90 results on '"Stephen M. Chiswell"'
Search Results
2. Trace Metal Dynamics in Shallow Hydrothermal Plumes at the Kermadec Arc
- Author
-
Charlotte Kleint, Rebecca Zitoun, René Neuholz, Maren Walter, Bernhard Schnetger, Lukas Klose, Stephen M. Chiswell, Rob Middag, Patrick Laan, Sylvia G. Sander, and Andrea Koschinsky
- Subjects
trace metals ,hydrothermal plumes ,South Pacific Ocean ,plume dispersion ,arc hydrothermalism ,Macauley volcano ,Science ,General. Including nature conservation, geographical distribution ,QH1-199.5 - Abstract
Hydrothermal vents are a source of many trace metals to the oceans. Compared to mid-ocean ridges, hydrothermal vent systems at arcs occur in shallower water depth and are much more diverse in fluid composition, resulting in highly variable water column trace metal concentrations. However, only few studies have focused on trace metal dynamics in hydrothermal plumes at volcanic arcs. During R/V Sonne cruise SO253 in 2016/2017, hydrothermal plumes from two hydrothermally active submarine volcanoes along the Kermadec arc in the Southwest Pacific Ocean were sampled: (1) Macauley, a magmatic dominated vent site located in water depths between 300 and 680 m, and (2) Brothers, located between 1,200 and 1,600 m water depth, where hydrothermalism influenced by water rock interactions and magmatically influenced vent sites occur near each other. Surface currents estimated from satellite-altimeter derived currents and direct measurements at the sites using lowered acoustic Doppler current profilers indicate the oceanic regime is dominated by mesoscale eddies. At both volcanoes, results indicated strong plumes of dissolved trace metals, notably Mn, Fe, Co, Ni, Cu, Zn, Cd, La, and Pb, some of which are essential micronutrients. Dissolved metal concentrations commonly decreased with distance from the vents, as to be expected, however, certain element/Fe ratios increased, suggesting a higher solubility of these elements and/or their stronger stabilization (e.g., for Zn compared to Fe). Our data indicate that at the magmatically influenced Macauley and Brothers cone sites, the transport of trace metals is strongly controlled by sulfide nanoparticles, while at the Brothers NW caldera wall site iron oxyhydroxides seem to dominate the trace metal transport over sulfides. Solution stabilization of trace metals by organic complexation appears to compete with particle adsorption processes. As well as extending the generally sparse data set for hydrothermal plumes at volcanic arc systems, our study presents the first data on several dissolved trace metals in the Macauley system, and extends the existing plume dataset of Brothers volcano. Our data further indicate that chemical signatures and processes at arc volcanoes are highly diverse, even on small scales.
- Published
- 2022
- Full Text
- View/download PDF
3. The periodical cicada four-year acceleration hypothesis revisited and the polyphyletic nature of Brood V, including an updated crowd-source enhanced map (Hemiptera: Cicadidae: Magicicada)
- Author
-
John R. Cooley, Nidia Arguedas, Elias Bonaros, Gerry Bunker, Stephen M. Chiswell, Annette DeGiovine, Marten Edwards, Diane Hassanieh, Diler Haji, John Knox, Gene Kritsky, Carolyn Mills, Dan Mozgai, Roy Troutman, John Zyla, Hiroki Hasegawa, Teiji Sota, Jin Yoshimura, and Chris Simon
- Subjects
Periodical Cicada ,Distribution ,Mapping ,Climate ,Biogeography ,mtDNA ,Medicine ,Biology (General) ,QH301-705.5 - Abstract
The periodical cicadas of North America (Magicicada spp.) are well-known for their long life cycles of 13 and 17 years and their mass synchronized emergences. Although periodical cicada life cycles are relatively strict, the biogeographic patterns of periodical cicada broods, or year-classes, indicate that they must undergo some degree of life cycle switching. We present a new map of periodical cicada Brood V, which emerged in 2016, and demonstrate that it consists of at least four distinct parts that span an area in the United States stretching from Ohio to Long Island. We discuss mtDNA haplotype variation in this brood in relation to other periodical cicada broods, noting that different parts of this brood appear to have different origins. We use this information to refine a hypothesis for the formation of periodical cicada broods by 1- and 4-year life cycle jumps.
- Published
- 2018
- Full Text
- View/download PDF
4. Mesoscale eddies and the impact of coastal iron supply on primary production in the South Pacific Subtropical Front
- Author
-
Stephen M. Chiswell, Philip W. Boyd, Sylvia G. Sander, Michael J. Ellwood, and Angela Milne
- Subjects
Aquatic Science ,Oceanography - Abstract
Highlights • Dissolved iron limits primary production in offshore South Pacific surface waters. • Phytoplankton is elevated in high-iron filaments in mesoscale eddies east of New Zealand. • Iron in these eddies is due to entrainment of high-iron coastal water into offshore water. • The resultant eddy-driven flux of iron supports production in the Subtropical Front. Abstract Subtropical and subantarctic waters either side of the southern hemisphere Subtropical Front are considered iron-limited, suggesting production within the front is dependent on a supply of iron from atmospheric deposition, zonal advection of coastal water, or upwelling. We present the results from a one-day biogeochemical survey in Subtropical Water east of the North Island, New Zealand, in a region where mesoscale cyclonic and anticyclonic eddies entrain chlorophyll in filaments around the eddies. There was no significant relationship between upper mixed layer chlorophyll and any physical or macronutrient quantity. However, chlorophyll was significantly positively correlated with dissolved iron. A simple model suggests that while vertical entrainment of iron into the upper mixed layer occurred, most of the dissolved iron in the eddy was due to entrainment of high-iron coastal water into low-iron offshore Subtropical Water, and that this iron supports primary production in otherwise iron-deficient water. We suggest that a significant component of the total primary production within the Subtropical Front may be determined by mesoscale eddy induced lateral advection of iron.
- Published
- 2022
5. Seasonal Cycles of Phytoplankton and Net Primary Production from Biogeochemical Argo Float Data in the South-West Pacific Ocean
- Author
-
Stephen M. Chiswell, Andrés Gutiérrez-Rodríguez, Mark Gall, Karl Safi, Robert Strzepek, Moira R. Décima, and Scott D. Nodder
- Subjects
Aquatic Science ,Medio Marino ,Oceanography ,Centro Oceanográfico de Gijón - Abstract
We present annual cycles of chlorophyll a, phytoplankton carbon, nitrate and oxygen for Subtropical (STW), Subantarctic (SAW), and Subantarctic Mode (SAMW) waters near Aotearoa New Zealand from data collected by two Biogeochemical (BGC) Argo floats. We develop two simple models of depth-integrated net primary production (NPP), tuned against 14C-uptake measurements, to compare with Vertically-Generalised Production Model (VGPM) satellite-based estimates of NPP. One model is the simplest possible, and assumes production is proportional to light multiplied by chlorophyll a concentration. The second model modifies the light response profile to account for photoacclimation. In STW at 30–35°S, enhanced production is initiated in austral autumn when the mixed layer deepens to entrain nutrients into the photic zone. For about half the year, there is substantial production within a deep chlorophyll maximum that sits below the mixed layer. Consequently, depth-integrated NPP is only loosely related to surface biomass as imaged from satellite remote-sensing, and BGC Argo-based model estimates of depth-integrated NPP are about double VGPM estimates. In SAW at 45–55°S, production is initiated when vertical mixing decreases in austral spring. Production is largely within the mixed layer, and depth-integrated phytoplankton biomass and depth-integrated NPP follow surface phytoplankton biomass. Model estimates of depth-integrated NPP based on BGC Argo float profiles are comparable with VGPM estimates for the southern water masses., SI
- Published
- 2022
6. The physics of New Zealand’s shelf seas: introduction to the special issue
- Author
-
Stephen M. Chiswell, Joe O’Callaghan, Moninya Roughan, and Craig Stevens
- Subjects
0106 biological sciences ,geography ,geography.geographical_feature_category ,Ecology ,Continental shelf ,010604 marine biology & hydrobiology ,Tropics ,Climate change ,010501 environmental sciences ,Aquatic Science ,Aotearoa ,01 natural sciences ,Oceanography ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences ,Water Science and Technology ,Land mass - Abstract
Aotearoa New Zealand is a marine nation. The islands are 1700 km from the nearest continental land mass, its northern coasts are bathed by warm waters arriving from the tropics, and its southern co...
