Marine Ice Atlas for Cook Inlet, Alaska N D. M ATHAN ULHERIN W B. T III ALTER UCKER O P. S RSON MITH W J. L ILLIAM EE COVER: On a clear day in February, Mt. Iliamna is seen beyond close pack ice in Lower Cook Inlet. The ice cover is young, grey-white ice, first-year thin pancakes, and small floes of 7 to 8 tenths concentration. (Photo by Orson Smith) May 2001 This atlas and other products of the Cold Regions Research and Engineering Labo- ratory are available through CRREL’s web site: http://www.crrel.usace.army.mil US Army Corps National Oceanic of Engineers and Atmospheric ® Administration Engineer Research and Development Center National Ocean Service Marine Ice Atlas for Cook Inlet, Alaska N D. M ATHAN ULHERIN W B. T III ALTER UCKER O P. S RSON MITH W J. L ILLIAM EE Prepared by Sponsored by U.S. Army Corps of Engineers U.S. Department of Commerce Engineer Research and Development Center National Oceanic and Atmospheric Cold Regions Research and Engineering Administration Laboratory National Ocean Service ERDC/CRREL TR-01-10 Office of Response and Restoration PREFACE This report was prepared by Nathan D. Mulherin, Research Physical Scientist, and Walter B. Tucker III, Geophysicist, Snow and Ice Division, U.S. Army Engineer Research and Development Center, Cold Regions Research and Engineering Laboratory (CRREL), Hanover, New Hampshire; and Dr. Orson P. Smith, Associate Professor, and William J. Lee, Research Analyst, School of Engineering, University of Alaska Anchorage (UAA). The publication was a product of the Cook Inlet and Prince William Sound Navigation Safety and Efficiency Project and was funded by the National Oceanic and Atmospheric Adminis- tration, National Ocean Service, Office of Response and Restoration. The authors are grateful to Dr. Andrey Proshutinsky, Arctic Chair in Marine Science at the Naval Postgraduate School, and to Craig Evanego, Ice Analyst at the National Naval Ice Center, for their technical reviews of the manuscript. Grateful acknowledgment is also ex- tended to the World Meteorological Organization, Geneva, Switzerland, for permission to use their sea ice nomenclature (WMO 1970), which appears here as Appendix A; to Russell Page, Meteorologist and Ice Analyst, National Weather Service Forecast Office in Anchor- age, Alaska, for helpful discussions concerning Cook Inlet ice analysis and forecasting; and to Dwight Pollard, State Climatologist, Alaska State Climate Center, Anchorage, Alaska, for assisting in the retrieval of archived NWS ice maps. They also thank MSgt John Johnson, Analyst, and Capt. Gary Marsteller, Assistant Chief of the Climatological Applications Team 2, Air Force Combat Climatology Center, Asheville, North Carolina, for compiling and summarizing the climatological data. Many other individuals at CRREL and UAA were instrumental in producing this report. Those at CRREL include Paul Cedfeldt, Physical Scientist, Geochemical Sciences Divi- sion, for providing advice and assistance in formulating our geographic information data- base; Brian Tracy, Physical Scientist, Remote Sensing/GIS Center, for accessing satellite images; Jane Mason and Dawn Boden for figure preparation; David Cate for editing; and John Severance for final production. Melanie Hartman and Cathy Huot at UAA assisted in compiling the GIS database from the NWS ice charts. The contents of this report are not to be used for advertising or promotional purposes. Citation of brand names does not constitute an official endorsement or approval of the use of such commercial products. ii CONTENTS Preface....................................................................................................... i Abbreviations and conversions.................................................................. vi 1 Introduction ............................................................................................. 1 2 Cook Inlet Physical Description............................................................... 3 2.1 Regional geography.................................................................. 3 2.2 Cook Inlet’s Head region........................................................... 3 2.3 Upper Cook Inlet ....................................................................... 6 2.4 Lower Cook Inlet ....................................................................... 6 3 Cook Inlet Marine Ice.............................................................................. 9 3.1 Ice types.................................................................................... 9 3.2 General marine ice environment............................................... 13 3.3 Theoretical ice growth and melt ................................................ 17 3.4 Cook Inlet marine ice data......................................................... 18 4 Expected Ice Conditions ......................................................................... 