Graeme Wells

Large-scale reorganization of ocean currents offshore Western Australia during the Late Quaternary

Abstract The history of coastal surface currents in the eastern Indian Ocean over the last ∼ 130 kyr has been studied through the application of the FI-2 transfer function to planktic foraminifera in deep-sea cores in a N-S transect offshore Western Australia. The concept of sea-surface temperature (SST) gradient residuals is the amount by which the sea-surface temperature gradient of a given time differs from that in the modern sea. The SST gradient residuals for several episodes of climate extremes in the Late Quaternary [the last glacial maximum (∼ 20 kyr B.P.), the last interglacial maximum ( ∼ 122-120 kyr B.P.), and at the end of the penultimate glaciation ( ∼ 130 kyr B.P.)] indicate that areas north of ∼ 18°S off Western Australia have changed very little during the extremes in climate over the last ∼ 130 kyr, while south of ∼ 18°S there have been significant changes in surface-water temperatures. Large areas of anomalously cool surface-water were established off North West Cape (22°S–24°S) during both glacial and interglacial extremes. These reflect the increased influence of the West Australian current on the surface-water circulation. During the last glacial maximum and at the end of the penultimate glaciation, cold sea-surface temperature anomalies were established near to the coast, indicating that the Leeuwin Current did not warm the coastal zone as it does today. During the last interglacial maximum the Leeuwin Current flowed as an intensified current in a narrow zone close to the coast, but did not significantly warm surface-waters offshore as far as 20°–25°S, where a zone of cold water was maintained.

Response of deep-sea benthic foraminifera to Late Quaternary climate changes, southeast Indian Ocean, offshore Western Australia

The Late Quaternary benthic foraminifera of four deep-sea cores off Western Australia (ODP 122–760A, ODP122–762B, BMR96GC21 and RC9–150) have been examined for evidence of increased surface productivity to explain the anomalously low sea-surface paleotemperatures inferred by planktic foraminifera for the last and penultimate glaciations. The δ13C trends ofCibicidoides wuellerstorfi, and differences between the δ13C trends of planktics (Globigerinoides sacculifer) and benthicsC. wuellerstorfi) in the four cores indicate that during stage 6 bottom waters were significantly depleted in δ13C, and strong δ13C gradients were established in the water column, while during stage 2 and the Last Glacial Maximum, δ13C trends did not differ greatly from that of the Holocene. Two main assemblages of benthic foraminifera were identified by principal component analyses: one dominated byUvigerina peregrina, another dominated byU. proboscidea. Abundance of these Uvigerinids, and of taxa preferring an infaunal microhabitat, and ofEpistominella exigua andBulimina aculeata indicate that episodes of high influx of particulate organic matter were established in most sites during glacial episodes, and particularly so during stage 6, while evidence for upwelling during the Last Glacial Maximum is less strong. The Penultimate Glaciation upwellings were established within the areas of low sea-surface paleotemperature indicated by planktic foraminifera. During the Last Interglacial Climax, upwelling appears to have been established in an isolated region offshore from a strengthened Leeuwin Current off North West Cape. Last Glacial Maximum δ13C values ofC. wuellerstorfi at waterdepths of less than 2000 m show smaller than global mean glacial-interglacial changes suggesting the development of a deep hydrological front. A similar vertical stratification/bathyal front was also established during the Penultimate Glaciation.

Growth and the Current Account in a Small Open Economy

Abstract The authors provide a framework with which to analyze growth in a small economy with perfect capital mobility. The framework provides a diagrammatic representation of steady states that differs in interesting and important ways from the usual closed-economy Solow-Swan diagram. The authors use the key diagrams to illustrate the effects of changes in parameters such as the saving rate and productivity growth on steady-state values of macroeconomic aggregates. They compare the steady-state results for the open economy with those obtained using the more familiar closed-economy model. They illustrate the possibility of endogenous income growth.

Teaching Aggregate Demand and Supply Models

The author analyzes the inflation-targeting model that underlies recent textbook expositions of the aggregate demand–aggregate supply approach used in introductory courses in macroeconomics. He shows how numerical simulations of a model with inflation inertia can be used as a tool to help students understand adjustments in response to demand and supply shocks of various kinds.

Pierce and Haugh on Characterizations of Causality A Re-examination

Abstract This paper amends the set of equivalent necessary and sufficient conditions under which y does not cause x, provided by Pierce and Haugh (1977).

The transmission of economic activity: Evidence for the U.S. and its trading partners

Abstract This paper assesses empirical evidence bearing on the nature of the mechanism by which economic activity is transmitted from the US to its small trading partners. The cross-spectral analysis gives mixed results, but provides some support for a ‘Keynesian’ view.