DATASTREME OCEAN WEEK TEN: 5-9 April 2004

• Tsunami Awareness Month in Hawaii -- Officials with the NOAA Pacific Tsunami Warning Center and the International Tsunami Information Center recently announced that the month of April is Tsunami Awareness in the Aloha State. Their announcement commemorating the destructive tsunami on 1 April 1946 that cost 159 people their lives. Several events and programs have been scheduled during this month to help educate and inform Hawaiians of the dangers associated with tsunamis, an ocean wave that is generated by a submarine earthquake, volcano or landslide and can travel great distances. [NOAA News]
• A major hurricane landfall is anticipated -- In preparing his updated 2004 hurricane forecast for the North Atlantic basin, Professor William Gray at Colorado State University stated that the odds appear to be very high that a major hurricane with sustained winds of 111 mph or higher will make landfall along the continental US during this upcoming hurricane season that commences on 1 June. [USA Today]
• An extraterrestrial marine weather report foreseen -- Scientists associated with the Cassini/Huygens mission are expecting that the lander could splashdown next January on an ocean that covers a portion of the surface of Titan. They speculate that the liquid surface, which could consist of liquid methane and ethane, could have wind-driven waves that could be seven times the height of typical waves on earth. [ESA News]
• California surfers face additional hazards-- Researchers at the University of California, Irvine recently reported on a study of surfers in California. They suggest that surfers near Los Angeles ran a greater health risks than in less urban coastal regions because of the higher coliform counts and pollutants in runoff of rainwater from the impermeable paved surfaces and roofs in urban areas. [Center for the Advancement of Health]
• Research on the Larsen Ice Shelf-- A geology professor at Hamilton College has been awarded a grant to study the history of the ice of Larsen Ice Shelf, the third largest ice shelf in Antarctica over the next three years. [Hamilton College]
• Alaska governor invites drilling in state waters near wildlife refuge -- Gov. Frank Murkowski announced that he plans to open lease sales in state waters offshore of the Arctic National Wildlife Refuge and the National Petroleum Reserve-Alaska. [ENN]
• A penalty assessed for illegal fishing -- A court in Perth, Australia convicted, fined and were ready to deport 32 crewmen on a Uruguayan fishing ship that were illegally fishing for the rare Patagonian toothfish in Australian waters. [ENN]
• The oceans seen as a major source of fuel -- Scientists at Imperial College in London recently reported on research into artificial photosynthesis that they hope would turn the oceans into a potentially boundless source of fuel. [Independent Newspapers]
• Cruise liner dumping restrictions negotiated -- The Washington State Department of Ecology has recently negotiated with cruise ship operators in an effort to reduce the amount of wastewater dumped from the large cruise liners in the state's inland marine waters. [US Water News Online]

• Global and US Hazards/Climate Extremes-- A review and analysis of the global impacts of various weather-related events, including drought, floods, and storms during the current month. [NCDC]
• Earthweek -- Diary of the Planet [earthweek.com] Requires Adobe Acrobat Reader.

Concept of the Week: Life on the Ice

Life exists on and within the floating sea ice cover of polar oceans. In the Arctic, for example, sea ice provides habitat for a variety of organisms, members of an ice-specific food web that include bacteria, viruses, unicellular algae, and small invertebrates. These organisms are adapted to tolerate dramatic changes in light intensity, temperature, and salinity.

As noted in Chapter 3, dissolved salts depress the freezing point of seawater. For example, at a salinity of 33 psu, the freezing point is about -1.9 °C. In autumn as temperatures fall, ice begins forming on the ocean surface as a porous structure of interlocking ice crystals filled with a salty liquid known as brine. The brine, representing about 10% to 30% of the ice volume, occupies tiny channels and pockets between and within the ice crystals. As winter progresses, the sea ice cover solidifies; pore space decreases; and the salinity of the brine increases. As long as the temperature remains above -5 °C, the ice is riveted by tiny passages having diameters ranging from a few micrometers to several centimeters. But when the temperature drops to lower values, the connectivity of the brine pores becomes minimal and the salinity of the brine can reach values approaching 250 psu. Ice organisms have the same temperature as the ice so that their survival within ice channels and pockets hinges on adaptations that prevent the growth of ice crystals in their bodies (e.g., some organisms accumulate fat-like materials in their bodies.)