- Published
- 2021
7. Long-term trends in the frequency and magnitude of upwelling along the West Coast of the South Island, New Zealand, and the impact on primary production
- Author
-
Joanne O’Callaghan and Stephen M. Chiswell
- Subjects
0106 biological sciences ,Ecology ,010604 marine biology & hydrobiology ,Magnitude (mathematics) ,010501 environmental sciences ,Aquatic Science ,01 natural sciences ,Sea surface temperature ,Oceanography ,Upwelling ,Submarine pipeline ,West coast ,Ecology, Evolution, Behavior and Systematics ,Geology ,0105 earth and related environmental sciences ,Water Science and Technology - Abstract
Satellite-derived estimates of sea surface temperature (SST), chlorophyll (Chl), and fluorescence line height (FLH), from 22 sites ∼20 km offshore from the West Coast of the South Island, New Zeala...
- Published
- 2021
8. Relationships between long-term ocean warming, marine heat waves and primary production in the New Zealand region
- Author
-
Philip Sutton and Stephen M. Chiswell
- Subjects
0106 biological sciences ,Ecology ,010604 marine biology & hydrobiology ,Effects of global warming on oceans ,Lead (sea ice) ,Primary production ,010501 environmental sciences ,Aquatic Science ,Heat wave ,01 natural sciences ,Term (time) ,Oceanography ,Primary (astronomy) ,Environmental science ,Production (economics) ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences ,Water Science and Technology - Abstract
We test the paradigm that in a future warmer ocean, shallower winter mixing will lead to less net primary production (NPP), by investigating whether warming between 2002 and 2018 led to changes in ...
- Published
- 2020
9. Off-target capture data, endosymbiont genes and morphology reveal a relict lineage that is sister to all other singing cicadas
- Author
-
M. S. Moulds, Claudio Veloso, Piotr Łukasik, Jeffrey A. Cole, Russell C. Meister, Chris Simon, Michelle L Kortyna, Katherine Nazario, Emily Moriarty Lemmon, Eric R. L. Gordon, Diler Haji, Geert Goemans, Pablo Pessacq, Alan R. Lemmon, Elizabeth J. Wade, John P. McCutcheon, and Stephen M. Chiswell
- Subjects
DEROTETTIX ,0106 biological sciences ,0301 basic medicine ,AMARANTHACEAE ,Lineage (genetic) ,DEROTETTIGINAE ,Morphology (biology) ,PALAEOBIOLOGY ,PHYLOGENOMICS ,Sister ,Biology ,010603 evolutionary biology ,01 natural sciences ,purl.org/becyt/ford/1 [https] ,03 medical and health sciences ,Target capture ,Phylogenomics ,SOUTH AMERICA ,purl.org/becyt/ford/1.6 [https] ,Gene ,Ecology, Evolution, Behavior and Systematics ,ARGENTINA ,SULCIA ,030104 developmental biology ,Evolutionary biology ,ANCHORED HYBRID ENRICHMENT ,HYBRID CAPTURE BYCATCH - Abstract
Phylogenetic asymmetry is common throughout the tree of life and results from contrasting patterns of speciation and extinction in the paired descendant lineages of ancestral nodes. On the depauperate side of a node, we find extant ´relict´ taxa that sit atop long, unbranched lineages. Here, we show that a tiny, pale green, inconspicuous and poorly known cicada in the genus Derotettix, endemic to degraded salt-plain habitats in arid regions of central Argentina, is a relict lineage that is sister to all other modern cicadas. Nuclear and mitochondrial phylogenies of cicadas inferred from probe-based genomic hybrid capture data of both target and non-target loci and a morphological cladogram support this hypothesis. We strengthen this conclusion with genomic data from one of the cicada nutritional bacterial endosymbionts, Sulcia, an ancient and obligate endosymbiont of the larger plant-sucking bugs (Auchenorrhyncha) and an important source of maternally inherited phylogenetic data. We establish Derotettiginae subfam. nov. as a new, monogeneric, fifth cicada subfamily, and compile existing and new data on the distribution, ecology and diet of Derotettix. Our consideration of the palaeoenvironmental literature and host-plant phylogenetics allows us to predict what might have led to the relict status of Derotettix over 100 Myr of habitat change in South America. Fil: Simon, Chris. University of Connecticut; Estados Unidos Fil: Gordon, Eric R. L.. University of Connecticut; Estados Unidos Fil: Moulds, M.S.. Australian Museum Research Institute; Australia Fil: Cole, Jeffrey A.. Pasadena City College; Estados Unidos Fil: Haji, Diler. University of Connecticut; Estados Unidos Fil: Lemmon, Alan R.. Florida State University; Estados Unidos Fil: Lemmon, Emily Moriarty. Florida State University; Estados Unidos Fil: Kortyna, Michelle. Florida State University; Estados Unidos Fil: Nazario, Katherine. University of Connecticut; Estados Unidos Fil: Wade, Elizabeth J.. Curry College. Department of Natural Sciences and Mathematics; Estados Unidos. University of Connecticut; Estados Unidos Fil: Meister, Russell C.. University of Connecticut; Estados Unidos Fil: Goemans, Geert. University of Connecticut; Estados Unidos Fil: Chiswell, Stephen M.. National Institute of Water and Atmospheric Research; Nueva Zelanda Fil: Pessacq, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Centro de Investigación Esquel de Montaña y Estepa Patagónica. Universidad Nacional de la Patagonia "San Juan Bosco". Centro de Investigación Esquel de Montaña y Estepa Patagónica; Argentina Fil: Veloso, Claudio. Universidad de Chile; Chile Fil: McCutcheon, John P.. University of Montana; Estados Unidos Fil: Lukasik, Piotr. University of Montana; Estados Unidos. Swedish Museum of Natural History. Department of Bioinformatics and Genetics; Suecia
- Published
- 2019
10. Physical oceanography of New Zealand/Aotearoa shelf seas – a review
- Author
-
Stephen M. Chiswell, Craig Stevens, Joanne O’Callaghan, and Mark G. Hadfield
- Subjects
0106 biological sciences ,Region of freshwater influence ,Water mass ,Ecology ,010604 marine biology & hydrobiology ,Stratification (water) ,010501 environmental sciences ,Aquatic Science ,Physical oceanography ,Aotearoa ,01 natural sciences ,Oceanography ,Depth contour ,Ecology, Evolution, Behavior and Systematics ,Geology ,0105 earth and related environmental sciences ,Water Science and Technology - Abstract
The shelf seas surrounding New Zealand/Aotearoa, a region nominally extending out to the 250 m depth contour, are complex and varied as they sit above the submerged continent of Zealandia. ...
