Technical Reports

Sea Ice – Abstracts

• Propagation of Uncertainties in Sea Ice Thickness Calculations from Basin-Scale Operational Observations: A Report Prepared for the International Ice Charting Working Group and the National/Naval Ice Center
  
  Cathleen A. Geiger
  ERDC/CRREL Technical Report 06-16
  Abstract
  Sea ice serves as a natural flux monitor of the global heat balance. This capability is attributed to the unique location of sea ice at the interface of the world’s two largest circulation systems—the air and ocean. The increased awareness of warming in the polar region has precipitated increased efforts to measure sea ice thickness as an index for global heat changes. This increased awareness has brought with it the development of several new prototype in situ, telemetry, and satellite remote sensing instruments. Each of these provides a means for measuring part or all of the frozen material at the air–sea interface, but each comes with considerable limitations. The integration of these measurements into basin-scale objective analysis fields will serve as important input for global climate models, much like current-day weather forecasting systems and the El-Niño monitoring system. As the various thickness monitoring tools begin to develop, it is critical that standards be established to record the quality of these data. This report addresses the data quality issues by examining a robust method for tracking uncertainties in measurements. The data sets considered are the two existing operational basin-scale systems: ship-based observations and satellite composite analysis. Illustrative examples are included.

• Improving Oil Spill Response in Ice-Covered Waters
  
  Leonard J. Zabilansky, David F. Dickins, Ian Buist, Kathleen D. White, and Gioia Cattabriga
  ERDC/CRREL Technical Note 06-2
  Abstract
  Exploration, development, and production of oil from ice-covered seas is accelerating because crude oil supplies in easy-to-access areas of the world are dwindling. Although offshore drilling and production systems are designed and regulated to be very safe, oil spills in ice-covered waters do occur, presenting challenges unlike those that occur in open water. This technical note describes how CRREL’s Ice Engineering Facility supported two research programs intended to improve spill response in ice-covered waters: developing new technologies to detect oil trapped under or within solid ice, and testing herding agents as a technique to thicken oil slicks for burning and/or mechanical recovery in situations where ice concentrations hinder the natural formation of thick oil slicks.

• Marine Ice Atlas for Cook Inlet, Alaska
  Nathan D. Mulherin, Walter B. Tucker III, Orson P. Smith, and William J. Lee
  ERDC/CRREL Technical Report 01-10

  Abstract
  Cook Inlet, a 350-km-long estuary located in south-central Alaska, is a region of great importance to the economy of the entire state. Approximately half the population of Alaska resides near its shores, and Anchorage, at its northern end, is the state's largest city and a focus for commerce, industry, recreation, and transportation. Tidal height variations at Anchorage are the second most extreme in the world, exceeded only by those in Canada's Bay of Fundy. Cook Inlet's extreme tidal range and the shallow bathymetry produce extreme tidal currents as well. During winter the marine ice that forms in the Inlet can have a substantial impact on human activities. This report is a compilation of previously published and unpublished information on the climatic, meteorological, oceanographic, and hyrodynamic conditions that influence the marine ice cover in Cook Inlet. Biweekly maps, based on historical conditions from 1984 through 1999, are presented that show the expected concentrations and stages of development of the ice cover. These maps were produced by re-analyzing approximately 675 archived ice charts that were produced by the National Weather Service between 1984 and 1999, using ArcView™ GIS software.

  Accounting for Clouds in Sea Ice Models(436 K)

  Aleksandr P. Makshtas, Edgar L Andreas, Pavel N. Svyashchennikov, and Valery F. Timachev
  CRREL Report 98-9

  Abstract
  Over sea ice in winter, the clouds, the surface-layer air temperature, and the longwave radiation are closely coupled. This report uses archived data from the Russian North Pole (NP) drifting stations and recent data from Ice Station Weddell (ISW) to investigate this coupling. Both Arctic and Antarctic distributions of total cloud amount are U-shaped: that is, observed cloud amounts are typically either 0–2 tenths or 8–10 tenths in the polar regions. These data obey beta distributions; roughly 70 station-years of observations from the NP stations yielded fitting parameters for each winter month. Although surface-layer air temperature and total cloud amount are correlated, it is not straightforward to predict one from the other, because temperature is normally distributed while cloud amount has a U-shaped distribution. Nevertheless, the report presents a statistical algorithm that can predict total cloud amount in winter from surface-layer temperature alone and, as required, produces a distribution of cloud amounts that is U-shaped. Because sea ice models usually need cloud data to estimate incoming longwave radiation, this algorithm may be useful for estimating cloud amounts and, thus, for computing the surface heat budget where no visual cloud observations are available but temperature is measured—from the Arctic buoy network or from automatic weather stations, for example. The incoming longwave radiation in sea ice models is generally highly parameterized. The report evaluates five common parameterizations using data from NP-25 and ISW. The formula for estimating incoming longwave radiation that König-Langlo and Augstein developed using both Arctic and Antarctic data has the best properties but does depend nonlinearly on total cloud amount. This nonlinearity is crucial since cloud distributions are U-shaped, while common sources of cloud data tabulate only mean monthly values. The report therefore closes by using a one-dimensional sea ice model to investigate how methods of averaging cloud amounts affect predicted sea ice thickness in the context of the five longwave radiation parameterizations.

