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  • Mixotrophy
  • Southern Ocean
  • 2015-2019  (38)
  • 1960-1964
  • 1945-1949
  • 1
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    Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu
    Publication Date: 2022-10-31
    Description: Dataset: CTD Biogenic Silica
    Description: Biogenic silica concentrations collected from CTD casts during RVIB Nathaniel B. Palmer cruise in the Ross Sea, Southern Ocean from 2017-2018 For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/780191
    Description: NSF Office of Polar Programs (formerly NSF PLR) (NSF OPP) OPP-1644073
    Keywords: Southern Ocean ; Ross Sea ; Biogenic silica
    Repository Name: Woods Hole Open Access Server
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  • 2
    Publication Date: 2022-10-31
    Description: Dataset: NBP1608 TMs: stations
    Description: Dissolved trace metal concentrations from depth profiles during RVIB Nathaniel B. Palmer cruise NBP16-08 in the Southern Ocean from 2016-09-11 to 2016-10-10. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/781773
    Description: NSF Office of Polar Programs (formerly NSF PLR) (NSF OPP) OPP-1443483, NSF Office of Polar Programs (formerly NSF PLR) (NSF OPP) OPP-1443474, NSF Office of Polar Programs (formerly NSF PLR) (NSF OPP) OPP-1443646
    Description: 2020-06-01
    Keywords: Trace metals ; Southern Ocean
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  • 3
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    Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu
    Publication Date: 2022-10-31
    Description: Dataset: Pigments HPLC
    Description: Algal pigment concentrations as measured by HPLC from RVIB Nathaniel B. Palmer cruise in the Ross Sea, Southern Ocean from 2017-2018. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/778881
    Description: NSF Office of Polar Programs (formerly NSF PLR) (NSF OPP) OPP-1644073
    Keywords: Southern Ocean ; Ross Sea ; Phytoplankton pigments ; Chlorophyll
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  • 4
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Newman, L., Heil, P., Trebilco, R., Katsumata, K., Constable, A., van Wijk, E., Assmann, K., Beja, J., Bricher, P., Colemans, R., Costa, D., Diggs, S., Farneti, R., Fawcett, S., Gille, S. T., Hendry, K. R., Henley, S., Hofmann, E., Maksym, T., MazIoff, M., Meijers, A., Meredith, M. M., Moreau, S., Ozsor, B., Robertson, R., Schloss, I., Schofield, O., Shi, J., Sikes, E., Smith, I. J., Swart, S., Wahlin, A., Williams, G., Williams, M. J. M., Herraiz-Borreguero, L., Kern, S., Liesers, J., Massom, R. A., Melbourne-Thomas, J., Miloslavich, P., & Spreen, G. Delivering sustained, coordinated, and integrated observations of the Southern Ocean for global impact. Frontiers in Marine Science, 6, (2019): 433, doi:10.3389/fmars.2019.00433.
    Description: The Southern Ocean is disproportionately important in its effect on the Earth system, impacting climatic, biogeochemical, and ecological systems, which makes recent observed changes to this system cause for global concern. The enhanced understanding and improvements in predictive skill needed for understanding and projecting future states of the Southern Ocean require sustained observations. Over the last decade, the Southern Ocean Observing System (SOOS) has established networks for enhancing regional coordination and research community groups to advance development of observing system capabilities. These networks support delivery of the SOOS 20-year vision, which is to develop a circumpolar system that ensures time series of key variables, and delivers the greatest impact from data to all key end-users. Although the Southern Ocean remains one of the least-observed ocean regions, enhanced international coordination and advances in autonomous platforms have resulted in progress toward sustained observations of this region. Since 2009, the Southern Ocean community has deployed over 5700 observational platforms south of 40°S. Large-scale, multi-year or sustained, multidisciplinary efforts have been supported and are now delivering observations of essential variables at space and time scales that enable assessment of changes being observed in Southern Ocean systems. The improved observational coverage, however, is predominantly for the open ocean, encompasses the summer, consists of primarily physical oceanographic variables, and covers surface to 2000 m. Significant gaps remain in observations of the ice-impacted ocean, the sea ice, depths 〉2000 m, the air-ocean-ice interface, biogeochemical and biological variables, and for seasons other than summer. Addressing these data gaps in a sustained way requires parallel advances in coordination networks, cyberinfrastructure and data management tools, observational platform and sensor technology, two-way platform interrogation and data-transmission technologies, modeling frameworks, intercalibration experiments, and development of internationally agreed sampling standards and requirements of key variables. This paper presents a community statement on the major scientific and observational progress of the last decade, and importantly, an assessment of key priorities for the coming decade, toward achieving the SOOS vision and delivering essential data to all end-users.