- Published
- 2019
11. Regional-scale genetic differentiation of the stony coral Desmophyllum dianthus in the southwest Pacific Ocean is consistent with regional-scale physico-chemical oceanography
- Author
-
Lyndsey P. Holland, Ashley A. Rowden, Joanna S. Hamilton, Malcolm R. Clark, Stephen M. Chiswell, and Jonathan P.A. Gardner
- Subjects
Aquatic Science ,Oceanography - Published
- 2022
12. Southern Hemisphere Atmosphere Wavenumber 4 driven Marine Heat Waves and Marine Cool Spells
- Author
-
Stephen M. Chiswell
- Subjects
Atmosphere ,Wavenumber ,Environmental science ,Heat wave ,Atmospheric sciences ,Southern Hemisphere - Abstract
When SST anomalies are defined with respect to a changing baseline and normalised by their 90th percentile, the Tasman Sea is one of the southern hemisphere hotspots of marine heat waves (MHW) and marine cool spells (MCS). There is little evidence that MHW or MCS are increasing in either frequency or intensity, although the duration of MHW has increased from 8 d four decades ago to 26 d now. On average, Tasman Sea MHW/MCS co-occur with MHW/MCS in the Atlantic, Indian, and eastern-Pacific Oceans, in a wavenumber 4 (W4) pattern. Canonical MHW and MCS show they are likely driven by a stalling of the eastward propagation of a W4 atmospheric wave. During MHW, this slow down leads to near-stationary anomalously high and low air pressure areas driving anomalous north-easterly winds over the Tasman Sea. During MCS, similar a slow-down occurs, but shifted by one-half wavelength zonally.
- Published
- 2021
13. The Ocean's Impact on Slow Slip Events
- Author
-
Keisuke Ariyoshi, Joan Gomberg, Emily F. Smith, Stephen M. Chiswell, and P. Baxter
- Subjects
Geophysics ,General Earth and Planetary Sciences ,Slip (materials science) ,Geology ,Seismology - Published
- 2020
14. Exploring mechanisms for spring bloom evolution: contrasting 2008 and 2012 blooms in the southwest Pacific Ocean
- Author
-
Sylvia G. Sander, Karl A. Safi, Philip W. Boyd, Michael J. Ellwood, Robert F. Strzepek, Angela Milne, and Stephen M. Chiswell
- Subjects
0106 biological sciences ,geography ,Chlorophyll a ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Ecology ,010604 marine biology & hydrobiology ,Wind stress ,Context (language use) ,Aquatic Science ,Spring bloom ,01 natural sciences ,Pacific ocean ,Algal bloom ,chemistry.chemical_compound ,Oceanography ,chemistry ,13. Climate action ,Spring (hydrology) ,Environmental science ,14. Life underwater ,Bloom ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences - Abstract
Observations from two research cruises made in 2008 and 2012 to east of New Zealand are put into context with satellite data to contrast and compare surface chlorophyll a evolution in the two years in order to explore mechanisms of phytoplankton bloom development in the southwest Pacific Ocean. In 2008, surface chlorophyll a largely followed the long-term climatological cycle, and 2008 can be considered a canonical year, where the autumn bloom is triggered by increasing vertical mixing at the end of summer and the spring bloom is triggered by decreasing vertical mixing at the end of winter. In contrast, 2012 was anomalous in that there was no autumn bloom, and in early spring there were several periods of sustained increase in surface chlorophyll a that did not become fully developed spring blooms. (In this region, we consider spring blooms to occur when surface chlorophyll a exceeds 0.5 mg m-3). These events can be related to alternating episodes of increased or decreased vertical mixing. The eventual spring bloom in October was driven by increased ocean cooling and wind stress (i.e. increased mixing) and paradoxically was driven by mechanisms considered more appropriate for autumn rather than spring blooms.
- Published
- 2018
15. Evolution of long larval life in the Australasian rock lobster Jasus edwardsii
- Author
-
Stephen M. Chiswell and John D. Booth
- Subjects
0106 biological sciences ,Larva ,010504 meteorology & atmospheric sciences ,Ecology ,biology ,010604 marine biology & hydrobiology ,Jasus edwardsii ,Aquatic Science ,biology.organism_classification ,01 natural sciences ,Fishery ,Ecology, Evolution, Behavior and Systematics ,Geology ,0105 earth and related environmental sciences - Published
- 2017
16. Evolution and Geographic Extent of a Surprising Northern Disjunct Population of 13-Year Cicada Brood XXII (Hemiptera: Cicadidae,Magicicada)
- Author
-
Chris Simon, Teiji Sota, Jin Yoshimura, Dan Mozgai, John R. Cooley, Roy Troutman, Stephen M. Chiswell, Gene Kritsky, and Satoshi Kakishima
- Subjects
0106 biological sciences ,education.field_of_study ,Population ,Zoology ,Biology ,Disjunct ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,Hemiptera ,Brood ,010602 entomology ,Insect Science ,education ,Ecology, Evolution, Behavior and Systematics - Published
- 2017
17. Wind-driven upwelling and surface chlorophyll blooms in Greater Cook Strait
- Author
-
Matthew H. Pinkerton, Mark G. Hadfield, John Zeldis, and Stephen M. Chiswell
- Subjects
0106 biological sciences ,geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Ecology ,010604 marine biology & hydrobiology ,Shoal ,Aquatic Science ,01 natural sciences ,Wind driven ,chemistry.chemical_compound ,Oceanography ,Nutrient ,Water column ,chemistry ,Chlorophyll ,Upwelling ,Ecology, Evolution, Behavior and Systematics ,Geology ,0105 earth and related environmental sciences ,Water Science and Technology - Abstract
We present the results of a combined observational and numerical study to investigate cool plumes of nutrient-rich upwelled water that emanate near the Kahurangi Shoals and extend into Greater Cook Strait. Surface temperature and chlorophyll are mapped using satellite observations to produce surface climatologies, to validate a numerical simulation and to show the utility of using spatial temperature differences as a measure of upwelling. We find upwelling near the Kahurangi Shoals is strongly wind-driven in the weather band. Upwelling occurs at all times of the year, but its surface signature is only visible in summer months. The upwelled nutrient-rich water supports increased primary production compared to surrounding waters, particularly in summer when the water column is more stratified and surrounding surface waters are presumably nutrient depleted.
- Published
- 2016
18. Mean Velocity Decomposition and Vertical Eddy Diffusivity of the Pacific Ocean from Surface GDP Drifters and 1000-m Argo Floats
- Author
-
Stephen M. Chiswell
- Subjects
0106 biological sciences ,Surface (mathematics) ,Dynamic height ,Global Drifter Program ,010504 meteorology & atmospheric sciences ,Meteorology ,010604 marine biology & hydrobiology ,Ocean current ,Wind stress ,Oceanography ,Geodesy ,01 natural sciences ,Eddy diffusion ,Ekman velocity ,Geology ,Argo ,0105 earth and related environmental sciences - Abstract
With the relatively recent development of Global Drifter Program (GDP) drifters that measure the near-surface ocean velocity and Argo floats that can be used to derive both the intermediate-ocean (1000 m) velocity and the mean dynamic height of the surface relative to 1000 dbar, there now exists the opportunity to directly observe the mean velocity decomposition of the ocean. This study computes the mean Ekman velocity by subtracting the mean referenced velocity derived from Argo data from the mean surface velocity derived from GDP data. This Ekman velocity is slightly stronger than previous observations and shows a spatial structure consistent with a vertical eddy diffusivity that is linearly dependent on wind stress. To do this analysis, the author has to deal with the fact that GDP drifters often lose their drogues, and a product of this research is validation of the wind-slip correction applied to GDP drifters that have lost their drogues.