  FREZCHEM2: A Chemical Thermodynamic Model for Electrolyte Solutions at Subzero Temperatures (149 K)

  Mikhail V. Mironenko, Steven A. Grant, Giles M. Marion, and Ronald E. Farren
  CRREL Report 97-5

  Abstract
  This report documents a Fortran version of a chemical thermodynamic model for aqueous electrolyte solutions at subzero temperatures, FREZCHEM2, which is a further development of the FREZCHEM model. The model uses thermodynamic data of Spencer-Møller-Weare that permit the calculation of chemical equilibria in the Na-K-Ca-Mg-Cl-SO₄-H₂O system between –60 and 25°C at atmospheric pressure. It applies the Gibbs energy minimization method for chemical equilibrium computation combined with Pitzer equations for activity coefficients and water activity calculation. The model includes both the freezing (melting) reaction pathway at fixed water amount and the evaporation (dilution) pathway at fixed temperature. The FREZCHEM2 model can be extended with respect to independent components, electrolyte species, and solids, and if corresponding thermodynamic data are available, the model may be used to compute chemical equilibria in any systems that include aqueous-solution and/or one-component solid phases.

  The 1994 Arctic Ocean Section: The First Major Scientific Crossing of the Arctic Ocean (6.9 MB)

  Edited by Walter Tucker and David Cate
  Special Report 96-23

  Abstract
  None available.

  The Northern Sea Route: Its Development and Evolving State of Operations in the 1990s (3 MB)

  Nathan D. Mulherin
  CRREL Report 96-3

  Abstract
  The summer of 1991 marked the first time in recent history that Russia offered to escort ships of other countries across the Northern Sea Route (NSR). For moving cargo between the North Pacific region and Northern European ports, the NSR, along Russia´s northern coastline, is between 35 and 60% shorter than the traditionally used routes through the Suez and Panama Canals. In addition to its shorter distance, there already exists an extensive ports and shipping infrastructure, a current cargo base, and the potential for developing new markets in Russia and other northern areas. These incentives are attracting considerable attention from the international shipping community, including that portion servicing Alaskan and northwestern U.S. ports. This report is a general compilation of the historical usage, recent trade developments, the current regulatory climate, the physical environment, the ports and navigational infrastructure, cost factors, and practical considerations that may shape future U.S. interests in the route.

  Development and Results of a Northern Sea Route Transit Model (1.8 MB)

  Nathan D. Mulherin, Duane T. Eppler, Tatiana O. Proshutinsky, Andrey Yu. Proshutinsky, L. Dennis Farmer and Orson P. Smith
  CRREL Report 96-5

  Abstract
  For a Corps of Engineers reconnaissance study, we developed a numerical model to estimate the time needed for various ship types to transit the Russian Northern Sea Route. We simulated liquid bulk, dry bulk, and container ship transits during the months of April, June, August, and October. In the model, probability distributions for various ice, ocean and atmospheric inputs are exercised by a Monte Carlo algorithm to generate combinations of conditions that affect ship speed. The speed, dependent on the established environment during each time and distance segment, is read from empirically derived lookup tables. Daily ship rates and Russian passage fees were applied to calculate the relative total costs for moving the various cargoes over the route. The model´s development, limiting assumptions, simulation logic, data inputs, and resulting output are discussed.

  Electromagnetic Induction Sounding of Sea Ice Thickness (459 K)

  Austin Kovacs, Deborah Diemand and John J. Bayer, Jr.
  CRREL Report 96-6

  Abstract
  Field results from a man-portable electromagnetic induction sounding instrument, with special plug-in data processing modules for the remote measurement of sea ice thickness, are discussed. The field trials indicate that the instrument was capable of estimating undeformed sea ice thickness, with a snow cover, generally within about 5% of the drill hole measured thicknesses from about 1.25 to 4.5 m. No ice under 1.25 m was sounded in this study. Instrument thickness determinations of multiyear sea ice over about 4.5 m thick showed larger deviation from the drill hole snow and ice thickness measurement. It is proposed that the undulating multiyear sea ice relief is the major cause of the EM deviation.