    Description: PH was supported by the Australian Government’s Cooperative Research Centers Program through the Antarctica Climate and Ecosystems Cooperative Research Centre, and the International Space Science Institute’s team grant #406. This work contributes to the Australian Antarctica Science projects 4301 and 4390.
    Keywords: Southern Ocean ; observations ; modeling ; ocean–climate interactions ; ecosystem-based management ; long-term monitoring ; international coordination
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  • 5
    Publication Date: 2022-10-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in [citation], doi:[doi]. Swart, S., Gille, S. T., Delille, B., Josey, S., Mazloff, M., Newman, L., Thompson, A. F., Thomson, J., Ward, B., du Plessis, M. D., Kent, E. C., Girton, J., Gregor, L., Heil, P., Hyder, P., Pezzi, L. P., de Souza, R. B., Tamsitt, V., Weller, R. A., & Zappa, C. J. Constraining Southern Ocean air-sea-ice fluxes through enhanced observations. Frontiers in Marine Science, 6, (2019): 421, doi:10.3389/fmars.2019.00421.
    Description: Air-sea and air-sea-ice fluxes in the Southern Ocean play a critical role in global climate through their impact on the overturning circulation and oceanic heat and carbon uptake. The challenging conditions in the Southern Ocean have led to sparse spatial and temporal coverage of observations. This has led to a “knowledge gap” that increases uncertainty in atmosphere and ocean dynamics and boundary-layer thermodynamic processes, impeding improvements in weather and climate models. Improvements will require both process-based research to understand the mechanisms governing air-sea exchange and a significant expansion of the observing system. This will improve flux parameterizations and reduce uncertainty associated with bulk formulae and satellite observations. Improved estimates spanning the full Southern Ocean will need to take advantage of ships, surface moorings, and the growing capabilities of autonomous platforms with robust and miniaturized sensors. A key challenge is to identify observing system sampling requirements. This requires models, Observing System Simulation Experiments (OSSEs), and assessments of the specific spatial-temporal accuracy and resolution required for priority science and assessment of observational uncertainties of the mean state and direct flux measurements. Year-round, high-quality, quasi-continuous in situ flux measurements and observations of extreme events are needed to validate, improve and characterize uncertainties in blended reanalysis products and satellite data as well as to improve parameterizations. Building a robust observing system will require community consensus on observational methodologies, observational priorities, and effective strategies for data management and discovery.
    Description: SS was funded by a Wallenberg Academy Fellowship (WAF 2015.0186). EK was funded by the NERC ORCHESTRA Project (NE/N018095/1). LP was funded by the Advanced Studies in Oceanography of Medium and High Latitudes (CAPES 23038.004304/2014-28) and the Research Productivity Program (CNPq 304009/2016-4). BdS was a research associate at the F.R.S-FNRS. PeH was supported by the Australian Antarctic Science Projects 4301 and 4390, and the Australian Government’s Cooperative Research Centres Programme through the Antarctic Climate and Ecosystems Cooperative Research Centre and the International Space Science Institute Project 406. SG and MM were funded by National Science Foundation awards OCE-1658001 and PLR-1425989. AT was supported by NASA (NNX15AG42G) and NSF (OCE-1756956).
    Keywords: Air-sea/air-sea-ice fluxes ; Southern Ocean ; Ocean-atmosphere interaction ; Climate ; Ocean-ice interaction
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  • 6
    Publication Date: 2022-10-21
    Description: Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 124(7), (2019): 4605-4617, doi: 10.1029/2018JC014928.
    Description: We report the significant impact of near‐inertial waves (NIWs) on vertical mixing and air‐sea carbon dioxide (CO2) fluxes in the Southern Ocean using a biogeochemical model coupled to an eddy‐rich ocean circulation model. The effects of high‐frequency processes are quantified by comparing the fully coupled solution (ONLINE) to two offline simulations based on 5‐day‐averaged output of the ONLINE simulation: one that uses vertical mixing archived from the ONLINE model (CTRL) and another in which vertical mixing is recomputed from the 5‐day average hydrodynamic fields (5dAVG). In this latter simulation, processes with temporal variabilities of a few days including NIWs are excluded in the biogeochemical simulation. Suppression of these processes reduces vertical shear and vertical mixing in the upper ocean, leading to decreased supply of carbon‐rich water from below, less CO2 outgassing in austral winter, and more uptake in summer. The net change amounts up to one third of the seasonal variability in Southern Ocean CO2 flux. Our results clearly demonstrate the importance of resolving high‐frequency processes such as NIWs to better estimate the carbon cycle in numerical model simulations.