- Published
- 2016
19. Annual cycles of deep‐ocean biogeochemical export fluxes in subtropical and subantarctic waters, southwest Pacific Ocean
- Author
-
Stephen M. Chiswell, Scott D. Nodder, and Lisa C. Northcote
- Subjects
0106 biological sciences ,Biogeochemical cycle ,010504 meteorology & atmospheric sciences ,010604 marine biology & hydrobiology ,Biogeochemistry ,Subtropics ,Seasonality ,Oceanography ,medicine.disease ,01 natural sciences ,Deep sea ,Pacific ocean ,Geophysics ,Space and Planetary Science ,Geochemistry and Petrology ,Ocean color ,Earth and Planetary Sciences (miscellaneous) ,medicine ,Environmental science ,Particle flux ,0105 earth and related environmental sciences - Published
- 2016
20. The Distribution of Periodical Cicada (Hemiptera: Cicadidae:Magicicada) Brood II in 2013: Disjunct Emergences Suggest Complex Brood Origins
- Author
-
Jin Yoshimura, Stephen M. Chiswell, Chuck Holliday, Richard Grantham, Michael L. Neckermann, Marten J. Edwards, David C. Marshall, Robert L. Sanders, Chris T. Maier, Gerry Bunker, Chris Simon, John R. Cooley, and John D. Zyla
- Subjects
biology ,Extant taxon ,Ecology ,Late 19th century ,Insect Science ,Periodical cicadas ,Zoology ,Disjunct ,biology.organism_classification ,Hemiptera ,Ecology, Evolution, Behavior and Systematics ,Brood - Abstract
The periodical cicadas ( Magicicada spp.) of eastern North America are subdivided into “broods” or locally synchronized populations that share a common emergence schedule. Twelve extant broods have 17-year life cycles and three have 13-year cycles. Most broods contain three morphologically distinct species. In the late 19th century, Charles Marlatt (1898) published a groundbreaking series of maps and emergence schedules accompanied by a sequential numbering scheme designating the 17-year brood that emerged in 1893 “Brood I” (with other potential 17-year broods numbered up to XVII), and the 13-year brood that emerged in 1894 as “Brood XIX” (with potential broods up to XXX). Later editions of Marlatt's work (1907, 1923) added more distributional records. Marlatt's …
- Published
- 2015
21. Tilt‐induced biases in sediment trap functioning
- Author
-
Scott D. Nodder and Stephen M. Chiswell
- Subjects
Geophysics ,Tilt (optics) ,Space and Planetary Science ,Geochemistry and Petrology ,Earth and Planetary Sciences (miscellaneous) ,Sediment trap ,Environmental science ,Biogeochemistry ,Oceanography ,Particle flux ,Geomorphology - Published
- 2015
22. Corrigendum: Off-target capture data, endosymbiont genes and morphology reveal a relict lineage that is sister to all other singing cicadas
- Author
-
Geert Goemans, Chris Simon, Russell C. Meister, Emily Moriarty Lemmon, Katherine Nazario, Piotr Łukasik, Pablo Pessacq, Stephen M. Chiswell, Eric R. L. Gordon, Alan R. Lemmon, M. S. Moulds, Diler Haji, Jeffrey A. Cole, Claudio Veloso, Elizabeth J. Wade, John P. McCutcheon, and Michelle L Kortyna
- Subjects
Lineage (genetic) ,Target capture ,Evolutionary biology ,Morphology (biology) ,Sister ,Biology ,Gene ,Ecology, Evolution, Behavior and Systematics - Published
- 2019
23. Spring blooms and annual cycles of phytoplankton: a unified perspective
- Author
-
Paulo H. R. Calil, Philip W. Boyd, and Stephen M. Chiswell
- Subjects
Oceanography ,Ecology ,Mixed layer ,Phytoplankton ,Temperate climate ,Environmental science ,Stratification (water) ,Upwelling ,Shoaling and schooling ,Aquatic Science ,Spring bloom ,Annual cycle ,Ecology, Evolution, Behavior and Systematics - Abstract
Several hypotheses exist that describe phytoplankton spring blooms in temperate and subpolar oceans: the critical depth, shoaling mixed layer (ML), critical turbulence, onset of stratification and disturbance-recovery hypotheses. These theories appear to be mutually exclusive and none of them describe the annual cycle of phytoplankton biomass. Here, we present a model of the annual cycle in phytoplankton that recognizes that phytoplankton are not always mixed throughout the so-called ML, and that it is important to distinguish between the surface biomass and depth-integrated phytoplankton. Once these important distinctions are made, the annual cycles and blooms in surface and depth-integrated phytoplankton can be described straightforwardly in terms of the physical drivers and biotic responses.
- Published
- 2015
24. Physical oceanography of the deep seas around New Zealand: a review
- Author
-
Helen C Bostock, Michael Williams, Philip Sutton, and Stephen M. Chiswell
- Subjects
Water mass ,Oceanography ,Ecology ,Climatology ,Aquatic Science ,Physical oceanography ,Ecology, Evolution, Behavior and Systematics ,Geology ,Water Science and Technology - Abstract
We review the advances in ‘blue water’ physical oceanography of the seas around New Zealand since the last major review in 1985. By 1985, a basic description had been made of the circulation around...
- Published
- 2015
25. Drifter- and float-derived mean circulation at the surface and 1000 m in the New Zealand region
- Author
-
Stephen M. Chiswell and Philip Sutton
- Subjects
Global Drifter Program ,Float (project management) ,Ecology ,Front (oceanography) ,Aquatic Science ,Geodesy ,Drifter ,Oceanography ,Circulation (fluid dynamics) ,Eddy ,Barotropic fluid ,Ecology, Evolution, Behavior and Systematics ,Argo ,Geology ,Water Science and Technology - Abstract
Global Drifter Program (GDP) drifter data and Argo float data from 2006 to 2013 are used to provide quantitative description and comparison of the mean near-surface (15 m) and 1000 m velocity fields in the New Zealand region. These fields are estimated both from bin-averaging the drifter/float velocities and by fitting non-divergent streamfunctions to the velocities. At both levels, our velocity fields are broadly consistent with previous drifter/float estimates, but provide more detail on the local structure of the mean fields. North of the Subantarctic Front there are large differences between the surface and 1000 m flows, with the Tasman Front being largely absent at 1000 m. South of the Subantarctic Front, where the flow is expected to be more barotropic, there is a closer correspondence between the flows at both levels. Several previously undocumented eddies in the mean flows at both levels are described.
- Published
- 2015
26. Scampi (Metanephrops challengeri) emergence patterns and catchability
- Author
-
Stephen M. Chiswell, I. D. Tuck, Bruce Hartill, and Darren M. Parsons
- Subjects
Metanephrops challengeri ,Geography ,Oceanography ,Ecology ,biology ,Aquatic Science ,Nephrops ,biology.organism_classification ,Burrow ,Ecology, Evolution, Behavior and Systematics ,Metanephrops - Abstract
National Institute of WaterandAtmospheric Research Ltd, Private Bag 14901, Wellington, NewZealand*Corresponding author: tel: +64 93754505; fax: +64 78560151; e-mail: ian.tuck@niwa.co.nzTuck, I. D., Parsons, D. M., Hartill, B. W., and Chiswell, S. M. Scampi (Metanephrops challengeri) emergence patternsand catchability. – ICES Journal of Marine Science, doi: 10.1093/icesjms/fsu244.Received7 August 2014; revised 9December 2014; accepted 10 December 2014.Catchabilityisoftenakeysourceofuncertaintywithanystockassessment,butespeciallyforburrowingspecies,astheiremergentbehaviourisoftenpoorly understood. Quantification of catchability will provide a major step towards improvements in the assessment for many species. Scampi(Metanephrops challengeri) are widely distributed around New Zealand, and as with Nephrops (Norway lobster), they occupy burrows inmuddysubstrate,andareexploitedthroughtrawlfisheries,butareonlyavailabletothesefisherieswhenemergedontheseabed.Burrowemergenceisknowntovaryoverdailyandlongercycles.Uncertaintyovertrawlcatchabilityassociatedwithemergencepatternshasledtothedevelopmentofphotographicsurveyapproachesforscampi,basedonthecountsofburrows.Bothsurveyapproachesrequireanunderstandingofburrowoccu-pancyandemergenceratestoestimatetrawl/photosurveycatchability,whichisakeysourceofuncertainty.WeusedacoustictaggingtoexaminelevelsofandpatternsintheemergenceofMetanephrops,usinghydrophonereceiversmooredclosetotheseabed.Strongemergencecycleswereapparentinrelationtotidalcurrent(higheremergencewithinshorewaterflowacrosstheslope)andtimeofday(peakingjustafterdawn).Thesedatahavesubsequentlybeenusedwithinalength-basedstockassessmentofNewZealandscampi,whichusesemergencedatainconjunctionwithburrow and animal counts from photographic surveys, for the first time, to inform priors for trawl (mean 0.094) and photographic (mean 0.46)surveycatchability, and for burrow occupancy (mean 49.3%).Keywords: acoustic tagging, catchability, emergence, Metanephrops, scampi.
