Alaska Climate Dispatch A state-wide seasonal summary & outlook Brought to you by the Alaska Center for Climate Assessment and Policy in partnership with the Alaska Climate Research Center, SEARCH Sea Ice Outlook, National Centers for Environmental Prediction, and the National Weather Service. Autumn 2011 Issue IN THIS ISSUE: Seasonal Climate Outlook and ENSO...page 1-3 Summer Wildfire Review...3-5 Summer Weather Review...5-7 Sea Ice Update...8-10 Photo Contest Winner...10 reasonably consistent with expectations across the state, as moderate or strong La Niña winters typically aren t significantly warmer than normal, and at many locations are often significantly colder than normal. Higher than average winter precipitation doesn t often occur over Southeast and southern coastal communities, but data varies in northern Alaska. Overall, there is a stronger correlation with ENSO Winter Seasonal Climate Outlook and ENSO Prepared by Corey Bogel and Rick Thoman, National Weather Service, Fairbanks Review of ENSO In the Fall 2010 edition of the Alaska Climate Dispatch we discussed the El Niño/Southern Oscillation (ENSO) and its expected impact on Alaska during the winter of 2010-11 (December through February). The Spring 2011 edition of the Dispatch contained a summary of temperatures and precipitation from the first order meteorological stations (operated by the National Weather Service meteorologists) in Alaska. The winter was characterized by noticeably colder than normal (30-year averages) temperatures in much of the Interior, with above normal temperatures along much of the west coast and Arctic coast. In general, precipitation was lower than normal, with above normal precipitation in parts of Northern and Western Alaska. This was Figure 1. Forecasts of sea surface temperature (SST) anomalies for the Niño 3.4 region (the tropical eastern Pacific Ocean). About half the dynamical and statistic models indicate that ENSO-neutral conditions will continue through the winter. The other half indicate that La Niña will re-develop in late fall or early winter. Figure courtesy of the International Research Institute for Climate and Society (portal.iri.columbia.edu). ACCAP is funded by the National Oceanic and Atmospheric Administration (NOAA) and is one of a group of Regional Integrated Sciences and Assessments (RISA) programs nation-wide. The RISA program supports research that addresses sensitive and complex climate issues of concern to decision-makers and policy planners at a regional level.
Winter Seasonal Climate Outlook and ENSO 2 to temperature than precipitation. Current state of ENSO NOAA s Climate Prediction Center (CPC) forecasted a moderate La Niña to occur during the winter of 2010-11, and a moderate to borderlinestrong La Niña was observed. During the spring of 2011 the La Niña weakened significantly, with ENSOneutral (neither La Niña nor El Niño) conditions observed by late spring through this summer. The ENSOneutral conditions are expected to persist through early fall. Beyond early fall, the forecasts are less certain with about half the dynamical and statistic models indicating that ENSO-neutral conditions will continue through the winter and the other half indicating that La Niña will re-develop late this Figure 2. Forecasts of sea surface temperature (SST) anomalies for the Niño 3.4 (tropical eastern Pacific) region from version 2 of the National Centers for Environmental Prediction (NCEP) Climate Forecast System. NCEP runs its own Climate Forecast System models, with the majority of the ensemble members indicating that La Niña will re-develop during the fall. Figure updated 3 August 2011. Figure 3. December 2011-Febraury 2012 temperature and precipitation outlooks produced by the Climate Prediction Center 18 Aug 2011. The forecast indicates enhanced chances that the 3-month average temperatures will be significantly colder than normal across much of interior Alaska as well as from the Aleutian Islands to the panhandle. There are also enhanced chances of significantly below normal precipitation across much of the eastern Interior. (www.cpc.ncep.noaa.gov/products/predictions/long_range/).
