Stable water isotope climate archives in springs from the Olympic Mountains,Washington

The ¹⁸O and ²H (HDO) compositions are summarized for sampled springs (n = 81) within the Elwha watershed (≈692 km²) on the northern Olympic Peninsula. Samples, collected during 2001–2009, of springs (n = 158), precipitation (n = 520), streams (n = 176), and firn (n = 3) assisted the determinations for meteoric composition of recharge waters. The local mean water line (LMWL) is defined as δ²H = 8.2δ¹⁸O − 9.3 for the watershed. Recharge history is surmised from groundwater ages ranging from 5 ± 3 years (apparent ⁸⁵Kr) to 9,490 ± 420 ¹⁴C cal years BP. About 56% of the springs were recharged over the last 1,000 years while 13% of springs were recharged over 5,000 years ago. Spring HDO values fluctuate between −11.8 to −15.6‰ δ¹⁸O and −90.9 to −119.4‰ δ²H. Deuterium excess values predominate around 4–6‰. The HDO proxy records from springs suggest a pronounced paleoclimate shift in air masses near 5,000 year BP on the Peninsula.