- Published
- 2015
27. Evaluation of Bluelink hindcast BRAN 3.5 at surface and 1000 m
- Author
-
Graham J. Rickard and Stephen M. Chiswell
- Subjects
Global Drifter Program ,Atmospheric Science ,Geotechnical Engineering and Engineering Geology ,Oceanography ,Thermal diffusivity ,Eddy diffusion ,Boundary current ,Drifter ,Climatology ,Computer Science (miscellaneous) ,Ekman transport ,Environmental science ,Hindcast ,Physics::Atmospheric and Oceanic Physics ,Argo - Abstract
We present an evaluation of a 19-year numerical hindcast, Bluelink ReANalysis 3.5 (BRAN 3.5), derived from the Australian Bluelink programme. The evaluation is made for the surface and at 1000 m depth using Global Drifter Program (GDP) drifters and Argo floats, respectively. It is aimed at comparing the model’s ability to correctly simulate the Lagrangian mixing processes. These mixing and dispersal processes are often parameterised in terms of an eddy diffusivity, and we use diffusivity as a metric of comparison. Because the data are spatially sparse and non-uniform in time, the hindcast was sampled at the data locations to provide a model velocity corresponding to each observed velocity. Pseudo-Eulerian mean velocity and eddy kinetic energy fields were computed from bin-averaging of the Lagrangian velocities, and eddy diffusivities were computed from single-particle statistics. The mean field at 2.5 m in BRAN is largely dominated by Ekman transport. The mean velocities at 12.5 m compare well with the GDP drifter mean velocities, except that the Antarctic Circumpolar Current (ACC) is stronger in GDP than in BRAN. At the surface, EKE in BRAN tends to be marginally higher than in GDP. Modelled eddy diffusivity compares well with observed diffusivity, except in the boundary currents and near the equator. At 1000 m, BRAN tends to overestimate the mean field, EKE and eddy diffusivity at low latitudes and underestimate them at higher latitudes.
- Published
- 2014
28. Lagrangian Time Scales and Eddy Diffusivity at 1000 m Compared to the Surface in the South Pacific and Indian Oceans
- Author
-
Stephen M. Chiswell
- Subjects
Surface (mathematics) ,Meteorology ,Scale (ratio) ,Spatial structure ,Eulerian path ,Oceanography ,Geodesy ,Eddy diffusion ,symbols.namesake ,Drifter ,symbols ,Physics::Atmospheric and Oceanic Physics ,Geology ,Argo ,Lagrangian - Abstract
Argo floats cannot be regarded as true Lagrangian drifters because they periodically rise to the surface. Hence, previous estimates of eddy diffusivity at depth using single-particle statistics have been limited to one submerged cycle. However, unless the Lagrangian time scale is significantly shorter than the Argo cycle time, this single-particle calculation can have a large bias. Here, eddy diffusivity computed from single-particle statistics using Argo data is compared to that computed by assuming that Eulerian scales at depth are the same as at the surface, and that the relationship between Lagrangian and Eulerian time scales derived by Middleton is valid. If the methods provide the same answer, one can have confidence in both methods. Eddy diffusivity calculated from the single-particle statistics shows the same spatial structure as that computed from inferred time scale, but is smaller by a factor of about 2. It is suggested that this is because the deep Lagrangian time scale over much of the region is comparable to, or longer than, the 10-day Argo submergence cycle.
- Published
- 2013
29. Non-Gaussian larval dispersal kernels in Gaussian ocean flows
- Author
-
Stephen M. Chiswell
- Subjects
Larva ,Ecology ,Gaussian ,Ocean current ,Aquatic Science ,Biology ,Oceanography ,Atmospheric sciences ,symbols.namesake ,Range (statistics) ,symbols ,Quantitative Biology::Populations and Evolution ,Biological dispersal ,Ecology, Evolution, Behavior and Systematics ,Kernel (category theory) - Abstract
Models of larval dispersal in which ocean currents are Gaussian-distributed provide analytical solutions for the dispersal kernel that are usually assumed to be Gaussian-distributed as well. However, such Gaussian solutions are only valid for a single value of the duration of the larval period. In reality, larvae have a settlement competency period that can range from minutes to >1 yr. Dispersal kernels computed for larvae having a competency period of finite length become non-Gaussian, because later settlers contribute proportionately more to both tails of the kernels than early settlers. In species where the variability in larval duration is large, or mean flows are large compared to the variability, the dispersal kernels approach uniform rather than Gaussian distributions.
- Published
- 2012
30. Annual cycles and spring blooms in phytoplankton: don’t abandon Sverdrup completely
- Author
-
Stephen M. Chiswell
- Subjects
Oceanography ,Ecology ,Mixed layer ,Phytoplankton ,Sverdrup ,Aquatic Science ,Plankton ,Spring bloom ,Annual cycle ,Thermocline ,Algal bloom ,Ecology, Evolution, Behavior and Systematics ,Geology - Abstract
The critical-depth model for the onset of the spring phytoplankton bloom in the North Atlantic has recently been called into question by several researchers. The critical-depth model considers that the spring bloom starts when the mixed layer shoals to become shallower than a critical depth. Satellite and in situ measurements of chlorophyll are used here to show that the critical-depth model is indeed flawed. It is shown that the critical-depth model does not apply in the spring because the basic assumption of an upper layer that is well-mixed in plankton is not met. Instead, the spring bloom forms in shallow near-surface layers that deepen with the onset of thermal stratification. A stratification-onset model for the annual cycle in plankton is proposed that adheres to the conventional idea that the spring bloom represents a change from a deep- mixed regime to a shallow light-driven regime, but where the upper layers are not well mixed in plankton in spring and so the critical-depth model does not apply. Ironically, perhaps, the critical- depth model applies in the autumn and winter when plankton are well-mixed to the seasonal thermocline, so that the critical-depth model can be used to determine whether net winter production is positive or negative.
- Published
- 2011
31. Larval connectivity of harbours via ocean currents: A New Zealand study
- Author
-
Stephen M. Chiswell and Graham J. Rickard
- Subjects
Current (stream) ,Oceanography ,Range (biology) ,Cape ,Ocean current ,Biological dispersal ,Geology ,West coast ,Aquatic Science ,Subtropical front ,Bay - Abstract
Non-indigenous marine species (NIMS) are likely to be introduced into harbours by ballast water discharge or hull fouling, and then spread by natural means in the nearshore/shelf circulation. Reanalysis currents from the Australian Bluelink modelling project are used with particle-tracking to estimate the potential dispersal kernels for major New Zealand ports. A random walk term is added to the particle-tracking algorithm to account for missing variability in the numerical model currents. With few data to validate the model, the choice of added diffusivity is made by comparing simulated dispersal with observed dispersal of Global Program drifters. Histograms of the dispersal times between the ports are computed, along with estimates of the 10 −1 and first percentile dispersal times, which are taken as proxies for the minimum dispersal time between the ports. The 10 −1 percentile times range from 1 day (e.g., Bay of Islands to Whangarei) to several months (Tauranga to Chatham Islands). We identify eight geographical regions, based on the coastal currents and present kernels for a representative port in each region, along with tables of the 10 −1 and first percentile dispersal times for all ports. The regions are: (1) northeast coast of the North Island (influenced by the East Auckland Current), (2) east coast of the North Island (East Cape Current), (3) west coast of the North Island (West Auckland Current/Taranaki Bight circulation), (4) Cook St (circulation in Cook St), (5) east coast of the South Island (Southland Current), (6) west coast of the South Island (Westland Current), (7) Fiordland (Subtropical Front/Southland Current), and (8) the Chatham Islands.