Winter Seasonal Climate Outlook and ENSO Fire Season Summary 3 fall or early winter (Figure 1, Page 1). Based on these model runs, the International Research Institute (IRI) for Climate and Society has estimated probabilities of 40%, 58% and 2% for La Niña, ENSO-neutral and El Niño conditions during the upcoming September-November period. For the November- January period, the probability of La Niña conditions increases slightly to 44%, while the probabilities of ENSO-neutral and El Niño conditions are 54% and 2%, respectively. The National Centers for Environmental Prediction (NCEP) runs its own Climate Forecast System models, with the majority of the ensemble members indicating that La Niña re-develops during the fall (Figure 2, page 2). So, what can we expect this winter? As we were heading into the fall of 2010, a moderate La Niña episode was already well underway, and confidence was high that the La Niña would continue well into the winter of 2010-11. This year, conditions are ENSO-neutral as we head into the fall of 2011. This is not a repeat of the conditions of 2010, which makes the forecast less certain. The CPC has issued a La Niña Watch, which means that ENSO-neutral or La Niña are equally likely by late this fall or winter. La Niña typically lasts 1-3 years, and it is not at all unusual for La Niña conditions to fade during the spring and summer only to reform again during the fall and winter. In recent winters this occurred in 2007-08 and 2008-09, and in three straight winters from 1998-1999 to 2000-2001. The latest outlook from the CPC for December 2011 through February 2012 appears to be putting a lot of weight toward the NCEP Climate Forecast System solution of a moderate La Niña re-developing late this fall into the winter. The official forecast from the CPC (Figure 3, page 2) indicates enhanced chances that the 3-month average temperatures will be significantly colder than normal across much of interior Alaska as well as from the Aleutian Islands to the panhandle. There are also enhanced chances of significantly below normal precipitation across much of the eastern Interior. ENSO is one of many climate signals that have a significant influence over Alaska (see Autumn 2010 issue). Even if the forecast does pan out, it is likely that periods of mild weather will occur, even if the average 3-month temperature is well below normal. 2011 Fire Season Review Prepared by Sharon Alden, Alaska Interagency Coordination Center; with contributions from Jennifer Northway, Alaska Fire Science Consortium; and Paul Duffy, Neptune, Inc. The 2011 Alaska fire season started with a roar after a very dry spring in the interior and quickly fizzled out with a rainy and cool summer. Only 292,095 acres have burned throughout the state in 2011. This figure is well below the long term average of about 1 million acres per year and the 10 year average of nearly 2 million (Figure 4, page 4). Last year s fire season (2010) ended with very high drought codes in the Upper Yukon Valley, indicating there was very little moisture in the deep organic layers of soil. This lead to the expectation of a busy spring in 2011 with carryover fires (fires that continue to burn in underground organic material throughout the winter). This indeed was the case Figure 5. Smoke jumpers landing on the Hastings Fire northwest of Fairbanks. Photo courtesy of Mike McMillan.
Fire Season Summary 4 Figure 4. Alaska fire history, by millions of acres, 1950-2010. Figure courtesy of the Alaska Interagency Coordination Center (http:// fire.ak.blm.gov/aicc.php). with several carryover fires, one being the 73,000 acre Pat Creek Fire located just outside of Stevens Village. By late May, the combination of the dry spring and human-caused ignitions and lightning caused two rapidly spreading fires to start just north of Fairbanks (Moose Mountain and Hastings) and another large fire in the hills northwest of Delta Junction (East Volkmar). These three early season fires sparked the attention of many local residents and required additional fire fighting support from Canada and the Lower 48. The fire danger in portions of the central Interior was at or near record levels by the end of May. However, a mid-june rainy period brought a shift in the overall weather pattern for the state. The typical summer weather pattern that brings high fire danger and lightning has an upper level ridge over Canada building into Alaska from the east. This summer, a large ridge formed over the Northern Pacific Ocean during mid-june and never moved over the state for any extended period of time. The bulk of Alaska s summer saw periodic precipitation (see Summer Weather Review, page 5). Some Interior locations did have below normal rainfall in July and August, however the frequency of even light rain was enough to prevent new fire starts, limit fire growth, and allow fire fighters to control and contain the fires that did start. In the Spring 2011 issue of the Dispatch, we published the Experimental Forecast of Area Burned for Interior Alaska (http://snap.uaf.edu/fire_prediction_tool/) prepared