Climate Fact: Crater Lake Water Levels and PDO
About 7,700 years ago, a volcanic eruption 42 times more powerful than the 1980 Mt. St. Helens event happened at Mt. Mazama in the southern Oregon Cascade Mountains. The top 5,000 feet of the mountain collapsed soon afterwards, leaving behind a huge caldera, or crater, which has since filled with about 4.6 trillion gallons of water that make up America’s deepest lake – Crater Lake. Crater has been called “the world’s largest rain gauge,” as the lake’s surface comprises about 78.5 percent of its watershed and there are no streams flowing into or out of the lake. Thus, trends in Crater Lake’s water levels provide an effective proxy for local temperature and precipitation trends. The historical record shows that these lake levels are influenced by the behavior of the Pacific Decadal Oscillation (PDO), or the periodic shift in heat distribution in the Pacific Ocean. During negative (wet and cool) phases, the mid-latitude storm track that brings moisture to the Pacific Northwest tends to consistently travel over southern Oregon. During positive (warm and dry) phases, the storm track moves and southern Oregon does not receive as much precipitation. Lake levels reached 300 year lows during the late 1980′s and early 1990′s, after years of a strongly positive PDO.
Seasons: Winter, Spring, Summer, Fall
Sources: Peterson, DL et al. “Detecting Long-Term Hydrological Patterns at Crater Lake, Oregon.” Northwest Science 73 (1999): 121-130 and Uhler, John W. “Crater Lake National Park Information Page.” Online Posting, 2007. 4 September 2008
