Stable isotopes of oxygen and hydrogen in the Truckee River–Pyramid Lake surface‐water column. 1. Data analysis and extraction of paleoclimatic information

Abstract

The δ18O content of streamflow discharge entering Pyramid Lake is a simple mixture of isotopically enriched Lake Tahoe discharge and isotopically depleted snowmelt. The δ18O value of Pyramid Lake water varies continuously, as isotopically depleted water evaporates from the epilimnion and isotopically depleted water enters the lake as streamflow discharge and on‐lake precipitation. In a normal water year, the δ18O of Pyramid Lake surface water varies seasonally because the components of the hydrologic balance in the Pyramid Lake system are seasonally shifted. The problem of isotopic and thermal heterogeneity can be minimized by analyzing carbonates that integrate the annual variance in δ18O, form in an environment in which temperature is relatively invariant, and are not subject to recrystallization after deposition.