    Description: The MITgcm can be obtained from http://mitgcm.org website. Resources supporting this work were provided by the NASA High‐End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center with the Award SMD‐15‐5752. H. S., J. M., and D. J. M. were supported by the NSF MOBY project (OCE‐1048926 and OCE‐1048897). H. S. acknowledges the support by National Research Foundation of Korea (NRF) grant (NRF‐2019R1C1C1003663) and Yonsei University Research Fund of 2018‐22‐0053. D. J. M. also gratefully acknowledges NASA support.
    Description: 2019-12-17
    Keywords: Southern Ocean ; near‐inertial waves ; CO2 ; vertical mixing
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  • 7
    Publication Date: 2018-07-25
    Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Frontiers in Marine Science 5 (2018): 241, doi:10.3389/fmars.2018.00241.
    Description: Cryptophyte algae are globally distributed photosynthetic flagellates found in freshwater, estuarine, and neritic ecosystems. While cryptophytes can be highly abundant and are consumed by a wide variety of protistan predators, few studies have sought to quantify in situ grazing rates on their populations. Here we show that autumnal grazing rates on in situ communities of cryptophyte algae in Chesapeake Bay are high throughout the system, while growth rates, particularly in the lower bay, were low. Analysis of the genetic diversity of cryptophyte populations within dilution experiments suggests that microzooplankton may be selectively grazing the fastest-growing members of the population, which were generally Teleaulax spp. We also demonstrate that potential grazing rates of ciliates and dinoflagellates on fluorescently labeled (FL) Rhodomonas salina, Storeatula major, and Teleaulax amphioxeia can be high (up to 149 prey predator−1 d−1), and that a Gyrodinium sp. and Mesodinium rubrum could be selective grazers. Potential grazing was highest for heterotrophic dinoflagellates, but due to its abundance, M. rubrum also had a high overall impact. This study reveals that cryptophyte algae in Chesapeake Bay can experience extremely high grazing pressure from phagotrophic protists, and that this grazing likely shapes their community diversity.
    Description: The authors thank the National Science Foundation (OCE 1031718 and 1436169) for providing support for this research.
    Keywords: Cryptophytes ; Mixotrophy ; Grazing ; Chesapeake Bay ; Dinoflagellates ; Mesodinium rubrum
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  • 8
    Publication Date: 2022-05-25
    Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Remote Sensing 10 (2018): 331, doi:10.3390/rs10020331.
    Description: The Southern Ocean is the focus of many physical, chemical, and biological analyses due to its global importance and highly variable climate. This analysis of sea surface temperatures (SST) and global teleconnections shows that SSTs are significantly spatially correlated with both the Antarctic Oscillation and the Southern Oscillation, with spatial correlations between the indices and standardized SST anomalies approaching 1.0. Here, we report that the recent positive patterns in the Antarctic and Southern Oscillations are driving negative (cooling) trends in SST in the high latitude Southern Ocean and positive (warming) trends within the Southern Hemisphere sub-tropics and mid-latitudes. The coefficient of regression over the 35-year period analyzed implies that standardized temperatures have warmed at a rate of 0.0142 per year between 1982 and 2016 with a monthly standard error in the regression of 0.0008. Further regression calculations between the indices and SST indicate strong seasonality in response to changes in atmospheric circulation, with the strongest feedback occurring throughout the austral summer and autumn.
    Description: B.S.F. is supported by the NASA/South Carolina Space-grant Graduate Assistantship. A. Macdonald acknowledges support from NOAA Grant #NA160AR4310172.
    Keywords: Southern Ocean ; Sea surface temperature ; Teleconnections ; Antarctic Oscillation ; El Niño-Southern Oscillation ; AVHRR
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  • 9
    Publication Date: 2022-05-25
    Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Frontiers in Marine Science 5 (2018): 13, doi:10.3389/fmars.2018.00013.
