Search - NW Climate Science Digest

Use this page to search climate science digests beginning in 2015.

Digests from 2013-2014 are archived here.

Digest Articles

Aquatic Resources, Stream Flow, Hydrology in the Western U.S.

Estimates of twenty-first-century flood risk in the Pacific Northwest based on regional climate model simulations

Eric P. Salathé Jr., Alan F. Hamlet, Clifford F. Mass, Se-Yeun Lee, Matt Stumbaugh, and Richard Steed, 2014: Estimates of Twenty-First-Century Flood Risk in the Pacific Northwest Based on Regional Climate Model Simulations. J. Hydrometeor, 15, 1881–1899. doi:

Results from a regional climate model simulation show substantial increases in future flood risk (2040–69) in many Pacific Northwest river basins in the early fall. Two primary causes are identified: 1) more extreme and earlier storms and 2) warming temperatures that shift precipitation from snow to rain dominance over regional terrain. The simulations also show a wide range of uncertainty among different basins stemming from localized storm characteristics.

Commentary on Heightened Risk of Drought due to Climate Change

Mann, M.E. and P.H. Gleick 2015. Climate change and California drought in the 21st century. PNAS 112, 13, 3858-3859. doi: 10.1073/pnas.1503667112

In this commentary piece, Pacific Institute Director Peter Gleick and Pennsylvania State University Meteorologist Michael Mann discuss the state of current literature on drought and climate science. They discuss a new study published in PNAS by Diffenbaugh et al., which shows accumulating evidence that climate change is influencing the frequency, magnitude and duration of drought in California. An increasing number of dry years along with warm years raise the risk of drought, despite the lack of a strong trend in precipitation. These results point to the significance of warming temperatures to changing the availability of water and increasing drought intensity. It is important to note, however, as the authors do, that this is not uncontested. A number of recent studies (some of which focused on a lack of trend in precipitation) concluded that a link between ocean temperatures and drought could not yet be established. Part of the debate, however, has occurred because there are many ways in which drought can be defined. A drought can be meteorological, hydrological, agricultural, and/or socioeconomic. Other parts of the debate stem from attribution. Some studies argue that low levels of precipitation cannot be tied to climate change, while others argue that while this may be true, the low levels of precipitation are caused by an unusually strong ‘atmospheric ridge’ in the Western United States, which was most likely stronger due to climate change.

Calculating the role of lakes in global warming

Biologist Kevin Rose from the Rensselaer Polytechnic Institute and colleagues are undergoing a large-scale study examining the potential impacts of rising temperatures on the carbon cycle of lakes. Lakes are a major part of the carbon cycle. The amount of carbon dioxide and methane that a lake emits depends on temperature, making Rose’s research question significant for understanding how carbon emission from lakes will change with future warming.  Funded by the National Science Foundation, the researchers will project future weather conditions for 2000 lakes over the next 90 years. The simulations will include changes in weather, water temperature and carbon and methane emissions. The authors will then combine this data with known physical, chemical and biological characteristics of the individual lakes in order to produce a large-scale dataset of predicted changes to lake thermal characteristics such as the temperature profile, depth of temperature stratification, and ice cover. Such thermal features of these lakes will lead to the determination of lakes as either a source or sink of carbon under future warming conditions.

Predicting Climate Change Impacts on Aquatic Ecosystems across the Pacific Northwest

In case you missed it last December, USGS ecologist, Clint Muhlfeld’s, webinar about climate impacts to NW trout and salmon is now available online.

Depletion and response of deep groundwater to climate-induced pumping variability

Russo, T.A. & Lall, U. 2017. Depletion and response of deep groundwater to climate-induced pumping variability Nature Geoscience 10, 105–108. doi:10.1038/ngeo2883

Widespread groundwater level declines have occurred in the U.S. over recent decades, even in regions not typically considered water stressed, such as areas of the Northwest. This loss of water storage reflects extraction rates that exceed natural recharge and capture. In this article the authors explore recent changes in the groundwater levels of deep aquifers from wells across the U.S., and their relation to indices of climate variability and annual precipitation. They found that groundwater level changes corresponded to selected global climate variations. Although climate-induced variations of deep aquifer natural recharge are thought to have multi-year time lags, they found that deep groundwater levels respond to climate over timescales of less than one year. In irrigated areas, the annual response to local precipitation in the deepest wells may reflect climate-induced pumping variability. Understanding how the human response to drought leads to deep groundwater changes is critical for managing the impacts of climate variability on the nation’s water resources.

