{"id":13317,"date":"2011-06-09T16:56:49","date_gmt":"2011-06-09T23:56:49","guid":{"rendered":"http:\/\/blogs.kqed.org\/climatewatch\/?p=13317"},"modified":"2018-02-02T00:32:45","modified_gmt":"2018-02-02T00:32:45","slug":"forget-this-winter-western-snowpack-shrinking","status":"publish","type":"post","link":"https:\/\/ww2.kqed.org\/climatewatch\/2011\/06\/09\/forget-this-winter-western-snowpack-shrinking\/","title":{"rendered":"Forget this Winter: Western Snowpack Shrinking"},"content":{"rendered":"

By Alyson Kenward<\/a><\/strong><\/p>\n

A new study finds large losses of springtime snow cover in the West in recent years, raising concerns about water supplies.<\/strong><\/p>\n

\"\"
Spring snowpack in the West is an essential water resource, particularly in Southwestern states that are prone to summer drought, like California, Nevada, Arizona and New Mexico. (Credit:\u00a0Wolfgang Staudt on Flickr)<\/figcaption><\/figure>\n

This spring, from the Pacific Northwest and Sierra Nevada, to the Northern Rockies, western mountain ranges were more than just snow-capped \u2013 they were buried in the white stuff. In fact, many locations still have more spring snowpack<\/a> than has been seen in decades.<\/p>\n

Head south across the 40th<\/sup> parallel, however, and things are dramatically different. While there is still above average snow throughout the Sierra, a relatively snow-less winter and spring has left much of the Southwest in a drought<\/a> that has fostered record wildfires. Already local officials are worried there won\u2019t be enough water to get through the summer months ahead.<\/p>\n

This kind of contrast for the western spring snowpack is not unusual, though. It\u2019s completely normal, and it\u2019s exactly what climate scientists and meteorologists expect during years when the average weather pattern is influenced by La Ni\u00f1a<\/a>, a climate cycle associated with cooler than average water temperatures in the tropical Pacific Ocean.<\/p>\n

But while this north-south dichotomy turns out to be a regular feature of western climate, new research published today in the journal Science<\/em><\/a> shows that, when compared to typical snowfall during the past 1,000 years, snowpack patterns appear to be changing as average temperatures climb. Scientists say that as temperatures continue to rise, this reduced snowpack will lead to more frequent water shortages in increasingly thirsty western states.<\/p>\n

\u201cWe\u2019re talking about simultaneous snowpack decline in the western watershed that supports 70 million people,\u201d says U.S. Geological Survey<\/a> (USGS) climatologist Julio Betancourt<\/a>, who co-authored the new study. \u201cWe have to be concerned.\u201d<\/p>\n

For several years, scientists have observed<\/a> that spring snowpack all across the West \u2014 in both northern and southern areas \u2014 has been decreasing. But now, Betancourt and a group of other climate scientists have found that the recent decline is a departure from patterns of the past 1,000 years. As part of the study published in Science<\/em>, USGS ecologist Greg Pederson<\/a> investigated tree ring data<\/a> to learn how snowpack in the West, on either side of 40th<\/sup> parallel, changed from year-to-year and from decade-to-decade. Looking back over nearly a millennium, he found that when the north had high snowpack, the south typically experienced low snowpack, and vice versa.<\/p>\n

But Pederson and Betancourt noticed a change starting in the mid-1980\u2019s. On average, the amount of snow on the ground at the beginning of April each year was decreasing everywhere across the West. It\u2019s a trend that other scientists studying snowpack have pointed out. This has important consequences for water supplies for drinking water and agriculture, since many areas, including much of interior California, are dependent upon spring runoff for much of their water supplies.<\/p>\n

Betancourt says that as average spring temperatures have risen, the snowpack has begun to melt earlier in the year (not the case this year, with record cold weather locking in substantial amounts of snow in many western ranges). Moreover, he says that in many places, the warmer temperatures mean that precipitation falls more as rain than as snow. So while the actual amount of precipitation hasn\u2019t changed dramatically, the amount of rain has.<\/p>\n

\"\"<\/p>\n

\u201cSnowpack is the water resources of the West,\u201d says Greg McCabe<\/a>, a USGS hydrology expert who was not directly involved in the new study, \u201cand temperature has a dominant impact on the snowpack.\u201d If warming temperatures in the West cause the snowpack to decrease even more, McCabe says, or if the timing of the melt each spring changes, then summer water shortages could happen a lot more often.<\/p>\n

McCabe says the research provides valuable evidence about how snowpack has changed historically, and also how unusual the recent patterns appear to be.<\/p>\n

According to Pederson and Betancourt\u2019s findings, the way snowpack has changed in the past 30 years isn\u2019t entirely unprecedented. There were two brief periods in the mid-1300\u2019s and early 1400\u2019s where there was less snow built up throughout the West.<\/p>\n

\u201cAt both those other times in the past, we know it was warm then too,\u201d explains Betancourt.<\/p>\n

Now, however, climate scientists are predicting that average temperatures in the West are going to keep rising this century<\/a>, due in large part to the buildup of greenhouse gases in the atmosphere. Compared to the past, when snowfall returned to normal as temperatures dropped, researchers now expect that warmer spring weather could keep spring snowpack on the decline for years to come.<\/p>\n

\u201cWhat\u2019s happening in the spring for snow is critically important [for water availability] compared to what is happening in the dead of winter,\u201d says Betancourt.<\/p>\n

So what do the authors make of a year like this, which has brought frequent snowfall to the Sierra, even into June?<\/p>\n

\u201cThere isn\u2019t anything that has happened this year that isn\u2019t consistent with what our new findings are,\u201d says Pederson. Even as average temperatures increase in the coming years, there will still be cool years where above average snowpack builds up in parts of the West, particularly during La Ni\u00f1a years. \u201cBut these years will tend to be weather noise over top of the larger climate changes we will see over many years,\u201d he says.<\/p>\n

NPR’s Richard Harris interviews Pederson in this story<\/a> for <\/em>Morning Edition.<\/em><\/p>\n

A version of this post also appears at Climate Central<\/a>, a content partner of KQED <\/em>Climate Watch.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

A new study finds unusually large losses of springtime snow cover in the West in recent years, raising concerns about water supplies. <\/p>\n","protected":false},"author":11421,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[6,7],"tags":[172,251,511,524,527,581,654],"coauthors":[],"series":[],"affiliates":[],"programs":[],"collections":[],"interests":[],"class_list":["post-13317","post","type-post","status-publish","format-standard","hentry","category-thescience","category-water","tag-drought","tag-global-warming","tag-sierra-nevada","tag-snow","tag-snowpack","tag-temperature","tag-water"],"acf":{"template_type":"standard","featured_image_type":"standard","is_audio_post":false},"yoast_head":"\nForget this Winter: Western Snowpack Shrinking | Climate Watch<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, 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