Reconstruction of Holocene hydroclimate shifts in the Canadian Rocky Mountains using stable oxygen isotopes from Princess Lake, Jasper National Park

Paleoclimate studies documenting changes in regional water balance (precipitation – evaporation) over long time periods are necessary to place the rapid, anthropogenically-driven climate changes occurring today into a longer perspective. One way to investigate regional paleohydrology is through the measurement of oxygen isotopes preserved in authigenic carbonates precipitated from lake water and archived in lakebed deposits, thereby capturing the water chemistry at the time of formation. In open-basin lakes, water rapidly flows through the system, similar to a river, and are considered faithful recorders of precipitation 18O (meteoric water). Alternatively, closed-basin lakes which have no permanent outflows are more sensitive to evaporative enrichment of the 18O signal. Lakes that fall in between closed and open reflect a balance between precipitation and evaporation and often reveal subtle paleoclimate shifts that are missed in other lakes. Here, we present a carbonate isotope record from Princess Lake, a semi-closed basin lake located in Jasper National Park, Alberta, Canada. Modern water isotope data and field observations indicate that Princess Lake’s hydrology is highly sensitive to precipitation amount with a single outflow that floods and results in more depleted 18O and 2H isotope values following years of high precipitation. The Princess Lake sediment record provides a robust, high-resolution dataset of the last 4.1 thousand years (ka). For the majority of the record, Princess Lake 18O values are similar to that of Lime Lake, a known open-basin lake in the region. From 3.5 - 2.6 ka and 2.2 - 1.7 ka, Princess 18O values increase by 5.0 ‰ and reach values similar to those of nearby Celestine Lake, a known closed-basin lake. These periods of isotopic enrichment provide evidence for sustained droughts during the late Holocene that were characterized by an abrupt onset. The cyclic sustained droughts are likely the result of short timescale shifts in Pacific circulation patterns, which are modulated by the higher insolation in the earlier half of this record. The unique hydrologic sensitivity of Princess Lake provides a novel record of late Holocene megadroughts in the Canadian Rocky Mountains that have been undetected by previous studies.