- Published
- 2011
32. Lagrangian and Eulerian estimates of circulation in the lee of Kapiti Island, New Zealand
- Author
-
Stephen M. Chiswell and Craig Stevens
- Subjects
Taranaki Basin ,Geology ,Aquatic Science ,Wake ,Oceanography ,Mooring ,Vortex ,Current (stream) ,Drifter ,Climatology ,Mean flow ,Hydrography - Abstract
Lagrangian drifters, moored acoustic Doppler current meters and hydrographic observations are combined with wind observations to describe the mean and variable nature of flow around Kapiti Island, New Zealand. Thirteen day-long deployments of up to six Lagrangian drifters show the mean flow is to the southwest, with evidence of stronger flows in the channel separating the island from the mainland, and an island wake in the lee of the island. Vortices in this island wake may be tidally driven. Scaling considerations suggest the flow is strong enough that tidal-generated vortices are shed on each tidal cycle. Both the drifters and mooring data suggest that the d’Urville Current around Kapiti Island has a significant wind-driven component. During north-westerlies, the drifters tend to hug the coast, and south-eastwards flows in the Rauoterangi Channel are accelerated. We suggest the observed correlation is the local expression of a South Taranaki basin scale response to the winds.
- Published
- 2010
33. Comment on 'Annual cycles of ecological disturbance and recovery underlying the subarctic Atlantic spring plankton bloom'
- Author
-
Stephen M. Chiswell
- Subjects
Atmospheric Science ,Global and Planetary Change ,geography ,Disturbance (geology) ,geography.geographical_feature_category ,Ecology ,Spring bloom ,Subarctic climate ,Oceanography ,Phytoplankton ,Spring (hydrology) ,Environmental Chemistry ,Environmental science ,Plankton bloom ,General Environmental Science - Published
- 2013
34. Colonisation and connectivity by intertidal limpets among New Zealand, Chatham and Sub-Antarctic Islands. II. Oceanographic connections
- Author
-
Stephen M. Chiswell
- Subjects
Ecology ,Antipodes ,biology ,Lineage (evolution) ,Limpet ,fungi ,Ocean current ,Intertidal zone ,Aquatic Science ,Cellana strigilis ,biology.organism_classification ,Oceanography ,Cellana ,Biological dispersal ,Ecology, Evolution, Behavior and Systematics - Abstract
Satellite-derived measurements of ocean currents made since 1993 were used to examine whether present-day oceanic circulation can explain 2 observed genetic lineages of the intertidal limpet Cellana strigilis in the New Zealand region. The western lineage comprises the South Island of New Zealand, Auckland and Campbell Islands, and the eastern lineage comprises the Chatham, Antipodes and Bounty Islands. Satellite-derived currents were used to simulate potential larval trajectories and hence estimate dispersal times between the islands. A random walk was added to the model to account for missing high-frequency variance in the satellite-derived currents. Surface drifters were used to calibrate the model. Minimum simulated dispersal times between the islands can easily explain the separation of the 2 lineages, but are too long, except between Antipodes and Bounty Islands, to explain the observed homogeneity within the lineages. It is suggested that rare long-distance dispersal events in the ocean, occurring too infrequently to be observed in 15 yr of simulations, influence the gene flow, and the frequency of these events may be estimated by fitting analytical functions to histograms of simulated larval dispersal. For some island pairs that are genetically connected, the maximum 10 d larval duration of C. strigilis appears at the 10–4 percentile. If this genetic connection occurs via larval dispersal, this suggests that connection may occur even when fewer than 1 in 1 million dispersal times is shorter than the larval duration.
- Published
- 2009
35. Sources and sinks of larval settlement in Jasus edwardsii around New Zealand: Where do larvae come from and where do they go?
- Author
-
Stephen M. Chiswell and John D. Booth
- Subjects
Fishery ,Larva ,Ecology ,biology ,Jasus edwardsii ,Aquatic Science ,biology.organism_classification ,Settlement (litigation) ,Ecology, Evolution, Behavior and Systematics ,Phyllosoma - Published
- 2008
36. Altimeter and Current Meter Observations of Internal Tides: Do They Agree?
- Author
-
Stephen M. Chiswell
- Subjects
Ocean surface topography ,Current meter ,Amplitude ,Internal tide ,Flux ,Altimeter ,Internal wave ,Oceanography ,Geodesy ,Mooring ,Geology - Abstract
Baroclinic tides can be observed both remotely from the Ocean Topography Experiment (TOPEX)/Poseidon (T/P) altimeter and in situ using current meters. However, it is rare that current meter moorings have high vertical resolution and are located under T/P ground tracks so that a direct comparison can be made between the two methods of observations. Here, data from a current meter mooring directly under a T/P ground track off the Bounty Plateau, New Zealand, are used to obtain energy estimates of the first baroclinic mode. These estimates are compared with those calculated from the T/P surface elevation. The two methods return estimates of the internal tide that are in agreement in phase and direction but have about a factor-of-2 difference in amplitude (and a factor-of-4 difference in energy); the flux estimates are 787 and 170 W m−1, respectively. Uncertainties in these estimates are relatively large, and there is a low but not negligible probability that the differences are entirely due to measurement error. However, there are other reasons that might explain the differences in the estimates. It may be that the baroclinic tide is highly modulated in time and the current meters were deployed during a period of relatively low amplitude.
- Published
- 2006
37. Distribution of mid‐ and late‐stageJasus edwardsiiphyllosomas: Implications for larval recruitment processes
- Author
-
Stephen M. Chiswell and John D. Booth
- Subjects
East coast ,Larva ,Ecology ,biology ,Jasus edwardsii ,Late stage ,Aquatic Science ,biology.organism_classification ,Phyllosoma ,Oceanography ,Transect ,Ecology, Evolution, Behavior and Systematics ,Water Science and Technology ,Replacement method - Abstract
The relative distributions of mid‐ and late‐stage phyllosomas, and pueruli, of Jasus edwardsii from five research cruises off the east coast of the North Island of New Zealand were analysed. A statistical approach was taken, using a bootstrapping with replacement method to test whether the observed mid‐ and late‐stage phyllosomas could have come from the same distribution. Differences in distribution between mid‐ and late‐stage phyllosomas were very close to significant at 95% confidence for two cruises, significant at 85% confidence for one cruise, and two cruises showed a non‐significant result. When all cruise data were combined into one analysis, the differences between mid‐ and late‐stage phyllosomas were significant with 85% confidence. On average, late‐stage phyllosomas were found 49 km further inshore than mid‐stage phyllosomas. One station during one cruise and one transect during another showed such high abundances that they affected the analyses. When these outlier data were excluded, ...
- Published
- 2005
38. Vertical distribution and diurnal migration patterns ofJasus edwardsiiphyllosomas off the east coast of the North Island, New Zealand
- Author
-
Andrew G. Jeffs, John D. Booth, Barry D. Bruce, Simon Wotherspoon, Russell W. Bradford, and Stephen M. Chiswell
- Subjects
Larva ,Ecology ,biology ,business.industry ,Jasus edwardsii ,Distribution (economics) ,Pelagic zone ,Aquatic Science ,biology.organism_classification ,Panulirus cygnus ,Phyllosoma ,Fishery ,Oceanography ,Biological dispersal ,business ,Diel vertical migration ,Ecology, Evolution, Behavior and Systematics ,Water Science and Technology - Abstract
The rock lobster Jasus edwardsii forms the basis of important fisheries in south‐eastern Australia and New Zealand. Their long pelagic larval phyllosoma phase (12–24 months) raises many questions as to how the larvae are retained and/or recruited into local populations. Recent attempts to model the dispersal of J. edwardsii phyllosoma have had mixed success at reconstructing settlement patterns. However, these models have either ignored vertical distribution or have used that of the western rock lobster, Panulirus cygnus. We report on the vertical distribution and migration of J. edwardsii phyllosomas, collected in March/April 2003 from the Wairarapa Eddy off the east coast of the North Island, New Zealand, and provide a model to describe their vertical distribution. J. edwardsii phyllosoma were primarily recorded within the upper 100 m over similar depth ranges to those reported for other palinurid and scyllarid species. Well‐defined changes in diel vertical distribution were restricted to late‐...