by Paul Duffy (Neptune, Inc.) in collaboration with the Bureau of Land Management and Alaska Fire Service. The median forecast went from high (over 1.5 million acres) in April to moderate (1 million acres) in both May and June, then shifted to low in July (less than 500,000 acres). This is juxtaposed against the actual area burned of roughly 300,000 acres burned. This July forecast reflected the relatively wet and somewhat cool summer across interior Alaska. The percentiles for the total monthly precipitation data used in the forecast model were: March = 7%, April = 39%, May = 13%, June = 87%, July = 77%, August = 80%. This reflects a dry spring followed by an exceptionally persistent and wet summer for June through August. The percentiles for the actual average monthly temperature data across the interior were: March = 39%, April
Fire Season Summary Summer Weather Summary 5 = 39%, May = 79%, June = 57%, July = 26%, August = 41%. Overall, the temperatures were roughly normal. The Pacific Decadal Oscillation has been in a moderately weak cool phase for most of the past several years, which generally corresponds to low to moderate fire activity; however, transitions from cool to warm phases have been associated with some (not all) of the largest fire years on record (e.g. 1957, 1969, 1977). Overall the forecast model of Area Burned for Interior Alaska could have performed better in the months of March and April; however, this tool has been designed to place a greater emphasis on correctly forecasting large fire years (versus the error of incorrectly overestimating the area burned in low fire years). The discrepancy between the March and April forecast versus the outcome for this year should provide data that will meaningfully improve subsequent forecasts. Summer Weather Conditions in Alaska Prepared by the Alaska Climate Research Center This article presents a summary of summer 2011 (June, July, August) temperatures and precipitation from the first order meteorological stations (operated by the National Weather Service meteorologists) in Alaska. It should be noted that the long-term normals for June and July are based on the 30 year time period 1971-2000, while the ones for August are based on 1981-2010. The National climate Data Center (NCDC) determined that the new normals (1981-2010) should be used starting August 1st. The new normals for Alaska and all other States can be obtained from: http://ggweather.com/normals/index.htm. The Winter 2011 issue of the Dispatch will include an article that will discuss the implications of the new normals. Temperature Figure 6 (below) shows the summer temperature departures from the respective 30-year averages for the first order stations in Alaska. Northwestern Alaska had temperatures noticeably warmer than the normal (i.e. positive deviation). Barrow and Kotzebue both displayed deviations of +1.5 F, continuing the seasonally above normal temperatures which were reported for the springtime. In contrast to this, southwestern Alaska was seasonally colder than normal. The highest negative deviations were observed for King Salmon (-2.8 F), Bethel (-2.4 F), Homer (-2.0 F), Nome and McGrath (both -1.4 F). An especially strong gradient (2.9 F) in the departures can be seen between Kotzebue and Nome. This is caused by a weakening of the Aleutian Low during the last decade, which has resulted in less advection, or movement, of the relatively warm air from the Northern Pacific into the Bering Sea. In southeastern Alaska the picture is complicated. Yakutat reported a deviation of +2.4 F, the highest positive deviation of all 20 first order stations in Alaska for the summer, while Juneau and Annette, further to the southwest, reported below normal temperatures Figure 6. Summer 2011 isotherm map of the deviation in temperature ( F) from the 30-year average based on all first order meteorological stations in Alaska (1971 2000, http://climate.gi.alaska.edu/). with values of -1.2 F for both stations. Interior Alaska was quite mixed, but generally close to normal. Going from north to south, Bettles was below normal (-0.9 F), above Fairbanks normal (+0.4 F), Big Delta on the cold side (-1.4 F), while Gulkana was warmer than would be expected (+0.3 F). In total, 14 of the 20 stations analyzed gave
Summer Weather Summary 6 Figure 7. 