  Sea Ice: Part I. Bulk Salinity Versus Ice Floe Thickness (697 K)
  

  Austin Kovacs
  CRREL Report 96-7

  Abstract
  Mathematical expressions have been established for estimating the bulk salinity of Arctic and Antarctic sea ice vs. ice floe thickness. The ice salinity vs. thickness relationships are based on data for over 400 sea ice cores compiled from numerous sources. The results show that the bulk salinity of first-year sea ice decreases in an exponential trend with ice sheet thickness. A similar trend reoccurs as the winter ice passes through the melt season. The expression for the bulk salinity S_B in ‰ for first-year sea ice from 10 to 200 cm thick is S_B = 4.606 + 91.603/T_F where T_F is the ice floe thickness in centimeters.

  Sea Ice: Part II. Estimating the Full-Scale Tensile, Flexural, and Compressive Strength of First-Year Ice (323 K)

  Austin Kovacs
  CRREL Report 96-11

  Abstract
  Sea-ice salinity, density, and temperature data were used to develop new methods for determining the bulk brine volume and porosity of sea-ice floes. Methods for estimating full-thickness ice sheet strength, based on large-scale field tests, are presented. The relationships among bulk sea-ice properties, strain rate, and strength are illustrated. A new constitutive equation was developed for predicting the full-thickness horizontal compressive strength s_c of first-year sea ice as a function of the applied strain rate and bulk porosity in the form , where parameters B₂ , n, and m are about 2.7 ¥ 10³ , 3, and –1, respectively, and and f_B are the ice strain rate and ice floe bulk porosity of sea ice, respectively. An estimate of the horizontal force that may develop between first-year sea-ice and a 90-m-wide structure is given. Estimating sea-ice strength based on remote ice conductivity measurements is also discussed conceptually.

  The Optical Properties of Sea Ice (570 K)

  Donald K. Perovich
  Monograph 96-1

  Abstract
  Sea ice is a translucent material with an intricate structure and complex optical properties. Understanding the reflection, absorption, and transmission of shortwave radiation by sea ice is important to a diverse array of scientific problems, including those in ice thermodynamics and polar climatology. Radiative transfer in sea ice is a combination of absorption and scattering. Differences in the magnitude of sea ice optical properties are due primarily to differences in scattering. Spectral variations are mainly a result of absorption. Changes in such optical properties as the albedo, reflectance, transmittance, and extinction coefficient are directly related to changes in the state and structure of the ice. Physical changes that enhance scattering, such as the formation of air bubbles due to brine drainage, result in larger albedos and extinction coefficients. The albedo is quite sensitive to the surface state. If the ice has a snow cover, albedos are large. In contrast, the presence of liquid water on a bare ice surface causes a decrease in albedo, which is more pronounced at longer wavelengths. Sea-ice optical properties depend on the volume of brine and air and on how the brine and air are distributed.

  Northern Sea Route Reconnaissance Study: A Summary of Icebreaking Technology (495 K)
  

  Devinder S. Sodhi
  Special Report 95-17

  Abstract
  Since the advent of steam power, icebreakers have been built to navigate in ice-covered waters. The hull forms of early icebreakers were merely an adaptation of open water hull shapes, by sloping bow angles more to create vertical forces for breaking ice in bending. However, these bow forms were found to be unsuitable for sea-going vessels because they push broken ice ahead of them. This experience led to construction of all sea-going vessels with wedge-shaped bows from 1901 to 1979. With the introduction of low-friction coatings and the water-deluge system, it is now possible to operate ships with blunt bows efficiently in broken ice. New developments in marine propulsion technology have also been incorporated to obtain better icebreaking efficiency and performance. Both fixed-pitch and controllable-pitch propellers are in use. Nozzles surrounding the propellers are also used to increase the thrust and to reduce ice–propeller interaction. Electrical and mechanical transmission systems have been used in icebreakers to improve the characteristics of the propulsion system. Though many types of prime movers are used in icebreakers, medium-speed diesel engines are the most popular because of their overall economy and reliability. Appendix A is a description of the Russian icebreaker Yamal, which is one of the largest and most powerful icebreakers of the world today. Appendix B contains an inventory of existing ships that are capable of navigating in at least 0.3-m-thick ice. Some of the present icebreakers are capable of navigating almost anywhere in the ice-covered waters of the Arctic and the Antarctic, and multi-purpose icebreakers have been built to operate not only in ice during the winter but also in open water doing other tasks during the summer. With sufficient displacement, power, navigation equipment, and auxiliary systems, future icebreakers that can operate in-dependently year-round in the Arctic and the Antarctic are well within the known technology and operational experience.