) and <5  ka BP (red circles); b enlarged inset (as shown in subplot ‘a’) with separate regression lines for the LMWL (black), and early Holocene (>9.2 ka cal BP; blue) and late Holocene (<5 ka cal BP; red) δ_{pore ice}