An overview of 1000 years of tropical climatic variability from ice cores from the Andes of southern Peru [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Each summer between 1976 and 1984 research was conducted on the Quelccaya Ice Cap with one central objective, to recover an ice core to bedrock from which an approximate 1000 year climatic history for tropical South America could be reconstructed. In 1983 that central objective was accomplished by recovering one core 155 meters in length containing 1350 years and a second core of 163.6 meters containing more than 1500 years of climatic history. ... The most significant climatic event in tropical South America over the last 1500 years was the "Little Ice Age" which is recorded between 1490 to 1880 A.D. in these ice core records. Records from the summit of the Quelccaya Ice Cap show that during the "Little Ice Age" period there was (1) a general increase in particulates (both insoluble and soluble, starting around 1490 A.D. and ending abruptly in 1880 A.D.; (2) an initial increase in net accumulation (1500-1720 A.D.) followed by a period of decreased net accumulation (1720-1860 A.D.); (3) more negative delta-O-18 values beginning in the 1520's and ending around 1880 A.D. The "Little Ice Age" event is evident as a perturbation in all five ice core parameters.

Hydrologic variability related to El Nino in the Pacific Northwest [abstract]

A preliminary statistical analysis was undertaken to evaluate whether the effect of El Nino events is apparent in variables related to hydrologic behavior. Annual precipitation, temperature and streamflow were used for three locations in Oregon representing coastal, Willamette Valley/Cascade and eastern Oregon regions. The mean and variance for periods of El Nino occurrence vs. those with no El Nino were computed. Numerical differences were observed but were not consistent across all stations. The coastal area showed a decrease in mean precipitation and increase in mean streamflow during El Nino events. Other stations showed a positive increase in mean for both precipitation and streamflow for El Nino events. Variance of precipitation was greater in the coastal area but smaller in other areas and vice versa for streamflow during El Nino events. Statistical analyses indicated no significant differences of means, variances or distributions using nonparametric tests for El Nino vs. non-El Nino series.

On the trail of interannual variability in phytoplankton and climate [abstract and figures]

EXTRACT (SEE PDF FOR FULL ABSTRACT): A selective but nontheless real record of phytoplankton activity over the Santa Barbara Basin can be obtained from the underlying varved sediments. The phytoplankton groups preserved are: diatoms (frustrules and spores), silicoflagellates, dinoflagellates (cysts) and coccoliths.

Annual stream flow variability over the western United States [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): The variability of mean annual streamflow over the western United States is described and related to indices of large scale atmospheric circulation over the Pacific Ocean and western U.S. Principal component analysis reveal [sic] four statistically significant modes of streamflow variability across the region.

Subsurface ocean temperature signals on west coast of North America [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Data were extracted from the U.S. Navy Fleet Numerical Oceanographic Center Master Oceanographic Observation Data Set for a 200 km to 300 km wide coastal strip on the west coast of the United States. These data were averaged for the September through February (winter) and March through August (summer) intervals. The resulting winter temperature anomaly values show the El Nino signal in the CCC [Coastal California Current] as positive temperature anomalies from the surface to at least 300 m.

400 years of precipitation variability in central and southern California reconstructed from tree-rings [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Precipitation variability at 31 stations hanging from San Diego to San Francisco and from the coast to the Sierras was characterized ...

Interannual variability of siliceous phytoplankton fluxes and relationships with hydrography in the northeastern subarctic Pacific, 1982-1986 [abstract and figures]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Time-series flux variabilities of biogenic opal particles were measured during 1982-1986 at pelagic Station PAPA (50° N, 145° W) located just south of the Gulf of Alaska, eastern North Pacific. PARFLUX sediment traps with two week sampling increments were deployed at 1000 m and 3800 m in 4200 m deep water, yielding nearly continuous time-series flux records for four years. The flux data allowed us to examine interannual and seasonal variabilities of siliceous phytoplankton production as well as environmental signals retained within the siliceous shells, which can be used to reconstruct environments.

Trends and long-term variability of ocean properties at Ocean Station P in the northeast Pacific Ocean [abstract]

Twenty-seven years (1956-1983) of oceanographic data collected at Ocean Station P (50°N/145°W), as well as supplementary data obtained in its neighborhood, have been examined for trends and interannual variability in the northeast Pacific Ocean. There is evidence that the water is warming and freshening and that the isopycnal surfaces are deepening. Trends in oxyty are mostly not significant. The most common periods for the interannual variability appear to be 2 1/2 and 6-7 years. The vertical movement of water accounts for one half of the changes in temperature and salinity and 30% of those in oxyty. Other factors, such as a shift of water masses, may also be important.

Quantifying intrapopulation variability in stable isotope data for Spotted Seatrout (Cynoscion nebulosus)

Stable isotope (SI) values of carbon (δ13C) and nitrogen (δ15N) are useful for determining the trophic connectivity between species within an ecosystem, but interpretation of these data involves important assumptions about sources of intrapopulation variability. We compared intrapopulation variability in δ13C and δ15N for an estuarine omnivore, Spotted Seatrout (Cynoscion nebulosus), to test assumptions and assess the utility of SI analysis for delineation of the connectivity of this species with other species in estuarine food webs. Both δ13C and δ15N values showed patterns of enrichment in fish caught from coastal to offshore sites and as a function of fish size. Results for δ13C were consistent in liver and muscle tissue, but liver δ15N showed a negative bias when compared with muscle that increased with absolute δ15N value. Natural variability in both isotopes was 5–10 times higher than that observed in laboratory populations, indicating that environmentally driven intrapopulation variability is detectable particularly after individual bias is removed through sample pooling. These results corroborate the utility of SI analysis for examination of the position of Spotted Seatrout in an estuarine food web. On the basis of these results, we conclude that interpretation of SI data in fishes should account for measurable and ecologically relevant intrapopulation variability for each species and system on a case by case basis.

ENSO and precipitation variability over Mexico during the last 90 years

Latin America has been shown to be susceptible to climatic anomalies during El Niño/Southern Oscillation (ENSO) events (eg, Aceituno 1988; Ropelewshi and Halpert 1987; Kiladis and Diaz 1989). While these studies have emphasized ENSO-related rainfall and temperature anomalies over Central and South America, less work has been done on the climatic effects of ENSO over the Mexican region. In this study we are investigating interannual and intraseasonal fluctuation in temperature and precipitation over the southwestern United States and Mexico since the turn of the century. We are particularly interested in the effects of ENSO on the interannual variability over this region. This report focuses on the association between ENSO and interannual variability of precipitation over Mexico.