Assessing the Effectiveness of Stream Restoration Monitoring in the Northwest

Stephen Bennett, George Pess, Nicolaas Bouwes, Phil Roni, Robert E. Bilby, Sean Gallagher, Jim Ruzycki, Thomas Buehrens, Kirk Krueger, William Ehinger, Joseph Anderson,Chris Jordan, Brett Bowersox & Correigh Greene. 2016. Progress and Challenges of Testing the Effectiveness of Stream Restoration in the Pacific Northwest Using Intensively Monitored Watersheds. Fisheries. 41(2):92-103.

The Pacific Northwest, due to its large populations of endangered anadromous fish populations (salmon and steelhead), has seen major efforts toward implementing stream restoration. While these efforts are seen as ecologically sound, little research has been done to understand the relationship between freshwater habitat improvement and increased fish populations. Therefore, 17 watershed projects have been implemented to test the validity of this relationship. In this recently published article, Bennett et al. (2016) assessed the scope and status of these 17 projects and reported current challenges and suggestions for improving experimental designs that fit into an adaptive management framework. Based on their assessment, the authors confirmed that intensive monitoring of watersheds is a sound approach for measuring the success of stream restoration, though they found funding and coordination between participants and stakeholders to be significant challenges.

Snowmelt rate dictates streamflow

Barnhart, T. B., N. P. Molotch, B. Livneh, A. A. Harpold, J. F. Knowles, and D. Schneider. 2016. Snowmelt rate dictates streamflow, Geophys. Res. Lett., 43, 8006–8016, doi:10.1002/2016GL069690.

A new study from the University of Colorado looked at the relationship between snowmelt rate and streamflow generation using the Budyko framework, a mechanism used to compare streamflow and evaporative partitioning of different watersheds for a given amount of available energy and precipitation. The authors quantified an ensemble of “Budyko streamflow anomalies” and correlated them with simulated baseflow efficiency and simulated snowmelt rate. These findings support a possible streamflow generation mechanism where greater snowmelt rates increase subsurface flow. Significance of the mechanism detected in this study includes the possibility of decreased streamflow production under slower snowmelt conditions.

Climate warming contributes to native and invasive trout hybridization

Nature Clim. Change, 2014/07/, Vol 4, Issue 7, pp 620- 624,

Results from a study conducted by Dr. Clint Muhlfeld, US Geological Survey, with funding support from the Great Northern LCC, was recently published in the journal Nature Climate Change. The paper reports that rapid climate warming contributes to hybridization between native and invasive trout species. Muhlfeld and his collaborators examined long-term genetic monitoring data with high-resolution climate and stream temperature predictions. Their findings indicate that invasive hybridization could result in genomic extinction for many native species. 

Impacts of climate change on groundwater resources in Washington state

Pitz, Charles. 2016. Predicted Impacts of Climate Change on Groundwater Resources of Washington State. Washington State Department of Ecology. Publication No. 16-03-006

The Washington State Department of Ecology recently released a synthesis report on the climate-induced impacts of groundwater resources in the state. Author and hydrogeologist Charles Pitz evaluated and recommended preferred methods for assessing climate change impacts on groundwater storage. The author then described the current understanding of climate change impacts on five different groundwater characteristics: groundwater recharge/storage, surface water interactions/baseflow discharge, quality, temperature, and the impacts of sea-level rise. The report concludes with recommendations for Washington State water resource managers on improving protections against groundwater storage loss through increased and better statewide monitoring and assessing.

Climate change darkening Seattle’s water forecast

This summer’s drought is changing the long-term outlook for Seattle’s water forecast. Seattle Public Utilities (SPU) models of future water utilities show that Seattle is looking at a reduced ‘firm yield’ of 30% on average through 2050. Firm yield describes the amount of water that can be reliably delivered. Prior to this summer, SPU officials thought that there would be no major water-supply problems before 2060. But now things look different. Director of SPU, Ray Hoffman, stated, “’This year, as tough as it is, is a real revelation for what the future might look like.’” SPU is in the process of thinking through possible adaptation options that might mitigate the severity of future droughts. Alex Chen, SPU’s director of water planning, is exploring various ideas for maximizing performance, including an increase of water storage in the Cedar and Tolt reservoirs or reusage of precipitation falling on Seattle. Chen even mentioned desalinization.