Search

An investigation of the iron (Fe) perturbations needed to stimulate diatom production requires an assessment of the lowest Fe concentration whereby uptake still allows maximum cellular growth rates and of what Fe flux to surface waters is then required to sustain high diatom productivity once the concentration threshold is exceeded. Research in this area has concluded that climate forcing has definitely had an impact on productivity in the eastern equatorial Pacific. Furthermore, equatorial sediment records give an insight into these impacts. However, some element of this cycling may have been fuelled by localized tectonic processes in the Papua New Guinea island-arc area.

There are connections between apparent spatial shifts in the skipjack tuna population in the Pacific Ocean and large zonal displacements of the western equatorial Pacific warm pool that take place during El Nino Southern Oscillation (ENSO) events. Observations of skipjack relative abundance were correlated with a proxy for location of the zone of convergence of surface-layer water masses on the eastern edge of the western Pacific warm pool, the 29 degrees C sea surface temperature isotherm, and with the southern oscillation index.

An iron-enrichment experiment in the equatorial Pacific Ocean sparked an enormous phytoplankton bloom which consumed large amounts of carbon dioxide and nitrate that they cannot fully utilize under normal conditions. This affirms the hypothesis that iron bioavailability restricts phytoplankton growth and biomass in high-nitrate, low-chlorophyll waters, such as the Southern Ocean and the Pacific.

In situ measurements of fluorescence during IronEx II, when dissolved iron was infused into the surface layer of a square patch of ocean in the eastern equatorial Pacific Ocean in 1995, are reported. They show that the iron enrichment induced dramatic biophysical changes of phytoplankton's photosynthetic mechanisms, leading to increased photosynthetic capacities and hence, the massive phytoplankton bloom. Findings offer proof that iron limits the bioavailability of phytoplanktons in high nitrate, low-chlorophyll waters.

A global coupled ocean-atmosphere general circulation model shows an increase in the sea surface temperature (SST) of the tropical Pacific Ocean east of 180 degrees longitude with an increase in atmospheric carbon dioxide. The SST increase is due to cloud albedo feedback, changes in cloud cover, and a decrease in easterly winds and ocean upwelling. The increase is accompanied by anomalies in precipitation and circulation. These changes are similar to observed temperature changes and changes during El Nino events in the tropical Pacific Ocean.

Upwelling waters in the equatorial regions are the main source of iron for biological production in the Pacific Ocean. The increase in sub-nanomolar iron concentration increases the amount of carbon which moves to the deeper waters of the ocean. The rise in iron concentration increases phytoplanktonic growth and biomass. The oceanic biological productivity and carbon export to deeper waters depends on the changes in the water's iron content and the rate of upwelling.

Paleolatitudes from Pacific guyots indicate small latitudinal shifts of Pacific hotspots during the Cretaceous period that differ from the predictions from the true polar wander (TPW) models. The relative motion between Atlantic and Pacific hotspot groups appears to be larger than previously thought, approximately 30 mm per year. Comparison of direct paleolaltitudes with those determined from plate reconstructions facilitate a first-order test of hotspot fixity and TPW. Paleomagnetic data from basal sediments, volcanic basement and flanking sedimentary apron provide statistically inseparable paleolatitudes covering a period of 128-108 Myr.

A large-offset propagating rift in the spreading area of Pacific-Nazca ridge between the Easter and Juan Fernandez microplates reorganizes the plate boundary geometry. A 120 x 120 kilo meters overlap zone exists between the dual active spreading centers due to the fast duelling propagation. This overlapping system is the precursor of a new microplate. There are marked differences between the fossil overlap zones and the present overlap zone.

Viable sediment bacterial groups in five different regions of the Pacific Ocean were found at depths greater than 500 meters. These bacterial groups influence the chemical composition of the atmosphere and the ocean. The selective degradation of organic matter is also caused by these bacterial groups over a large range of geological time. These bacterial distributions and variations in the distribution of bacteria with depth are determined by environmental factors.

Several sediment cores in the eastern equatorial Pacific Ocean point to the occurence of repeated episodes of increased equatorial primary production between 15 and 4.4 million years ago. Thalassiothrix diatom mat deposits appeared as successive laminations covering distances of more than 2,000 km. Their deposition may have overwhelmed the benthos so that their laminations were preserved by physical means.

Comparisons of the iron contained in heterotrophic bacteria and phytoplanktons found in the subarctic region of the Pacific Ocean revealed that the bacteria posses more iron than phytoplanktons. Moreover, heterotrophic bacteria constitute about 20-45% of the biological iron uptake in the region. The results indicate that the bacteria play a crucial role in the biogeochemical cycling of iron.

Spinel-bearing particles found at the Cretaceous/Tertiary boundary at site 577 in the Pacific Ocean appear to result from the impact of a meteor of two km diameter within the Pacific, not from Mexico's Chicxulub crater. Composition and structure of some of the fragments are not consistent with the latter impact site, nor with its distance. This and other studies imply that there were several accretionary impacts at the end of the Cretaceous rather than a single huge one.

Increased availability of iron limits phytoplankton in high nitrate-low chlorophyll regions such as the equatorial Pacific Ocean. Dramatic biological and biogeochemical changes in surface waters of the Pacific Ocean were observed following an in situ iron-fertilization experiment conducted in 1993 and again in 1995. Specifically, it was found that increased availability of the trace nutrient limits cell division rates, abundance and production rate in phytoplankton.

Author Affiliations: Forecasting monsoons and tropical storms can be a challenge, but could be improved for East Asia because the variability of a major atmospheric high-pressure system over the western [...]

Research reveals a dependence between El Nino warm event indices in the Pacific ocean and rainfall and maize yield in Zimbabwe. Model forecasts of the El Nino index precisely predicts maize yield in Zimbabwe a year in advance. This method provides an efficient early-warning system for southern African famines.