Circulation over the northeastern New Zealand continental slope, shelf and adjacent Hauraki Gulf, during spring and summer

Zeldis, John; Walters, Roy A.; Greig, Malcolm J.; Image, Katie

doi:10.1016/j.csr.2003.11.007

Cited by 66 publications

(94 citation statements)

References 16 publications

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“…Upwelling on the NE shelf has been correlated to seasonal wind forcing in November and December (Zeldis et al, 2004). However, by the Austral Autumn (i.e., Feburary), shelf dynamics have switched to downwelling with strong stratification separating the shelf from shallower coastal waters.…”

Section: Field Setting: Firth Of Thames-hauraki Gulfmentioning

confidence: 99%

“…This behavior is most clearly captured by larger near-bed residual flows (Figure 6). Fluctuations between upwelling and downwelling conditions during the summer months occur in outer Hauraki Gulf (Zeldis et al, 2004), which has elsewhere been associated with up-slope propagation of bottom boundary layers (i.e., Perlin et al, 2005). The presence of near-bed landward intrusions of homogeneous density oceanic water are important when evaluating exchange processes controlling material transport.…”

Section: Annual Cyclementioning

confidence: 99%

“…The same was observed during autumn 2013 with weak vertical gradients over the water column. Vertical temperature gradients were largest, unsurprisingly, during mid-summer when surface heating enhances vertical stratification in the Firth-HG system (Zeldis et al, 2004). Dominant timescales over the year were determined in the frequency domain for surface and near-bed ADCP observations (Figure 4).…”

Section: The Annual Cyclementioning

confidence: 99%

“…The first freshwater buoyancy input for the winter during July 2012. The third discharge event was from October 2013 when discharges coincided with the timing of biophysical responses in the system (i.e., Zeldis et al, 2004) and persistent spring winds (Figures 2A,B). Figure 2 show the timing of the three events.…”

Section: Salinity Responses After Discharge Eventsmentioning

confidence: 99%

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Evaluating the Surface Response of Discharge Events in a New Zealand Gulf-ROFI

O'Callaghan

Stevens

2017

Front. Mar. Sci.

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Using moorings with a surface expression, responses of buoyant river outflows were examined in the Firth-Hauraki Gulf system, New Zealand. The Firth region of freshwater influence (ROFI) behaves as a gulf-type ROFI where the balance of key processes lies between rotation and advection. The latter process is largely regulated by the frequency and amplitude of freshwater discharges. Using 12-months of observations from two inner Firth sites, the system was found to be salinity stratified for up to 4 months of a year. During the largest event (274 m 3 s −1 , mean daily maximum) in 2012 near-oceanic surface salinity (34 psu) freshened substantially down to 28 psu over the upper 3 m. Time lags between freshwater inflows and ROFI response were 4 and 7 days at the Waiheke and WilsonB locations, respectively. Faster seaward advection of surface layers occurred for a minimum of 3 days and up to a week after peak discharges. High frequency winds (∼3-hourly) were persistent in regulating surface flows over the annual cycle. Surface salinity had peaks in energy that were coherent with surface flows at periods of 16-32 days over the Austral winter. The duration of discharge events was O(days), yet responses by buoyancy and advection were evident for weeks to a month in the Firth ROFI.

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Section: Field Setting: Firth Of Thames-hauraki Gulfmentioning

confidence: 99%

Section: Annual Cyclementioning

confidence: 99%

Section: The Annual Cyclementioning

confidence: 99%

Section: Salinity Responses After Discharge Eventsmentioning

confidence: 99%

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Evaluating the Surface Response of Discharge Events in a New Zealand Gulf-ROFI

O'Callaghan

Stevens

2017

Front. Mar. Sci.

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“…1), so along-shelf wind components were calculated by adding 30°to the raw bearings to align the u and v components of the velocity cross-shelf and along-shelf, respectively. Along-shelf wind stresses (τ as ) were calculated (Zeldis et al 2004) as:( 1) where p a = 1.3 kg m -3 is the air density, u w and v w are the components of the wind vector in the cross-shelf and along-shelf directions, respectively, and c d , the surface drag coefficient, is related to the wind speed, w, by:Note that in the convention applied in the present study, negative values indicate wind stress blowing from the NNW, and positive values indicate stress blowing from the SSE.Sea surface temperatures were obtained using satellite radiometer data (NIWA SST Archive; Uddstrom & Oien 1999) from monthly means of a 3-by-3 pixel array centred on 40.90°S, 174.19°E, at the entrance to Pelorus Sound (Fig. 1), starting in January 1993.…”

mentioning

confidence: 99%

ENSO and riverine control of nutrient loading, phytoplankton biomass and mussel aquaculture yield in Pelorus Sound, New Zealand

Zeldis¹,

Howard‐Williams²,

Carter³

et al. 2008

Mar. Ecol. Prog. Ser.