- Published
- 2005
39. Mean and variability in the Wairarapa and Hikurangi Eddies, New Zealand
- Author
-
Stephen M. Chiswell
- Subjects
Dynamic height ,East coast ,Ecology ,Mesoscale meteorology ,Aquatic Science ,Satellite altimeter ,Oceanography ,Eddy ,Anticyclone ,Climatology ,Satellite data ,Altimeter ,Ecology, Evolution, Behavior and Systematics ,Geology ,Water Science and Technology - Abstract
The mean and variability of the circulation off the east coast of the North Island, New Zealand are investigated using shipboard conductivity‐temperature‐depth (CTD) and satellite altimeter data collected between 1993 and 2003. The altimeter data are used to adjust the in situ observations for the mesoscale eddy variability before computing the 11‐year mean in dynamic height. Mean dynamic height shows two anticyclonic eddies, centred near 178.3°E, 41.2°S and 176.2°E, 42.4°S. These locations are consistent with previous historical observations of the Wairarapa and Hikurangi Eddies, respectively. A long‐term trend in both in situ and satellite data shows that dynamic height rose at an average rate of up to 2 dyn cm year‐1 in the centre of the Wairarapa Eddy which is consistent with a strengthening of the eddy over the 11 years. The satellite data show periodic shedding of the Wairarapa Eddy from near East Cape at a rate of between two and three eddies per year. Thus, rather than indicating a perman...
- Published
- 2005
40. Reply to 'Comment on ‘Spring blooms and annual cycles of phytoplankton: a unified perspective’, by Chiswellet al.'
- Author
-
Paulo H. R. Calil, Philip W. Boyd, and Stephen M. Chiswell
- Subjects
0106 biological sciences ,geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Ecology ,010604 marine biology & hydrobiology ,Perspective (graphical) ,Aquatic Science ,01 natural sciences ,Oceanography ,Climatology ,Spring (hydrology) ,Phytoplankton ,Environmental science ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences - Published
- 2016
41. Circulation within the Wairarapa Eddy, New Zealand
- Author
-
Stephen M. Chiswell
- Subjects
East coast ,Ecology ,Flow (psychology) ,Aquatic Science ,Geodesy ,Divergence ,Acoustic Doppler current profiler ,Circulation (fluid dynamics) ,Anticyclone ,Vector field ,Ecology, Evolution, Behavior and Systematics ,Geology ,Geostrophic wind ,Water Science and Technology - Abstract
The Wairarapa Eddy appears as a permanent anticyclonic eddy situated off the east coast of the North Island, New Zealand. In April 2001 a spatial survey of the eddy was made on a ship equipped with an Acoustic Doppler Current Profiler (ADCP). The absolute circulation at 100 m was estimated by objective mapping of the ADCP‐derived velocities to produce a velocity field that has enforced non‐divergence. Assuming that enforcing non‐divergence produces the best estimate of the geostrophic flow, this velocity field can be used as a “level of known motion” to reference geostrophic velocities at other depths. In particular, it can be used to estimate the velocity at 2000 dbar, which is otherwise used in this region as a level of no motion. The resulting flow at 2000 dbar has a mean speed of 0.07 m s‐1, and appears to be well correlated with the surface flow.
- Published
- 2003
42. Trans-Tasman Sea larval transport: Is Australia a source for New Zealand rock lobsters?
- Author
-
Basil R. Stanton, Stephen M. Chiswell, John D. Booth, and John Wilkin
- Subjects
Larva ,Ecology ,biology ,Jasus edwardsii ,fungi ,High mortality ,Aquatic Science ,biology.organism_classification ,Predation ,Gene flow ,Fishery ,Oceanography ,Palinuridae ,Subtropical front ,Sagmariasus ,Ecology, Evolution, Behavior and Systematics - Abstract
Two species of rock lobster (Palinuridae) are commonly found in coastal waters around both New Zealand and Australia. Both species have a relatively long larval phase, which raises the question of how populations can be maintained in regions where the mean flow advects larvae away from the coast. Previous work shows that Jasus edwardsii is genetically indistinguishable between Australia and New Zealand, whereas Sagmariasus verreauxi may be genetically different between the 2 countries. Satellite altimeter data are used here to test the hypothesis that Australia acts as a source of larvae for some New Zealand populations, and to investigate if there is a physical mecha- nism for the apparent lack of gene flow for S. verreauxi. A Lagrangian approach is used in which the western Tasman Sea is seeded with numerical drifters to build up a statistical summary of the likely distribution of larval trajectories. Ignoring biological factors, about 9% of J. edwardsii and about 2% of S. verreauxi larvae might be expected to arrive in New Zealand waters within their respective larval lifetimes. An order-of-magnitude estimate shows that even with extremely high mortality, these rates are high enough for trans-Tasman larval flow to contribute to and possibly maintain some New Zealand populations. Larval flow across the Tasman Sea should be sufficient to maintain trans- Tasman genetic homogeneity in both species. We suggest that 1 reason that S. verreauxi may not be genetically homogenous is that in order to arrive in New Zealand within 1 larval lifetime, they have to cross the Tasman Sea north of the productive Subtropical Front where there is not enough prey to sustain them.
- Published
- 2003
43. Energy Levels, Phase, and Amplitude Modulation of the Baroclinic Tide off Hawaii
- Author
-
Stephen M. Chiswell
- Subjects
Amplitude modulation ,Echo sounding ,Amplitude ,Baroclinity ,Climatology ,Mesoscale meteorology ,Energy flux ,Amplitude distortion ,Oceanography ,Atmospheric sciences ,Phase modulation ,Geology - Abstract
Inverted echo sounder data from Station Aloha north of Oahu, Hawaii, are used to determine the absolute energy levels and time-varying nature of the first-mode baroclinic tide north of Hawaii. The semidiurnal tide amplitude and phase are modulated with 60–120 day periodicity, which indicates interaction between the baroclinic tide and intra-annual mesoscale variability seen off Hawaii. Close to the presumed generation site, there is less phase modulation, and amplitude modulation is uncorrelated with the far-field variability. These results are consistent with a model of phase-locked generation, together with phase and amplitude distortion during propagation. The sense of the amplitude modulation is opposite to that previously observed at decadal timescales. Semidiurnal energy flux at Station Aloha ranges from 2.2 to 8.0 kW m−1, with a mean value of 4.4 kW m−1.
- Published
- 2002
44. Temperature and salinity mean and variability within the subtropical front over the Chatham rise, New Zealand
- Author
-
Stephen M. Chiswell
- Subjects
geography ,geography.geographical_feature_category ,Ecology ,Climatology ,Spring (hydrology) ,Temperature salinity diagrams ,Sampling (statistics) ,Environmental science ,Aquatic Science ,Subtropical front ,Ecology, Evolution, Behavior and Systematics ,Water Science and Technology - Abstract
Estimates are made of the mean and variability in temperature and salinity across the Subtropical Front along 178°30'E, east of New Zealand. These estimates are made from six sections taken over 5 years, but biased towards spring and autumn sampling. Monte‐Carlo simulations of the potential errors introduced by this sampling suggest that the mean fields can be reasonably well determined, but the annual cycles have large relative error. April 1999 residuals were anomalously warm and saline compared with the other five sections. These anomalies may be linked to an increased strength of the Wairarapa Eddy at that time.
