Arctic and sub-Arctic lake water δ2H and δ18O along a coastal-inland transect: Implications for interpreting water isotope proxy records

•δ2H and δ18O of 135 lakes along transect from North Atlantic Ocean to Bothnian Bay.•All lakes are sensitive to distillation processes during moisture transport.•Inflow isotopic composition and evaporation are equally important for inland lakes.•Interannual variability likely reflects seasonal atmospheric circulation changes.•Variable sensitivity to inflow and evaporation needs consideration in proxy studies.