2011 summer precipitation departures (%) from the 30-year average (1971 2000, http://climate.gi.alaska.edu/). below normal temperatures for the summer season, while 6 measured above normal. The average deviation of all stations results in a small (-0.6 F) negative statewide deviation from the long-term average. More details can be seen in Table 1. Looking at the temperatures for the 3 summer months separately, June started out the season with temperatures generally above normal. Positive deviations greater than +2 F were observed for Kotzebue (+6.7 F), Yakutat (+3.1 F) and Gulkana (+2.1 F). Further, 15 of the 20 stations analyzed reported positive deviations. Substantially below normal temperatures (>2 F) were observed only in King Salmon (-2.2 F). The mean deviation of the 20 stations for the month was +0.6 F. In July, temperatures were below the 30-year average for most stations in Alaska, with an average value of the 20 stations at -1.3 F. Only 5 stations gave positive deviations, with Yakutat having the only substantial value of +3.5 F. Strong negative deviations in declining order were measured in Bethel (-4.6 F), Nome (-4.0 F), King Salmon (-3.7 F) and McGrath (-3.1 F). Like July, August was again colder than normal with 17 of the 20 stations reporting below normal values. The mean monthly deviation of all stations was -1.1 F. Only Barrow (+3.5 F) was substantially warmer than expected. The negative deviations were widespread and fairly uniform, with no station reporting a deviation larger than -3 F. Four new record high temperatures were set this summer: two in Cold Bay, and two in Valdez. In Cold Bay on August 11, the temperature reached 67 F/19.4 C, +2 F above the previous record from 2001. On August 16, a new record of 68 F/20 C was set, breaking the 1984 record of 65 F/18.3 C. On July 20, the high for Valdez was 74 F/23.3 C, just 1 above the record from 1980. August 12 saw the Valdez maximum temperature reach 75 F/23.8 C, breaking the record of 73 F/22.7 C from 1984. Conversely, there were 7 new record minimum temperatures set this summer. In addition to the two new high temperature records set at Cold Bay, there were two record lows set during the summer. The first was on August 4, with 39 F/3.9 C, notably colder than the previous record of 43 F/6.1 C from 1990. The next day the minimum temperature hit 37 F/2.8 C, -2 F under the record of 1963. King Salmon also set two record lows, 35 F/1.7 C on June 23, -1 under the record from 1949. Then on August 23, the temperature fell to 33 F/0.6 C, again -1 F under the record from 1969. As well as the previously noted two record high temperatures for Valdez this summer, there was also a new record low of 38 F/3.3 C on June 16, -3 F colder than the 1985 record of 41 F/5 C. McGrath entered the record count on July 17, with a low of 39 /3.9 C, -1 F below the 1997 minimum of 40 F. Kodiak set a new minimum with 39 F/3.9 C on August 6, breaking the 1942 record of 42 F/5.6 C. Precipitation The variability in precipitation is very high in Alaska. Ratios above 100 can be found in the annual values between the driest and wettest locations, therefore actual deviations from the long-term averages are not very meaningful. As a result, Figure 7 (above) presents these deviations as percentages above (+) or below (-) normal, where normal
http://accap.uaf.edu/dispatch.htm 7 Summer Weather Summary is the 30 year average. There can be also a strong gradient in precipitation from month to month in the long-term average, so the deviations for the seasonal values are calculated by adding the precipitation for the 3 months, then dividing by the long-term average for the 3 month period (Table 1). The average of the 3 monthly deviations may slightly depart from these values. In general the precipitation of summer 2011 was somewhat above normal (Figure 7); 70% of the stations reported above expected rainfalls. There were only 2 stations with negative deviations exceeding 10%, namely Yakutat (-27%) and Kodiak (-11%). Five stations had a very wet summer, here expressed with values of at least 40% above normal. In declining order of the deviations these are: Annette (+54%), Nome (+46%), Kotzebue and Bettles (+42%) and Juneau (+40%). Looking at the months separately, June was very slightly on the dry side, while July, and even more so August, were wetter then expected. For more details, see Table 1, which presents the temperature and precipitation deviations for the months and season. Given the wetter then normal summer, it will come as no surprise that there were quite a number of record precipitation events. There were a total of 27 new precipitation records for stations that have complete datasets. Nine of these records all occurred on August 20th when a strong storm hammered the Southeast. Port Alexander took the hardest hit and totaled 5.42in/13.8cm in one day, +2.27in/5.8cm above the record that had been in place since 1958. Ketchikan measured 4.63in/11.8cm, and Petersburg weighed in at 4.54in/11.5cm for the same day. In total, Juneau set four new record rainfalls this summer. Ketchikan, King Salmon, Klawock each set three new records, while Nome, Petersburg, St. Paul and Valdez set two records each. The combination of above normal temperatures and far below normal precipitation values in May in Interior Alaska lead to very dry surface condition at the beginning of the summer, giving the fire season an early start, and by the beginning of June, several large forest fires were burning in Interior Alaska (see Summer Fire Season Summary, page 3). Table 1. The deviation in temperature ( F) and precipitation (%) from the 30-year average (1971-2000 for June and July, 1981-2010 for August) is presented for all first order stations for each summer month and for the season (http:// climate.gi.alaska.edu/).
