The Subtropical Convergence east of New Zealand

Abstract

Hydrographic data from the region of the Subtropical Convergence east of New Zealand between 177°E and 179°E show that in spring the convergence occurs near the Chatham Rise. North of the Chatham Rise the structure is fairly regular with isolines of temperature and salinity sloping upwards towards the south. To the south of the Chatham Rise the structure is more complex with an apparent intrusion of Subtropical Water into the Subantarctic Water below depths of about 150 m.

Glacial‐interglacial sea surface temperature changes across the subtropical front east of New Zealand based on alkenone unsaturation ratios and foraminiferal assemblages

“…These sediment core top temperatures largely reflect the modern temperature gradient across the front of ∼4°C with each technique being internally consistent and in agreement with hydrological studies from the immediate area of the cores [ Chiswell , 1994; Garner , 1967; Gilmour and Cole , 1979]. The alkenone‐derived values suggest a greater temperature difference across the front of 4.7°C, in agreement with summer observational data, whereas the foraminiferal gradient of 3.4°C is more indicative of spring or fall conditions (Figure 6c) [ Chiswell , 1994].…”

“…The U 37 K ′ core top SST estimate of 17°C in core W268 reflects its more proximal location relative to the front. The average of 18.4°C for the two core top U 37 K ′ SST values from north of the rise agrees well with the summer SST in subtropical waters in the area (Figures 3 and 4) [ Chiswell , 1994; Garner , 1967; Gilmour and Cole , 1979]. South of the front, core U939 sits on the southern flank of the rise and the southern edge of the seasonal range of the STF, while core U938 sits farther south on the flat of the Bounty Trough well to the south of the STF.…”

“…High‐resolution short‐term studies, although lacking the advantage of multiyear averaging, provide more realistic across‐front temperature profiles [e.g., Belkin and Gordon , 1996; Chiswell , 1994; Garner , 1967; Gilmour and Cole , 1979; Uddstrom and Oien , 1999]. Chiswell [1994] presents monthly mean temperatures for 1989–1990 calculated from satellite images which agree well with the hydrocast data from summer 1963 and spring 1976 [ Garner , 1967; Gilmour and Cole , 1979]. Comparison of data of Chiswell [1994]; Levitus [1984]; Levitus and Boyer [1994]; and COADS [1999] indicates that Levitus data underestimate summer temperatures in the area of our northern cores by up to 2°C and tend to underestimate summer temperatures by up to 1°C at our southern sites (Figures 3 and 6).…”

A hydrodynamic model of Chatham Rise, New Zealand

“…Chatham Rise oceanography the physical oceanography of the Chatham Rise region has been studied by a number of authors (e.g., Gilmour & Cole 1979;Bradford-Grieve et al 1991;Chiswell 2002aChiswell , 2003Chiswell , 2005sutton 2001 and summarised pictorially in a chart (Carter et al 1998).…”

“…1995;Belkin& Gordon 1996). To the east of New Zealand the STF is located over the Chatham Rise and is relatively narrow (c. 150 km) and limited in the vertical by the shallow bathymetry (Gilmour & Cole 1979;Heath 1981;Sutton 2001;Chiswell 2002a).…”