- Published
- 2002
45. Wairarapa Coastal Current influence on sea surface temperature in Hawke Bay, New Zealand
- Author
-
Stephen M. Chiswell
- Subjects
Current (stream) ,Sea surface temperature ,East coast ,Oceanography ,Ecology ,Advection ,Upwelling ,Aquatic Science ,Bay ,Ecology, Evolution, Behavior and Systematics ,Geology ,Water Science and Technology - Abstract
The Wairarapa Coastal Current (WCC) flows along the east coast of the North Island, New Zealand. This current has been relatively little studied, and there are few direct measurements of its mean and variability. Here, an indirect method is used to gain some insight into the WCC variability and its effect on coastal temperature. Eight years of coastal temperature from Napier in Hawke Bay are modelled as a bivariate linear expansion of alongshore windstress and solar radiation. In the frequency domain, the modelled temperatures are coherent with observed temperatures, and in the time domain, they are positively correlated for 80% of the time. The model results suggest both that variations in the WCC are wind‐driven, and that alongshore advection accounts for most of the temperature change at Napier. Periods when the modelled temperature is not correlated with observed temperature could be because of episodes of enhanced upwelling, or large‐scale influences breaking down the alongshore temperature ...
- Published
- 2002
46. Determining the internal structure of the ocean off north‐east New Zealand from surface measurements
- Author
-
Stephen M. Chiswell
- Subjects
Surface (mathematics) ,Ecology ,Baroclinity ,Rossby wave ,North east ,Aquatic Science ,Current (stream) ,Circulation (fluid dynamics) ,Climatology ,Bathythermograph ,Ecology, Evolution, Behavior and Systematics ,Sea level ,Geology ,Water Science and Technology - Abstract
The assumption that variability in the circulation around the east coast of the North Island of New Zealand can be described using satellite‐derived sea level and temperature and two empirical modes is tested. Potential errors are quantified if such an assumption is used to derive the internal fields from surface observations. Data from 303 CTD (conductivity‐temperature‐depth) casts made in the region between 1994 and 1999 are first tested against a much larger XBT (expendable bathythermograph) data set to show that they are representative of the expected variability, and then used to compute the empirical modes. The empirical modes are not baroclinic modes, but probably represent the lateral meanderings and variations in strength of the East Auckland Current, together with the presence of Rossby waves in this region. If surface temperature and height can be measured precisely, 60–70% of the variance in the internal temperature and velocity perturbations can be explained with the model. The stand...
- Published
- 2001
47. Influence of along‐shore advection and upwelling on coastal temperature at Kaikoura Peninsula, New Zealand
- Author
-
David R. Schiel and Stephen M. Chiswell
- Subjects
Shore ,geography ,Oceanography ,geography.geographical_feature_category ,Ecology ,Advection ,Peninsula ,Upwelling ,Aquatic Science ,Ecology, Evolution, Behavior and Systematics ,Geology ,Phase relationship ,Water Science and Technology - Abstract
Thermistor data from around Kaikoura Peninsula, New Zealand, show that in the synoptic band, temperature fluctuations at 1 m are coherent with the along-shore wind with a 90° phase differ- ence. At 5 m, however, the coherence is not as high, and the phase relationship is in the opposite sense. Along this coast, wind-driven advection of the coastal current and upwelling have opposite effects on temperature. A simple model is developed which has along-shore advection and upwelling terms parameterised in terms of the wind and two unknown coefficients. Solving for the coefficients shows that at 1 m, temperature variability is determined by along-shore advection, whereas at 5 m, temperature variability is determined principally by upwelling.
- Published
- 2001
48. Occurrence and distribution of Karenia brevisulcata (Dinophyceae) during the 1998 summer toxic outbreaks on the central east coast of New Zealand
- Author
-
Michael J. Uddstrom, F. Hoe Chang, and Stephen M. Chiswell
- Subjects
biology ,Dinoflagellate ,Plant Science ,Aquatic Science ,biology.organism_classification ,Algal bloom ,Fishery ,Cape ,Harbour ,Phytoplankton ,Gymnodinium ,Bloom ,computer ,Dinophyceae ,computer.programming_language - Abstract
Massive mortality of marine life and algal blooms around central New Zealand during January and March 1998 have been attributed to the toxic dinoflagellate, Karenia brevisulcata (= Gymnodinium brevisulcatum). Phytoplankton surveys in January and February 1998 showed the presence of K. brevisulcata both offshore, in the relatively warm, southwards-directed East Auckland and East Cape Currents, and inshore, in the relatively cold, northwards-directed Wairarapa Coastal Current, along the entire east coast of the North Island. Small numbers of this species (200 cells 1−1) were also recorded on the southwest coast of North Island. A bloom of K. brevisulcata occurred in Wellington Harbour during February–March 1998. Reports of human respiratory distress progressed northwards along the Wairarapa Coast at about the same speed (0.23 m s−1) as observed for the Wairarapa Coastal Current, suggesting the passage of a bloom along the coast. We relate the timing of these events to local oceanographic conditions.
- Published
- 2001
49. Eddy energetics in the subtropical front over the Chatham Rise, New Zealand
- Author
-
Stephen M. Chiswell
- Subjects
Momentum (technical analysis) ,Ecology ,Turbulence ,Energetics ,Reynolds stress ,Aquatic Science ,Current (stream) ,Current meter ,Oceanography ,Spatial variability ,Subtropical front ,Ecology, Evolution, Behavior and Systematics ,Geology ,Water Science and Technology - Abstract
The Chatham Rise, which rises to a depth of 400 m immediately to the east of New Zealand, appears to constrain the latitudinal movement of the Subtropical Front (STF). Data from current meters moored over the Chatham Rise are used to estimate the spatial variation of mean and turbulent kinetic energies and Reynolds stresses in and around the STF. Mean currents over 8 months are to the east, and are stronger south of the rise. Mean speeds at 250 m south of the rise are as high as 15 cm s−1 compared to 4.5 cm s−1 north of the rise. In contrast, the eddy kinetic energy is higher to the north at 8.2 J m−3 compared to 3.3 J m−3 to the south. Short‐term current meter moorings over the crest of the rise show no coherence over length scales of 15 km for periods less than 10 days. At 250 m depth, Reynolds stresses are positive north of the rise, and negative south of it, suggesting an export of momentum away from the STF.
- Published
- 2001
50. Coherence of internal tide modulations along the Hawaiian Ridge
- Author
-
Stephen M. Chiswell and Gary T. Mitchum
- Subjects
Dynamic height ,Atmospheric Science ,Pycnocline ,Soil Science ,Aquatic Science ,Oceanography ,Physics::Geophysics ,Geochemistry and Petrology ,Barotropic fluid ,Earth and Planetary Sciences (miscellaneous) ,Physics::Atmospheric and Oceanic Physics ,Sea level ,Earth-Surface Processes ,Water Science and Technology ,geography ,geography.geographical_feature_category ,Ecology ,Internal tide ,Paleontology ,Forestry ,Internal wave ,Geodesy ,Geophysics ,Space and Planetary Science ,Ridge ,Tide gauge ,Astrophysics::Earth and Planetary Astrophysics ,Geology - Abstract
Long time series of sea level from tide gauges along the north side of the Hawaiian Ridge and shorter series of dynamic heights inferred from inverted echo sounders moored just north of the main Hawaiian Islands are examined for evidence of internal tides at the M2 frequency. We find that the amplitudes and phases of the M2 tidal components have low-frequency variability, which is consistent with a superposition of an internal tide with the larger barotropic tide. Further, the low-frequency variability is correlated with low-frequency changes in the depth of the pycnocline, which suggests a simple physical mechanism to account for the low-frequency modulations in the internal tidal amplitude. These modulations are coherent for long distances along the Hawaiian Ridge, indicating a coherent generation of the internal tide that is consistent with acoustic observations in the North Pacific and with recent analyses of sea surface heights from satellite altimetry.
- Published
- 2000
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.