Planktic Foraminifera-Based Sea Surface Temperature Estimates and Late Quaternary Oceanography off New Zealand's West Coast

10.26686/wgtn.16985332 ◽

2021 ◽

Author(s):

◽

Andrew Peter Kolodziej

Keyword(s):

New Zealand ◽

Surface Water ◽

West Coast ◽

Mass Movement ◽

Sea Surface ◽

Temperate Species ◽

Tasman Sea ◽

Modern Analogue ◽

Neogloboquadrina Dutertrei ◽

Glacial Periods

<p>Planktic foraminiferal assemblages were used to investigate the paleoceanography of the Eastern Tasman Sea over the last 480 kyrs (Marine Isotope Stages 12-1). One hundred and sixty-two faunas (96 picked and identified as part of this project (MIS 12-6) added to 66 census counts from Dr. M. Crundwell (MIS 6-1)) have been assembled from Marion Dufresne piston core MD06-2986 (~43˚ S. off New Zealand‟s west coast, 1477 m water depth). Faunal changes through the last five glacial-interglacial cycles are used to track surface water mass movement. Glacial periods are dominated by the eutrophic species Globigerina bulloides, with significant contributions from the temperate species Globoconella inflata. Temperate species Neogloboquadrina incompta and Gc. inflata dominate interglacials, with the former dominating the warmer parts and the latter dominating the cooler parts of the interglacials. Modern Analogue Technique (MAT) and an Artificial Neural Network (ANN) were used to estimate past sea surface temperatures (SST) based on the foraminiferal census counts data (23 species, ~46,000 specimens). SSTs show that MIS 12 was the longest, sustained cold period, while the coldest temperature was recorded in MIS 5d (~8º C). Interglacials MIS 11 and 5e are the two warmest stages of the record, with SSTs reaching ~18.5º C, about ~2º C warmer than present day. We find that contrary to either the western Tasman Sea or offshore eastern New Zealand, the eastern Tasman Sea has been fairly isolated from any major influx of subpolar or subtropical species carried in with surface water from either high or low latitude sources. Subtropical taxa abundance (Globigerinoides ruber, Neogloboquadrina dutertrei (D), Globigerinoides sacculifer, Globigerinella aequilateralis, Sphaeroidinellopsis dehiscens, Truncorotalia truncatulinoides (D), Beella digitata) is low (average ~0.6%) and only prominent during peak interglacials. Subantarctic taxa abundance (Neogloboquadrina pachyderma, Neogloboquadrina dutertrei (S)) is low (average ~5.1%), but significant, particularly in glacial periods. Comparison of faunal and SSTANN data along with ratios of Nq. pachyderma:Nq. incompta (previously referred to as coiling ratios of Nq. pachyderma) and absolute abundance of planktic productivity (a productivity proxy) suggest that the STF migrated northwards towards the site in all glacial periods, and may have moved over the site in MIS 12 and possibly MIS 5d. A latitudinal SSTANN 25 comparison between offshore eastern and western New Zealand reveals that MD06-2986 (~43º S) is most similar (~0.5º C) to ODP Site 1125 (~42º S). On the contrary, ODP Site 1119 (44º S) is ~5º C cooler than MD06-2986. This comparison highlights the significant changes in surface water masses off eastern New Zealand that exist in such a short span of latitude because of the influence of a complex submarine topography.</p>

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Qualitative and quantitative reconstruction of surface water characteristics and recent hydrographic changes in the Trondheimsfjord, central Norway

Climate of the Past Discussions ◽

10.5194/cpd-9-4553-2013 ◽

2013 ◽

Vol 9 (4) ◽

pp. 4553-4598 ◽

Cited By ~ 2

Author(s):

G. Milzer ◽

J. Giraudeau ◽

S. Schmidt ◽

F. Eynaud ◽

J. Faust

Keyword(s):

Surface Water ◽

Sea Surface ◽

Surface Mixed Layer ◽

210Pb And 137Cs ◽

The North ◽

Water Characteristics ◽

Run Off ◽

Modern Analogue ◽

The North Atlantic Oscillation ◽

The Impact

Abstract. In the present study we investigate dinocyst assemblages in the Trondheimsfjord over the last 25 to 50 yr from three well-dated multi-cores (210Pb and 137Cs) retrieved along the fjord axis. The downcore distribution of the cysts is discussed in view of changes of the key surface water parameters sea-surface temperatures (SSTs) and sea-surface salinities (SSSs) monitored in the fjord, as well as river discharges. We examine the impact of the North Atlantic Oscillation pattern and of waste water supply from the local industry and agriculture on the fjord ecological state and hence dinocyst species diversity. Our results show that dinocyst production and diversity in the fjord is not evidently affected by human-induced eutrophication. Instead the assemblages appear to be mainly controlled by the NAO-related changes in physico-chemical characteristics of the surface mixed layer. Still, discharges of major rivers were modulated, since 1985 by the implementation of hydropower plants which certainly influences the freshwater and nutrient supply into the fjord. The impact, however, is variable according to the local geographical setting, and barely differentiated from natural changes in river run off. We ultimately test the use of the modern analogue technique (MAT) for the reconstruction of winter and summer SSTs and SSSs and annual primary productivity (PP) in this particular fjord setting. The reconstructed data are compared with time-series of SSTs and SSSs measured at 10 m water depth, as well as with mean annual PPs along the Norwegian coast and within Scandinavian fjords. The reconstructions are in general good agreement with the instrumental measurements and observations from other fjords. Major deviations can be addressed to peculiarities in the assemblages linked to the particular fjord setting and the related hydrological structure.