Sea Ice Update 8 Figure 8. Arctic sea ice concentrations (in percent) on September 1, 2011. Courtesy of Cryosphere Today, http://arctic.atmos.uiuc.edu/cryosphere/. Sea Ice Update Prepared by John Walsh, President s Professor of Climate Change & Chief Scientist, International Arctic Research Center, UAF. For the fifth consecutive summer, sea ice retreat in the Arctic has been extreme by historical (pre-2007) standards. At the end of August, the total Arctic ice coverage was evolving towards the lowest or second lowest ice coverage since 1978, when passive microwave satellite sensors began providing consistent coverage of Arctic sea ice. Figure 8 (above) shows the coverage of ice on September 1, 2011. Huge expanses of open water are present the Alaskan and Siberian sectors of the Arctic, with the pack ice boundary close to 80 latitude to the north of the Chukchi Sea. As recently as the 1970s and 1980s, there were years when sea ice remained sufficiently close to shore throughout the summer that barge resupply operations along Alaska s northern coast were threatened even in the late summer. Only in the eastern Beaufort Sea, west of Banks Island, are there presently some intrusions of sea ice, mainly remnants of older multiyear ice. According to the satellite passive microwave image in Figure 8, the Northwest Passage in Canada and the Northern Sea Route north of Russia are both free of ice, although the navigability of those routes still needs to be confirmed because the passive microwave sensors can fail to depict areas of scattered melting ice. For a perspective relative to the past decade, Figure 9 (page 9)shows the seasonal cycle of ice extent for each year from 2002 through 2011. Ice extent is defined as the area poleward of the sea ice edge, which has been traditionally been taken to be the 15% contour of ice concentration. In Figure 9, the 2011 ice extent is the red line, while the recordminimum year of 2007 is the black line. As of September 1, 2011 s ice retreat is second only to that of 2007, and is tracking very close to the 2007 record. The timing of the 2011 minimum may well determine whether a new record minimum extent is achieved in 2011. The June issue of the Dispatch summarized predictions of mean September ice extent for 2011, based on experimental forecasts submitted by ice researchers from around the world to the SEARCH (Study of Environmental Arctic Change) Sea Ice Outlook. The median forecast of the 2011 minimum extent was 4.7 million square kilometers, which is higher than the 2007 value (4.3 million square kilometers), but slightly less than the minimum of 4.9 million square kilometers
Sea Ice Update 9 Figure 9. Seasonal evolution of total Arctic sea ice extent for the years 2002-2011. The extent for 2011 (through the end of August) is shown in red; the record minimum year, 2007, is shown in black. Courtesy of IARC/JAXA Sea Ice Monitor, http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm reached in September 2010. All these values, including the median forecast of 4.7 million square kilometers, are well below the 1979-2007 mean September ice extent of 6.7 million square kilometers. Based on Figure 9, it appears that this median forecast will be close to, but likely slightly higher, than the actual 2011 value, which may be closer to the 2007 value of 4.3 million square kilometers. Any value in the 4.3-4.7 million square kilometer range will be approximately 40% below the 1979-2007 mean September ice extent. Finally, Figure 10 (right) shows the history of sea ice area for the entire period (1979-2011) of satellite passive microwave coverage. Ice area differs from extent (total area within the ice boundary) by excluding areas of open water poleward of the ice edge, i.e., it is the actual area covered by sea ice and is therefore smaller than the ice extent. The sea ice area on September 1 had decreased to 3.07 million square kilometers, essentially the same as the 2007 minimum of ice-covered area and about 60% below the mean minimum of the 1980s (Figure 10). The fact that the ice area loss is even more extreme than the ice extent loss indicates that there are now larger areas of open water within the ice edge, more Figure 10. Area covered by sea ice (excluding open water within the ice cover) from 1979 through 2011. The decreasing trend superimposed on the seasonal cycle is apparent, particularly in the past five years. Courtesy of Cryosphere Today, http://arctic.atmos.uiuc.edu/cryosphere/.
Sea Ice Update 10 so than even in 2007, pointing to a relatively fragile ice cover. The loss of older and thicker multiyear ice, as documented in the recent scientific literature, is consistent with this increase of open water within the outer ice boundary. The Arctic sea ice cover generally reaches its minimum in the second or third week of September, as shown in Figure 10 (page 9) for past years. The large amount of open water already present north of Alaska implies substantial absorption of solar energy during the summer. The absorbed energy will take some time to release back to the atmosphere, so a late freeze-up of the northern Alaskan coastal waters is likely. This late freeze-up will likely contribute to warmer-than-normal autumn temperatures in northern Alaska, as shown in the Climate Prediction Center s seasonal temperature outlook for northern Alaska (page 1-3). For more information about the Alaska Center for Climate Assessment & Policy, please contact us: accap@uaf.edu accap.uaf.edu (907) 474-7812 UAF is an affirmative action/equal opportunity employer and educational institution. Congratulations Dispatch Photo Contest Winner Mida Swan! In the Summer 2011 Dispatch, ACCAP announced a photo contest. This picture was taken by Mida Swan from the Native Village of Kivalina. Mida says I just wanted to share some of my pictures of things I ve never seen before. Our summers are fast becoming more unusual every year. Ice is melting and not really breaking up like it used to. With the warmer ocean temperatures the ice is melting from underneath and this information we got from our elderly Dad Joseph Swan Sr. who has been hunting on ocean ice his entire life. We have unstable shorefast ice lately. It tends to break up between November and January. These pictures were taken on June 19. The most amazing rainbow I ve ever seen. Incoming rain and the sun to my back around 11pm. Mida submitted several beautiful photos. Thanks to those who entered!