Sea ice insulates the underlying seawater from the atmosphere so that a considerable temperature gradient develops between the ice surface (where mid-winter temperatures might plunge to -35 °C or lower) and the ice/seawater interface where the temperature is the same as the seawater (perhaps -2 °C). For this reason, most of the ice biomass is concentrated within the lowermost centimeters of the ice. Beginning in spring with the return of sunlight for photosynthesis, and continuing through summer, the populations of unicellular ice algae (often forming chains and filaments) living the lowermost portion of the sea ice explode. Several hundred species of unicellular algae living in the ice are the main primary producers in the Arctic. In fact, ice algae on average account for 4% to 26% of total marine primary productivity in seasonally ice-covered Arctic waters and up to 50% or more in perennially ice-covered waters. Dissolved organic matter from the wastes of ice algae is food for ice bacteria. Algae are eaten by crustaceans, rotifers (microscopic invertebrates), and turbellarians (flatworms). Tiny crustaceans (amphipods) live on the underside of the ice, feed on algae and seek shelter from predators in the brine channels. Juvenile stages of zooplankton also feed on the ice bottom community. With rising temperatures in spring, the solid ice cover breaks up into pack ice and individual floes that can transport organisms thousands of kilometers before melting and releasing their contents into the ocean.

Large warm-blooded animals also live on the sea ice. Birds (e.g., penguins in the Antarctic), seals, whales, and polar bears utilize sea ice for migration routes, hunting grounds, and rookeries. Seasonal changes in ice cover and thickness makes for a dynamic environment and requires animals to have excellent navigation skills.

Polar bears have a special adaptation that enables them to survive the extreme cold of the Arctic atmosphere. Scientists became aware of the effectiveness of this adaptation when they came up with a plan to census polar bears. Because white polar bears blend in with the snow-covered ice, scientists decided to locate and count the bears using thermal (infrared) imagery taken from an aircraft. They assumed that the polar bears would show up as hot spots on the images. However, scientists found that although they could often visually see the polar bears, the bears were not appearing on thermal imagery. Polar bear fur is so efficient as an insulating blanket that essentially no body heat was getting through the fur so that no heat signals reached the infrared sensor on the aircraft. Polar bear fur is made up of hollow tubes that function as very efficient insulators.

Concept of the Week: Questions

1. In the Arctic, most of the ice biomass occurs [(just below the surface)(at the base)] of the sea ice cover.
2. Populations of ice algae are largest in [(winter and fall)(spring and summer)].

• 6 April 1894...President Cleveland authorized to enforce Paris Award concerning the preservation of fur seals in Alaska. (USCG Historian's Office)
• 6 April 1909...The American explorer, Commander Robert E. Peary, USN, along with assistant Matthew Henson, and four Eskimos reported reaching the North Pole; however, navigational errors may have meant that they were a few miles away from the exact pole. (Naval Historical Center) (The History Channel)
• 6 April 1913...USRC Seneca, a derelict destroyer (whose mission was to locate and destroy abandoned wrecks that were still afloat and a menace to navigation), inaugurated the Revenue Cutter Service's participation in the International Ice Patrol. (USCG Historian's Office)
• 8-10 April 1958...A global 48-hour precipitation record was established at Aurere, La Reunion Island, when 97.1 inches of rain from a tropical cyclone fell on the Indian Ocean island. (The Weather Doctor)
• 8-14 April 1984...Intense Tropical Cyclone Kaimsy crossed and re-crossed the northern portion of Madagascar. Winds exceeding 112 mph destroyed 80 percent of Antseranana and Mahajanga. Rainfall from this system reached 27.99 inches. Eighty-two people were killed and 100,000 were made homeless. Damage was greater than 150 million US dollars. Rainfall totals reached 27.99 inches. (Accord's Weather Guide Calendar) (The Weather Doctor)
• 9 April 1770...Captain James Cook discovered Botany Bay on the Australian continent.
• 10 April 1877...The first of two great coastal storms struck the Virginia and North Carolina coasts. The Oregon Inlet was widened by three-quarters of a mile. The "entire topography of country is materially altered", according to a description of the altering of sand dunes at Cape Hatteras. (Intellicast)
• 10 April 1998...Northeast winds at 40 mph on the 9^th and 10^th combined with high levels of Lake Erie produced waves to 14 feet along the lakeshore in Ottawa and Sandusky Counties in Ohio. Much damage resulted, along with the destruction of 10 houses. Bulldozers needed to clear the debris from roads. Downtown Port Clinton streets were flooded. (Accord's Weather Guide Calendar)
• 11 April 1803...A twin-screw propeller steamboat was patented by John Stevens.

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Prepared by AMS DSOcean Central Staff and Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 2004, The American Meteorological Society.