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Large-scale influence of the New Zealand seafloor topography on western boundary currents of the South Pacific Ocean.

Marine and Freshwater Research ◽

10.1071/mf9850001 ◽

1985 ◽

Vol 36 (1) ◽

pp. 1 ◽

Cited By ~ 16

Author(s):

RA Heath

Keyword(s):

New Zealand ◽

West Coast ◽

East Coast ◽

South Pacific ◽

Surface Flow ◽

Current Speed ◽

Western Boundary ◽

East Australian Current ◽

South Pacific Ocean ◽

Tasman Sea

The extensive New Zealand submarine platform lying approximately 1600 km east of Australia has a strong influence on the South Pacific circulation. Together with the Kermadec Ridge, it is the western boundary of the deep South Pacific Ocean with an associated deep western boundary current. Although New Zealand probably influences where the East Australian Current separates from the east Australian coast, at the latitude of northernmost New Zealand, the sloping seafloor on the New Zealand west coast does allow for a meridional flow there. However, the decrease in current speed with depth does decrease the influence of the bottom topography. The net result is that there is both an intensification of the zonal flow across the Tasman Sea at the latitude of northernmost New Zealand, the speed of which is enhanced by the flow over the extensive ridge system, and a general eastwards flow in the Tasman Sea over the latitudinal range of New Zealand, which feeds meridional flows on the New Zealand west coast. It is suggested that the general west to east flow past New Zealand restricts the westward propagation of second- and higher-order baroclinic Rossby waves with the result that, whereas the East Australian Current has rapid near-surface flow which decreases rapidly with depth in the upper 500 m, the surface flow on the east coast of New Zealand is less rapid and decreases more uniformly with depth. One possible consequence of the current speed change with depth is that the flow and eddies on the New Zealand east coast appear to be influenced by the bathymetry whereas the East Australian Current eddies are more a primary component of the current linked to instability in the current system.

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Re-envisioning the structure of last glacial vegetation in New Zealand using beetle fossils

Quaternary Research ◽

10.1016/j.yqres.2007.03.009 ◽

2007 ◽

Vol 68 (1) ◽

pp. 121-132 ◽

Cited By ~ 15

Author(s):

Philip I. Burge ◽

James Shulmeister

Keyword(s):

New Zealand ◽

West Coast ◽

Coastal Vegetation ◽

Woody Vegetation ◽

Dune Field ◽

South West ◽

Tussock Grassland ◽

Beetle Assemblages ◽

Closed Canopy ◽

Glacial Periods

AbstractA series of 18 fossil beetle assemblages are used to reconstruct the paleoenvironment of the northwest West Coast, New Zealand, over the period of the last interstadial–stadial transition (ca. 37,000–21,300 cal yr BP). The samples were recovered from an in-filled hollow within a dune field ca. 9 km south west of Westport (41°47′S, 171°30′E). This fossil beetle reconstruction is compared to an existing palynological reconstruction from the same site. The beetle assemblages indicate an environment of marshy shrubland interspersed with closed canopy coastal vegetation prior to glacial onset, and a mosaic of closed canopy patches and open tussock grassland during full glacial conditions. These interpretations, contrast with the palynologically based interpretation which indicates subalpine shrubland prior to glacial onset and widespread grassland with little woody vegetation during the period of maximum glacial cooling. This study is consistent with other non-pollen studies in New Zealand and indicates that the palynological interpretation of the paleoenvironment of the Westport region downplays the importance of closed canopy vegetation in the area during the transition from interstadial to full glacial (stadial) conditions. It challenges the interpretation of open vegetation at low elevations during glacial periods from pollen studies.

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Seasonal variation of surface water CO2 partial pressure in the Southland Current, east of New Zealand

Marine and Freshwater Research ◽

10.1071/mf98115 ◽

1999 ◽

Vol 50 (5) ◽

pp. 375 ◽

Cited By ~ 13

Author(s):

Kim I. Currie ◽

Keith A. Hunter

Keyword(s):

Biological Activity ◽

New Zealand ◽

Surface Water ◽

Partial Pressure ◽

Surface Waters ◽

Sea Surface ◽

Mixing Processes ◽

Co2 Partial Pressure ◽

Partial Pressure Of Co2 ◽

Effects Of Temperature

The partial pressure of CO2 in the surface waters (pCO2sw) of the Southland Front east of New Zealand was determined over one annual cycle in 1992/93. Associated parameters of temperature, salinity and nutrients were also measured. Both the modified subtropical waters of the Southland Current and the cooler subantarctic surface waters were undersaturated with CO2 with respect to the atmosphere. The maximum ΔpCO2 of –150 µatm was measured in April 1993. A simple model taking into account the effects of temperature, biological activity and air–sea exchange applied to subantarctic surface water indicated that at different times of the year changes in sea surface temperature, biological activity and mixing processes are the dominant controls of pCO2sw .

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