25 Map Set 1. Mean ice concentration and stage of development ...... 26 Map Set 2. Probability of occurrence for ice of any stage of development and ice of any concentration.................................. 35 Map Set 3. Probability of occurrence for ice of any stage of development and ice of at least 5/10ths concentration................ 44 5 Oceanography......................................................................................... 53 5.1 Bathymetry................................................................................ 53 5.2 Currents and tides..................................................................... 53 6 Climatology ............................................................................................. 59 6.1 Source and description of climatological data for Cook Inlet..... 59 6.2 Station climatologies ................................................................. 61 6.3 Duration of daylight ................................................................... 71 iii 7 Literature Cited........................................................................................ 75 Appendix A: Sea Ice Nomenclature, Arranged by Subject......................... 79 Appendix B: Example of a Cook Inlet Ice Cover Analysis Issued by the National Ice Center in Suitland, Maryland............................ 87 Appendix C: Procedure Used to Create the Composite Cook Inlet Ice Charts............................................................................. 91 Appendix D: Air Temperature ..................................................................... 95 Appendix E: Wind....................................................................................... 109 Appendix F: Wind Chill............................................................................... 123 Appendix G: Sea Level Pressure............................................................... 125 Appendix H: Bibliography........................................................................... 139 ILLUSTRATIONS Figure 1. Cook Inlet and relief map of surrounding region......................... 4 Figure 2. Place names of the Head Region of Cook Inlet.......................... 5 Figure 3. Young, gray, and gray-white ice, some floes white with snow cover, moving with the tide past the Port of Anchorage in Lower Knik Arm .................................................................... 5 Figure 4. Place names of Upper Cook Inlet............................................... 6 Figure 5. Place names of Lower Cook Inlet............................................... 7 Figure 6. Brash ice clogging Homer’s small boat harbor to an unusual extent...................................................................... 8 Figure 7. Relationship between the temperature of maximum density and the freezing point of water with respect to salinity................ 10 Figure 8. Relationship between the thickness of young sea ice, accumu- lated freezing degree-days, and snow cover thickness........ 10 Figure 9. Typical mixed-ice conditions in Upper Cook Inlet, featuring ice floes, both level ice and shove-thickened pans, interspersed with broken and brash ice in various first-year thin stages of development.................................... 14 Figure 10. Dates of significant ice formation at the Phillips Platform with respect to freezing degree-days........................................... 16 Figure 11. Mean monthly freezing and thawing degree-days for 1974– 1997 assuming base temperatures of 0 and –1.8°C, respectively, for four locations on Cook Inlet........................ 20 Figure 12. Seasonal variation of freezing and thawing degree-days for 1974–1997 for four locations on Cook Inlet.......................... 21 Figure 13. Season total FDDs for Anchorage, Alaska................................ 21 Figure 14. Radarsat-1 SAR imagery showing the Forelands area of Cook Inlet at near low tide on December 30, 1998 .............. 23 Figure 15. Example of a sea ice analysis chart issued by the Alaska Region Headquarters of the National Weather Service........ 24 Figure 16. Cook Inlet bathymetry............................................................... 54 iv Figure 17. Tidal mudflats in Upper Cook Inlet and the Head Region......... 54 Figure 18. General surface circulation pattern in Cook Inlet...................... 55 Figure 19. Summer surface circulation pattern in Lower Cook Inlet .......... 56 Figure 20. Tidal ranges at various locations around Cook Inlet................. 57 Figure 21. Alaska’s climatic zones ............................................................. 60 Figure 22. Weather summary for Anchorage International Airport............. 62 Figure 23. Average percent possible sunshine at Anchorage International Airport from 1955 to 1993..................................................... 