Historic comparison and 2015 Spring Outlook - What can

Tuesday, April 14, 2015 Webinar Moderated by: Tina Buxbaum UAF is an AA/EO employer and educa>onal ins>tu>on. Photo courtesy of Ma/ Druckenmiller Welcome to the ACCAP’S Alaska Climate Webinar Series Welcome Alaska River Breakup Historic Comparison & 2015 Spring Outlook What we can expect? Crane Johnson & Rick Thoman, Na>onal Weather Service Outline •  Overview of the breakup process •  Recap of 2014 Alaska Breakup •  Current 2015 condi>ons •  Climate Outlook •  A look at trends: past, present and future •  Spring 2015 Breakup Outlook Types of Breakup Process Most Breakups are a Blend
Dynamic breakup Thermal breakup •  Ice remains hard and resistant to breaking up •  Ice moves when pushed by ice from upstream •  Ice jams form that can cause upstream flooding •  Extreme cases are Kenai River in January 1969 and January 2007 and Yukon River in May 2009 and 2013. •  Ice becomes very ro/en (candled) before ice from upstream arrives •  Ro/en ice is weak and has less resistance to breaking into very small pieces •  No significant ice jams form •  Extreme case would occur with very li/le snow melt inflow and warm sunny weather to rot the ice Breakup Overview – 2 Types The transi>on from an ice covered river to ice-­‐free open water Thermal Breakup Overview The transi>on from an ice covered river to ice-­‐free open water Dynamic or Mechanical When is breakup? “The breakup front is the interface between sta>onary and moving ice sheets……” Flow DirecHon When is breakup? Or….. Recap of 2014 – at this point •  Spring snow condi>ons –  Snow depth in Southcentral and Western Alaska were well below normal for the beginning of April –  Snow depth in the Canadian Yukon, Upper Yukon, Tanana River and North Slope drainages was near or slightly above normal •  Spring ice thickness –  were normal to below normal for most of the state •  Weather outlook in mid to late April? –  increased chance of above normal temperatures through April 30 Snow Pack on April 1, 2014 Ice Thickness Percent of Normal 2014 Ice thicknesses at the beginning of March were generally below normal with the excep>on of Eagle. April values show a similar trend with fewer sta>ons repor>ng. 2014 Spring Temperatures April CPC Climate Outlooks April, May, June 2014 Ini>al Outlook Low to Low-­‐Moderate 2014 Breakup Summary •  Lower Kuskokwim and Yukon River experienced a thermal breakup and were ice free earlier than normal. •  Upper rivers experience mild dynamic breakups with only minor flooding observed. •  Two notable ice jams on the Kuskokwim River (1 warning and 1 watch issued) –  WARNING: Ice Jam downstream from Red Devil causes water levels to rise 6 to 8 feet to near bankfull levels and causes nuisance flooding (Upstream threat) –  WATCH: Ice Jam upstream from Tuluksak causes river level to rise above bank full levels (Downstream threat) •  One notable ice jam on the Yukon River (advisory issued) –  ADVISORY: Ice jam upstream of Circle caused minor flooding Red Devil 2014 Ice Jam Last Minute Caribou Crossing So what about this year? •  Ice thicknesses around the state are below normal in the Southwest and normal to above normal in the interior and upper Yukon •  Snow depths in Southcentral and Western Alaska are well below normal for the beginning of April •  Snow depth in the Canadian Yukon, Upper Yukon, Tanana River and North Slope drainages is near or slightly above normal •  Weather is the key. CPC outlook for April (one month) indicates more likely above normal temperatures for Southcentral and equal chances for above or below normal for the Northern half of the state. 2015 Winter Anomalies 2015 Ice Condi>ons •  Limited direct observa>ons – generally below average on the Kuskokwim and average to above average in the interior and upper Yukon River 2015 Addi>onal Ice Informa>on Teamwork: 6 mini-­‐trucks work together to pull a swamped vehicle out of the Kwethluk River Photo courtesy of Bethel Search and Rescue •  No truck travel on the Kuskokwim River recommended March 31, compared to April 15th in 2014. •  Mid winter breakup in November with a sec>on of frozen jumbled ice along the lower Kuskokwim River •  Reports from the Yukon River indicate closer to ‘normal’ ice condi>ons Snow Pack on April 1 2015 Spring Temperatures Tools for Forecas>ng Break-­‐up •  The past –  Long term trends and changes –  Composite averages (when some criteria met) •  Models of spring temperatures –  Break-­‐up >ming and severity are strongly (not totally) controlled by temperatures during the spring Timing of Break-­‐up has Changed Years of Early Break-­‐up April Temperature Departures Years of Late Break-­‐up April Temperature Departures Years with Significant Ice Jam Flooding on the Yukon River (1979-­‐2014) Climate Indices Break-­‐up Timing or Severity •  Indices without iden>fied skill –  Pacific Decadal Oscilla>on Index –  ENSO (El Niño or La Niña) •  Indices with some iden>fied skill –  Late Winter Western Pacific SSTs Correla>on of Temperature and western Pacific Sea Surface Temperatures Warm Western Pacific Climate Model Forecast •  Same idea as weather models: start from present condi>ons and go forward –  Basic equa>ons governing ocean-­‐atmosphere-­‐
land interac>ons plus “fudge factors” •  Unlike most weather models –  Fully couple ocean-­‐atmosphere –  Lower horizontal and ver>cal resolu>on End of April and Early May Climate Forecast System Weeks 3 and 4 Temperature anomalies (1999-­‐2010 model climatology) Dynamic Climate Forecasts for May •  Seven different climate forecast systems •  3-­‐categories •  >50% forecasts are significantly above normal for May What does that mean? •  Based on the current and forecast condi>ons we expect break to trend towards a thermal breakup on most major rivers with two caveats. •  Thermal to dynamic breakup expected for the Upper Yukon and a dynamic Breakup for the Arc>c. •  The spring breakup flood poten>al is currently rated as low to low-­‐moderate statewide. •  Although flood poten>als is rated as low, flooding can s>ll occur if ice jams form upstream or downstream from a community. Caveat for a Thermal Breakup •  Normally spring breakup is dynamic and moves from the headwaters of a river downstream in a linear fashion. •  A thermal breakup occurs when there is not enough snowmelt to push ice downstream and even though ice strength deteriorates significantly, breakup may actually occur later than normal. •  During a thermal breakup no coherent breakup front develops in this scenario and mul>ple loca>ons begin to see ice movement simultaneously. •  Ice Jam flooding from a thermal breakup is rarely serious, but is s>ll possible. •  Timing of breakup during a thermal breakup may range from several days earlier to several days later than normal and is oten inconsistent up and down a reach of river. Flood Outlook Poten>al h/p://aprfc.arh.noaa.gov Breakup Map h/p://aprfc.arh.noaa.gov Sag River Aufeis Flooding Image courtesy of Sanmei Li, George Mason University h/p://dot.alaska.gov/nreg/dalton-­‐updates/ Image courtesy of Alaska Department of Transporta>on and Public Facili>es Tanana at Nenana Yesterday Image courtesy of Borealis Broadband The End! Ques>ons? Supplemental Slides Ice Jam Loca>ons in Alaska 1 Ice Jam 2 -­‐ 5 Ice Jams 5 -­‐ 10 Ice Jams > 10 Ice Jams Sewage lagoon breached 8:00PM May 27th 2:00PM May 28th •  2nd highest flood crest on record ater 1971 – 11 feet above flood stage 7:00PM May 28th 8:00PM May 28th