The Southern Antarctic Circumpolar Current Front: physical and biological coupling at South Georgia

Ward, Peter; Whitehouse, M. J.; Meredith, Michael P.; Murphy, Eugene J.; Shreeve, Rachael S.; Korb, Rebecca E.; Watkins, J. L.; Thorpe, Sally; Woodd-Walker, Rachel S.; Brierley, Andrew S.; Cunningham, Nathan; Grant, Sharon; Bone, Doug

doi:10.1016/s0967-0637(02)00119-x

Cited by 47 publications

(35 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This natural iron fertilization mechanism has been suggested to support the large and recurrent phytoplankton blooms observed downstream of South Georgia (Fig. 1, Ward et al, 2002;Borrione and Schlitzer, 2013). The regional differences we report in deep-ocean POC fluxes at P2 and P3 are therefore consistent with the varying levels of chlorophyll a biomass observed around South Georgia resulting from differences in iron supply.…”

Section: Magnitude Of Particle Fluxessupporting

confidence: 85%

“…The waters downstream South Georgia exhibit a large and recurrent phytoplankton bloom (Ward et al, 2002;Borrione and Schlitzer, 2013) characterized by interannual variability in the seasonal pattern (unimodal versus bimodal chlorophyll a peaks, Park et al, 2010;Borrione and Schlitzer, 2013). The bloom is dominated by microplankton diatoms (Korb and Whitehouse, 2004) with a major contribution of Fragilariospsis kerguelensis, Chaetoceros Hyalochaete, Pseudo-nitzschia spp., Eucampia antarctica var.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Strong contribution of diatom resting spores to deep-sea carbon transfer in naturally iron-fertilized waters downstream of South Georgia

Rembauville

Manno

Tarling

et al. 2016

Deep Sea Research Part I: Oceanographic Research Papers

View full text Add to dashboard Cite

a b s t r a c tBiogeochemical and diatom export fluxes are presented from two bathypelagic sediment trap deployments in the Antarctic Zone of the Southern Ocean. One of the sediment traps was deployed in very productive, naturally iron-fertilized waters downstream of South Georgia (P3, 2000 m) and compared to a deployment in moderately productive waters upstream of the island system (P2, 1500 m). At both sites significant diatom export events occurred in spring (November) and contained mostly empty cells that were associated with low particulate organic carbon (POC) fluxes. A summer export pulse occurred one month later at P2 (end February/March) compared to P3 (end January). Diatom fluxes at P3 were one order of magnitude higher than at P2, a difference mainly attributed to the short and intense export of resting spores from Chaetoceros Hyalochaete and Thalassiosira antarctica species. Aside from these resting spores, diatom export assemblages at both sites were dominated by empty Fragilariopsis kerguelensis frustules. The fraction of diatoms exported as empty frustules was considerably lower at P3 (52%) than P2 (91%). This difference was related to the flux of intact diatom resting spores at P3 and may partially explain the lower Si:C export stoichiometry observed at P3 (1.1) compared to P2 (1.5). Through the enumeration of full diatom frustules and subsequent biomass calculations we estimate that diatom resting spores account for 42% of annual POC flux in the productive waters downstream of South Georgia. At both sites the contribution of diatom vegetative stages to POC fluxes was considerably lower (o 5%). From these analyses we conclude that resting spore export contributes towards the slightly higher bathypelagic (POC) flux at P3 (40.6 mmol m À 2 y À 1 ) compared to P2 (26.4 mmol m À 2 y À 1 ). We compared our sediment trap records with previously published diatom assemblage data from the mixed layer and surface sediments (3760 m) around South Georgia. The relative proportion of diatom resting spores within diatom assemblages increases as a function of depth and is explained by selective preservation of their robust frustules. Our study highlights the significance of diatom resting spore export as a carbon vector out of the mixed layer. Furthermore, the contribution or resting spores to POC flux in the bathypelagic ocean and sediments suggests they play a particularly important role in sequestering biologically fixed CO 2 over climatically relevant timescales.

show abstract

Section: Magnitude Of Particle Fluxessupporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Strong contribution of diatom resting spores to deep-sea carbon transfer in naturally iron-fertilized waters downstream of South Georgia

Rembauville

Manno

Tarling

et al. 2016

Deep Sea Research Part I: Oceanographic Research Papers

View full text Add to dashboard Cite

show abstract

“…from acoustic surveys, towed nets, bottle samples) are collected simultaneously (e.g. Ward et al 2002). To overcome these limitations, data from the Argo global array of profiling floats can be used.…”

Section: Introductionmentioning

confidence: 99%

Comparison of gridded sea surface temperature datasets for marine ecosystem studies

Boehme¹,

Lonergan²,

Todd³

2014

Mar. Ecol. Prog. Ser.