63 Figure 24. Weather summary for Kenai Municipal Airport.......................... 65 Figure 25. Weather summary for Homer Municipal Airport........................ 67 Figure 26. Weather summary for Kodiak Municipal Airport........................ 69 Figure 27. Median monthly precipitation from 1961 to 1990 for four Cook Inlet locations.............................................................. 70 Figure 28. Total length of daylight for Alaska locations .............................. 71 TABLES Table 1. Vessel and structure damage in Cook Inlet caused by floating ice ............................................................................ 11 Table 2. Dates of river ice break-up and freeze-up.................................... 13 Table 3. Dates of first significant ice and ice-out for northern Cook Inlet... 15 Table 4. Dates of first significant ice for Upper and Lower Cook Inlet, and corresponding freezing degree-days at Anchorage and Kenai, respectively ........................................................ 16 Table 5. Ice design criteria for Cook Inlet petroleum industry platforms..... 17 Table 6. Accumulated freezing and thawing degree-days at Anchorage, Alaska, and calculated sea ice growth and melt in Cook Inlet ............................................................................. 19 Table 7. Stream flow data for the Matanuska, Knik, and Susitna Rivers.... 55 Table 8. Location and description of first-order Cook Inlet meteorological stations used in this study .................................................... 60 Table 9. Local times of sunrise and sunset at Kenai, Alaska, for the year 2000.............................................................................. 72 v ABBREVIATIONS ACRC Alaska Climate Research Center AEIDC Alaska Environmental Information and Data Center AFCCC Air Force Combat Climatology Center API American Petroleum Institute asl above sea level AVHRR Advanced very high resolution radiometer DMSP OLS Defense Meteorological Satellite Program Operational Linescan System FDD freezing degree-day GIS Geographic information system MLLW mean low low water NCDC National Climatic Data Center NCEP National Centers for Environmental Prediction NIC National Ice Center NOS National Ocean Service NWS National Weather Service POR period of record ppt parts per thousand SAR Synthetic aperture radar SSM/I Special sensor microwave/imager TDD thawing degree-day USACE U.S. Army Corps of Engineers USCB U.S. Census Bureau USCG U.S. Coast Guard USNO U.S. Naval Observatory WMO World Meteorological Organization CONVERSIONS Distance 3.28084 ft = 1 m 0.53996 nautical miles = 1 km 0.62137 U.S. statute miles = 1 km Velocity 0.86898 knots = 1 mph 1.94385 knots = 1 m/s 0.62137 U.S. statute miles/hr = 1 km/hr 0.44704 m/s = 1 U.S. statute miles/hr 1.1508 U.S. statute miles = 1 nautical mile 0.53995 knots = 1 km/hr Flow volume 0.02832 m3/s = 1 cfs vi 1 INTRODUCTION C ook Inlet is a 350-km-long estuary located in the sea ice extent and character for Cook Inlet in par- south-central Alaska. Approximately half the ticular. The maps were based on a large array of pub- population of Alaska resides near its shores. lished and unpublished sources and the several inter- Anchorage, situated near its northern end, is the state’s mittent ice maps that had been issued by the largest city and a major center for commerce, indus- National Weather Service (NWS). Shortly thereafter try, recreation, and transportation. Shipping routes in the NWS began to regularly issue Cook Inlet ice Cook Inlet serve year-round oil and natural gas prod- charts showing the current conditions as an aid uction in central Cook Inlet and the import of con- to navigation and fishing activities. As of April 1999, sumer goods and petroleum products to the Port of approximately 675 such charts had been archived and Anchorage. The Port serves 80% of Alaska’s pop- are now available for analysis. One purpose of this ulation and its four largest military bases. publication is to present an updated time series The marine ice environment of Cook Inlet is unique. of the mean and extreme sea ice conditions that we Tidal height variations at Anchorage are the second derived from these charts. In addition, this report is a most extreme in the world. At 9 m, they are exceeded compilation of previously published and unpublished only by those that occur in eastern Canada’s Bay of information on the severity of winter conditions that Fundy. The extreme tidal range and the generally shal- prevail in a region important for the nation’s commer- low nature of Cook Inlet produce extreme tidal cur- cial activities. The information contained here is in- rents as well. Tidal currents at maximum flow are typi- tended to aid engineers, ship owners, port and gov- cally 4 knots and have been reported to be