Geology topics

C.A. Woodhouse

Publications and source records attributed to C.A. Woodhouse.

3 recordsLinked to original sources

USGS2017

An 1800-yr record of decadal-scale hydroclimatic variability in the upper Arkansas River basin from bristlecone pine

Bristlecone pine trees are exceptionally long-lived, and with the incorporation of remnant material have been used to construct multi-millennial length ring-width chronologies. These chronologies can provide valuable information about past temperature and moisture variability. In this study, we outline a method to build a moisture-sensitive bristlecone chronology and assess the robustness and consistency of this sensitivity over the past 1200. yr using new reconstructions of Arkansas River flow (AD 1275-2002 and 1577-2002) and the summer Palmer Drought Sensitivity Index. The chronology, a composite built from parts of three collections in the central Rocky Mountains, is a proxy for decadal-scale moisture variability for the past 18 centuries. Since the sample size is small in some portions of the time series, the chronology should be considered preliminary; the timing and duration of drought events are likely the most robust characteristics. This chronology suggests that the region experienced increased aridity during the medieval period, as did much of western North America, but that the timing and duration of drought episodes within this period were somewhat different from those in other western locations, such as the upper Colorado River basin. ?? 2010 University of Washington.

Quaternary Research↗

USGS2011

Climatic controls on the snowmelt hydrology of the northern Rocky Mountains

The northern Rocky Mountains (NRMs) are a critical headwaters region with the majority of water resources originating from mountain snowpack. Observations showing declines in western U.S. snowpack have implications for water resources and biophysical processes in high-mountain environments. This study investigates oceanic and atmospheric controls underlying changes in timing, variability, and trends documented across the entire hydroclimatic-monitoring system within critical NRM watersheds. Analyses were conducted using records from 25 snow telemetry (SNOTEL) stations, 148 1 April snow course records, stream gauge records from 14 relatively unimpaired rivers, and 37 valley meteorological stations. Over the past four decades, midelevation SNOTEL records show a tendency toward decreased snowpack with peak snow water equivalent (SWE) arriving and melting out earlier. Temperature records show significant seasonal and annual decreases in the number of frost days (days ≤0°C) and changes in spring minimum temperatures that correspond with atmospheric circulation changes and surface–albedo feedbacks in March and April. Warmer spring temperatures coupled with increases in mean and variance of spring precipitation correspond strongly to earlier snowmeltout, an increased number of snow-free days, and observed changes in streamflow timing and discharge. The majority of the variability in peak and total annual snowpack and streamflow, however, is explained by season-dependent interannual-to-interdecadal changes in atmospheric circulation associated with Pacific Ocean sea surface temperatures. Over recent decades, increased spring precipitation appears to be buffering NRM total annual streamflow from what would otherwise be greater snow-related declines in hydrologic yield. Results have important implications for ecosystems, water resources, and long-lead-forecasting capabilities.

Idaho, Montana↗

USGS2011

The unusual nature of recent snowpack declines in the North American cordillera

In western North America, snowpack has decl in ed in recent decades, and fur the r losses are projected through the 21st century. Here, we evaluate the uniqueness of recent declines us in g snowpack reconstructions from 66 tree-r in g chronologies in key run of f-generat in g areas of the Colorado, Columbia, and Missouri River dra in ages. Over the past millennium, late 20th century snowpack reductions are almost unprecedented in magnitude across the north ern Rocky Mounta in s and in the ir north -south synchrony across the cordillera . Both the snowpack declines and the ir synchrony result from unparalleled spr in gtime warm in g that is due to positive re in forcement of the anthropogenic warm in g by decadal variability. The in creas in g role of warm in g on large-scale snowpack variability and trends foreshadows fundamental impacts on streamflow and water supplies across the western United States.

Science↗