View full text Add to dashboard Cite

In assessing impacts of a changing environment on the structure and functioning of marine ecosystems, the challenge remains to distinguish the effects of noise and of temporal and spatial autocorrelation from environmental drivers of biotic change. One analytical approach is to de-trend the data and use the resulting residuals; an alternative method involves use of the raw anomalies and a reduction of the degrees of freedom (df ) to make the hypothesis testing more conservative. Here, we assess the comparability of 3 gridded sea surface temperature (SST) datasets -ERSST V3b, HadISST, and OISST V2 -to in situ measurements. The 1° gridded HadISST and OISST V2 showed the highest similarity, while the weaker correlations with ERSST V3b probably are attributable to its coarser 2°grid. We investigated the performance of 2 commonly applied statistical methods to resolving autocorrelation, and proceeded to correlation analyses between the SST datasets and 2 contemporaneous 15 yr time-series of the somatic growth condition of annual cohorts of Atlantic salmon Salmo salar, which migrate to the Norwegian Sea. For these latter analyses, reducing df could not fully resolve the problem of high positive autocorrelation. The 3 oceanographic datasets do not provide the same correlative outcomes and levels of significance with the salmon time-series. When analysing time-series that pre-date the availability of satellite data, the choice of dataset is restricted to either ERSST V3b or HadISST; but for recent studies (1982 onwards) OISST V2 also is available, and it will be important to assess the relative merits of the 3 SST data sources when interpreting contrasting correlative outcomes.

show abstract

“…Those drifters released in the southwest of the study region travel northeastwards across the Scotia Sea. Of these, the two northernmost deployments (dark blue and jade trajectories) become entrained into the flow of the SACCF and reach the South Georgia shelf in approximately 4 months, while the more southerly drifters follow the mean path of the southern boundary of the ACC (SB) taking Ward et al, 2002) and is about 0:15 m s À1 for the SB . The drifter released to the southwest of the South Georgia shelf (purple line; described in more detail by Thorpe et al, 2002) demonstrates anticyclonic flow around the island with retroflection of the flow to the northeast of South Georgia.…”

Section: Introductionmentioning

confidence: 99%

Tracking passive drifters in a high resolution ocean model: implications for interannual variability of larval krill transport to South Georgia

Thorpe

2004

Deep Sea Research Part I: Oceanographic Research Papers

View full text Add to dashboard Cite

A particle tracking scheme that uses velocity output from an interannually varying forced run of a global ocean circulation model (Parallel Ocean Climate Model; POCM 4C) allows variability in the transport pathways across the Scotia Sea to South Georgia to be examined for the first time. The time-variant surface fluxes introduce realistic variability into the model velocity fields. This causes large variations in near-surface, mixed-layer transport from the Antarctic Peninsula region to South Georgia, an island in the southwest Atlantic sector of the Southern Ocean. The variability occurs on a variety of timescales with seasonal and longer periods of variability apparent in the 18 year time series of results. A quasi-four year period of variability is evident across the region in the sea surface temperature fields of POCM 4C and appears in the particle tracking results. This period, noted in other Southern Ocean data sets and ascribed to the Antarctic Circumpolar Wave, has been observed in the reproductive success of higher marine predators breeding on the island. The predicted oceanographic variability is likely to be significant for the South Georgia ecosystem by affecting the influx into the region of Antarctic krill (Euphausia superba), the main prey of the higher predators. r

show abstract

The Southern Antarctic Circumpolar Current Front: physical and biological coupling at South Georgia

Cited by 47 publications

References 44 publications

Strong contribution of diatom resting spores to deep-sea carbon transfer in naturally iron-fertilized waters downstream of South Georgia

Strong contribution of diatom resting spores to deep-sea carbon transfer in naturally iron-fertilized waters downstream of South Georgia

Comparison of gridded sea surface temperature datasets for marine ecosystem studies

Tracking passive drifters in a high resolution ocean model: implications for interannual variability of larval krill transport to South Georgia

Contact Info

Product

Resources

About