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Multi-year time-series were used to describe oceanic and riverine nutrient supply and primary biomass in Pelorus Sound, a 50 km long estuary supporting most of New Zealand's $ 200 million per annum mussel Perna canaliculus aquaculture industry. In the summer half-year (October to March), when the Southern Oscillation Index (SOI) was negative (El Niño), NNW along-shelf wind stress strengthened and sea surface temperature (SST) at the Sound entrance cooled, indicating upwelling. This triggered increases in phytoplankton biomass, particulate nitrogen (PN) and per capita yield of farmed mussels in the Sound. In the winter half-year (April to September), wind stress was unrelated to SOI, but during NNW winds Pelorus River flows increased, along with NO 3 -, phytoplankton biomass, PN and mussel yield. During an extended period of positive SOI (La Niña), SSE winds and drought during 1999 to 2002, seston (PN) abundance and its food quality decreased, concomitant with a mussel yield decrease of ~25% throughout Pelorus Sound. Seston and mussel yield had recovered by 2003 without reductions in farming intensity, so over-grazing by mussels did not cause the yield minimum. Instead, climatic forcing of oceanic and riverine N supply and seston biomass underlay the inter-annual variation in mussel yield. As tracers of the relationship of nutrient loading and production, PN and mussel yield appeared more reliable than NO 3 -or chl a concentrations. In Pelorus Sound, oceanic and riverine N supplies are seasonally complementary and sustain year-round mussel yield, although their inter-annual variability, linked to wider climate forcing, can drive considerable fluctuation in yield over the decadal scale. KEY WORDS: Climate · Estuaries · Mussel aquaculture · ENSO · Nutrients · Primary biomass Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 371: [131][132][133][134][135][136][137][138][139][140][141][142] 2008 Figueiras et al. 2002, Huang et al. 2008. These potentially confounding effects mean that it is important to have a good understanding of factors affecting estuarine productivity to enable the aquaculture industry and resource managers to separate natural climatic variability from impacts due to the farming activity itself.As a case in point, here we consider Pelorus Sound, New Zealand (see Fig. 1). This estuary supports ca. 3 ⁄ 4 of the $ 200 million per annum, 75 000 t green weight, national production of New Zealand greenshell mussels Perna canaliculus, which are grown on hundreds of individual farms throughout its main channel, sidearms and embayments (New Zealand Marine Farming Association 2007). The mussels are grown using suspended rope culture (Zeldis et al. 2005) and feed on phytoplankton and other suspended particles drifting through the farms. Starting in early 1999, farm productivity in the Sound declined by ca. 25% (measured in terms of per capita meat yield) followed by recovery during 2002, with substantial economic impacts and distortions within the in...

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Southwest Pacific subtropics responded to last deglacial warming with changes in shallow water sources

et al. 2014

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This study examined sources of mixed layer and shallow subsurface waters in the subtropical Bay of Plenty, New Zealand, across the last deglaciation (~30-5 ka). C depletion of~0.3‰ suggests that deeper subsurface waters had a delayed reaction to changing conditions during the deglaciation. This contrasts with the isotopic records from nearby Hawke Bay, to the east of the North Island of New Zealand, which exhibited several changes in thermocline depth indicating switches between distal subtropical and proximal subantarctic influences during the early deglaciation ending only after the Antarctic Cold Reversal. Our results identify the midlatitude subtropics, such as the area around the North Island of New Zealand, as a key region to decipher high-versus low-latitude influences in Southern Hemisphere shallow water masses.

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Circulation over the northeastern New Zealand continental slope, shelf and adjacent Hauraki Gulf, during spring and summer

Cited by 66 publications

References 16 publications

Evaluating the Surface Response of Discharge Events in a New Zealand Gulf-ROFI

Evaluating the Surface Response of Discharge Events in a New Zealand Gulf-ROFI

ENSO and riverine control of nutrient loading, phytoplankton biomass and mussel aquaculture yield in Pelorus Sound, New Zealand

Southwest Pacific subtropics responded to last deglacial warming with changes in shallow water sources

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