as high as 8 ernment officials, planning agencies, and mariners in knots. These bathymetric and oceanographic factors, ship design and modification criteria; in planning in combination with the winter climate, result in the safe and efficient navigation in Cook Inlet; and in re- production of large quantities of marine ice in Cook gional development decision-making and contingency Inlet that can impact human activities for substantial planning. periods each year. Section 2 of this atlas provides a physical descrip- A report by Gatto, published in 1976, was the most tion of Cook Inlet and the surrounding region. Sec- comprehensive information publicly available up to tion 3 describes the Inlet’s marine ice environment. that time on the oceanography of Cook Inlet. A sec- Section 4 contains the maps of Cook Inlet ice cover tion of that report was devoted to the Inlet’s sea ice that we created from a quantitative analysis of the environment. However, it wasn’t until 1983, when the NWS ice charts. Sections 5 and 6 describe the oceano- Alaska Marine Ice Atlas (LaBelle et al.) appeared, that graphic and climatic factors, respectively, that con- a time series of maps became available that depicted tribute to the ice regime of Cook Inlet. 2 COOK INLET PHYSICAL DESCRIPTION 2.1 Regional geography Alaska Range blends almost imperceptibly with the Cook Inlet is oriented southwest-northeast and cen- Aleutian Range, which continues along the Lower tered at approximately 60°N latitude and 152°W lon- Inlet’s western edge, with summits averaging 1,525 gitude (Fig. 1). The land surrounding Cook Inlet con- m (5,000 ft) in elevation. However, many of the Aleu- sists of vast tidal marshlands, rising up to piedmont tian Mountains are much taller and are active volca- lowlands with many lakes and ponds, to rugged gla- noes. Of these, and within sight of Cook Inlet, are cially carved mountains. Estuarine tidal marshes are Mounts Spurr (3,374 m [11,070 ft]), Redoubt (3,108 prevalent at the mouths of the rivers and as large por- m [10,197 ft]), Iliamna (3,053 m [10,016 ft]), and tions of the bays about the Inlet. The Kenai Peninsula Douglas (2,153 m [7,064 ft]). Mount Augustine is a encloses Cook Inlet to the southeast. Here, the Kenai 4,025-m [13,205-ft] volcano that rises abruptly out of Lowlands, immediately adjacent to the Inlet, is an area the waters of the Lower Inlet as Augustine Island. of flat marshland, lakes, and bogs that gradually rises Extending north from Cook Inlet and enclosed by up to rolling piedmont foothills. These lowlands and the Talkeetna and Alaska Ranges are the Susitna Low- foothills extend over a distance of 50–65 km eastward lands. They are a poorly drained, glaciated basin, ap- to the Kenai Mountains, which rise to approximately proximately 145 km long and 130 km wide, that is 1,500 m (5,000 ft) above sea level (asl). characterized by its extensive ground moraine, Immediately east of the state’s largest city, Anchor- outwash plains, drumlin fields, eskers, kettles, and age, are the Chugach Mountains, which rise abruptly swampland. to around 2,150 m (7,000 ft) asl. The climate of the Chugach Range is strongly influenced by its close 2.2 Cook Inlet’s Head region proximity to the Gulf of Alaska. The cold, polar air Cook Inlet can be described as three distinct re- masses that sweep down across Alaska’s interior and gions (the Head, the Upper Inlet, and the Lower Inlet) collide with the Gulf’s warmer, moisture-laden air pro- (Nelson 1995). The Head, or northernmost end of the duce over 15 m of snowfall annually. Inlet, is composed of two long and narrow bays known The Talkeetna Range, northeast of the Inlet, is sepa- as Knik and Turnagain Arms (Fig. 2). Knik Arm ex- rated from the Chugach Mountains to the south by the tends inland approximately 50 km to the confluence Matanuska River valley and from the Alaska Range of the Knik and Matanuska Rivers from a line con- to the north by the Susitna River. The Talkeetnas reach necting Points Woronzof and MacKenzie. It ranges 2,150 m (7,000 ft) in elevation. The Alaska Range con- from 2 to 10 km wide over its length. The upper two tains several of the highest peaks in North America, thirds is almost entirely exposed mudflats during low including Denali (or Mt. McKinley – 6,194 m [20,320 tide. The Port of Anchorage is located at the mouth of ft]) and Mt. Foraker (5,304 m [17,400 ft]). However, Ship Creek on the southeast shore of Knik Arm, ap- aside from the several giants (fewer than 20 peaks in proximately 7 km northeast of Point Woronzof and the range are taller than 3,000 m), these mountains 280 km from the Gulf of Alaska. Anchorage (with a are generally 2,150–2,750 m (7,000–9,000 ft) high. population estimated at 255,000 in 1998) is nearly Curving around to the northwest of the Inlet, the eight times larger than the state’s second largest city 3