Population status, seasonal variation in abundance, and long-term population trends of Steller sea lions (Eumetopias jubatus) at the South Farallon Islands, California

We examined seasonal and annual variation in numbers of Steller (northern) sea lions (Eumetopias jubatus) at the South Farallon Islands from counts conducted weekly from 1974 to 1996. Numbers of adult and subadult males peaked during the breeding season (May–July), whereas numbers of adult females and immature individuals peaked during the breeding season and from late fall through early winter (September–December). The seasonal pattern varied significantly among years for all sexes and age classes. From 1977 to 1996, numbers present during the breeding season decreased by 5.9% per year for adult females and increased by 1.9% per year for subadult males. No trend in numbers of adult males was detected. Numbers of immature individuals also declined by 4.5% per year during the breeding season but increased by 5.0% per year from late fall through early winter. Maximum number of pups counted declined significantly through time, although few pups were produced at the South Farallon Islands. The ratio of adult females to adult males averaged 5.2:1 and declined significantly with each year, whereas no trend in the ratio of pups to adult females was discernible. Further studies are needed to determine if reduced numbers of adult females in recent years have resulted from reduced survival of juvenile or adult females or from changes in the geographic distribution of females.

Origin of immature loggerhead sea turtles (Caretta caretta) at Hutchinson Island, Florida: evidence from mtDNA markers

Loggerhead sea turtles (Caretta caretta) are migratory, long-lived, and slow maturing. They are difficult to study because they are seen rarely and their habitats range over vast stretches of the ocean. Movements of immature turtles between pelagic and coastal developmental habitats are particularly difficult to investigate because of inadequate tagging technologies and the difficulty in capturing significant numbers of turtles at sea. However, genetic markers found in mitochondrial DNA (mtDNA) provide a basis for predicting the origin of juvenile turtles in developmental habitats. Mixed stock analysis was used to determine which nesting populations were contributing individuals to a foraging aggregation of immature loggerhead turtles (mean 63.3 cm straight carapace length [SCL]) captured in coastal waters off Hutchinson Island, Florida. The results indicated that at least three different western Atlantic loggerhead sea turtle subpopulations contribute to this group: south Florida (69%), Mexico (20%), and northeast Florida-North Carolina (10%). The conservation and management of these immature sea turtles is complicated by their multinational genetic demographics.

Pacific sea surface temperature associations with southwestern United States summer rainfall and atmospheric circulation

Pacific sea surface temperatures (SSTs) are examined for their associations with (1) summer rainfall, and (2) the latitude location of the mid-tropospheric subtropical high pressure ridge (STR) in the southwestern United States during 1945 to 1986. Extreme northward (southward) displacements of STR are associated with wet (dry) summers over Arizona and an enhanced (weakened) gradient of SST off the California and Baja coasts. These tend to follow winters marked by positive (negative) phases of the PNA, Pacific/North America, teleconnection pattern. Recent decadal variations of Arizona summer rainfall (1950s wet; 1970s dry) appear similarly related to southwestern United States synoptic circulation and eastern Pacific SSTs.

The Younger Dryas and millenial-scale oceanographic variability in the Sulu Sea, tropical western Pacific

EXTRACT (SEE PDF FOR FULL ABSTRACT): A high resolution, AMS carbon-14-dated sediment record from the Sulu Sea clearly indicates the Younger Dryas climatic event affected the western equatorial Pacific. Presence of the Younger Dryas in the tropical western Pacific indicates this climatic event is not restricted to the North Atlantic nor to high latitudes, but is global in extent.

Tree-ring records as indicators of air-sea interaction in the northeast Pacific sector

Climate conditions in land areas of the Pacific Northwest are strongly influenced by atmosphere/ocean variability, including fluctuations in the Aleutian Low, Pacific-North American (PNA) atmospheric circulation modes, and the El Niño-Southern Oscillation (ENSO). It thus seems likely that climatically sensitive tree-ring data from these coastal land areas would likewise reflect such climatic parameters. In this paper, tree-ring width and maximum lakewood density chronologies from northwestern Washington State and near Vancouver Island, British Columbia, are compared to surface air temperature and precipitation from nearby coastal and near-coastal land stations and to monthly sea surface temperature (SST) and sea level pressure (SLP) data from the northeast Pacific sector. Results show much promise for eventual reconstruction of these parameters, potentially extending available instrumental records for the northeastern Pacific by several hundred years or more.

Sea surface temperature and paleo-El Niño events in Santa Barbara Basin, AD 1841-1941

Like pages of a "natural coastal diary", successive layers of anoxic varved sediment in the central Santa Barbara Basin have been used by paleoceanographers to reconstruct aspects of past coastal climate. This report focuses on the end of the "Little Ice Age" (15th to 19th century) and on the beginning of this century, a period known to encompass extreme climate excursions and weather events in the Santa Barbara Basin and other parts of Southern California. El Niño events are known to disrupt Southern California's coastal ecosystems and to cause anomalous weather conditions, but El Niño events in Southern California before 1990 have been largely undocumented.