    Description: Identifying putative mixotrophic protist species in the environment is important for understanding their behavior, with the recovery of these species in culture essential for determining the triggers of feeding, grazing rates, and overall impact on bacterial standing stocks. In this project, mixotroph abundances determined using tracer ingestion in water and sea ice samples collected in the Ross Sea, Antarctica during the summer of 2011 were compared with data from the spring (Ross Sea) and fall (Arctic) to examine the impacts of bacterivory/mixotrophy. Mixotrophic nanoplankton (MNAN) were usually less abundant than heterotrophs, but consumed more of the bacterial standing stock per day due to relatively higher ingestion rates (1–7 bacteria mixotroph−1 h−1 vs. 0.1–4 bacteria heterotroph−1 h−1). Yet, even with these high rates observed in the Antarctic summer, mixotrophs appeared to have a smaller contribution to bacterivory than in the Antarctic spring. Additionally, putative mixotroph taxa were identified through incubation experiments accomplished with bromodeoxyuridine-labeled bacteria as food, immunoprecipitation (IP) of labeled DNA, and amplification and high throughput sequencing of the eukaryotic ribosomal V9 region. Putative mixotroph OTUs were identified in the IP samples by taxonomic similarity to known phototroph taxa. OTUs that had increased abundance in IP samples compared to the non-IP samples from both surface and chlorophyll maximum (CM) depths were considered to represent active mixotrophy and include ones taxonomically similar to Dictyocha, Gymnodinium, Pentapharsodinium, and Symbiodinium. These OTUs represent target taxa for isolation and laboratory experiments on triggers for mixotrophy, to be combined with qPCR to estimate their abundance, seasonal distribution and potential impact.
    Description: This work was supported by National Science Foundation Grants OPP-0838955 (RG) and OPP-0838847 (RS).
    Keywords: Protist ; Diversity ; Mixotrophy ; Ross Sea ; Amplicon sequencing
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  • 10
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 45 (2018): 5002-5010, doi:10.1029/2017GL076909.
    Description: The Ocean Observatories Initiative air‐sea flux mooring deployed at 54.08°S, 89.67°W, in the southeast Pacific sector of the Southern Ocean, is the farthest south long‐term open ocean flux mooring ever deployed. Mooring observations (February 2015 to August 2017) provide the first in situ quantification of annual net air‐sea heat exchange from one of the prime Subantarctic Mode Water formation regions. Episodic turbulent heat loss events (reaching a daily mean net flux of −294 W/m2) generally occur when northeastward winds bring relatively cold, dry air to the mooring location, leading to large air‐sea temperature and humidity differences. Wintertime heat loss events promote deep mixed layer formation that lead to Subantarctic Mode Water formation. However, these processes have strong interannual variability; a higher frequency of 2 σ and 3 σ turbulent heat loss events in winter 2015 led to deep mixed layers (〉300 m), which were nonexistent in winter 2016.
    Description: NSF Grant Number: PLR-1425989; NSF Grant Number: OCE-1357072; NSF Grant Number: OCE-1658001; UK Natural Environment Research Council; ORCHESTRA Grant Number: NE/N018095/1
    Description: 2018-11-11
    Keywords: Southern Ocean ; Mixed layer ; Subantarctic Mode Water ; Air‐sea heat flux ; Mooring ; Interannual variability
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  • 11
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 45 (2018): 5011-5019, doi:10.1029/2017GL076246.
    Description: The Antarctic Circumpolar Current has highly energetic mesoscale phenomena, but their impacts on phytoplankton biomass, productivity, and biogeochemical cycling are not understood well. We analyze satellite observations and an eddy‐rich ocean model to show that they drive chlorophyll anomalies of opposite sign in winter versus summer. In winter, deeper mixed layers in positive sea surface height (SSH) anomalies reduce light availability, leading to anomalously low chlorophyll concentrations. In summer with abundant light, however, positive SSH anomalies show elevated chlorophyll concentration due to higher iron level, and an iron budget analysis reveals that anomalously strong vertical mixing enhances iron supply to the mixed layer. Features with negative SSH anomalies exhibit the opposite tendencies: higher chlorophyll concentration in winter and lower in summer. Our results suggest that mesoscale modulation of iron supply, light availability, and vertical mixing plays an important role in causing systematic variations in primary productivity over the seasonal cycle.
    Description: 2018-11-17
    Keywords: Mesoscale eddy ; Vertical mixing ; Chlorophyll ; Southern Ocean ; Iron ; Light
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  • 12
    Publication Date: 2022-05-25
    Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Frontiers in Marine Science 5 (2018): 273, doi:10.3389/fmars.2018.00273.
    Description: Mixotrophic flagellates can comprise significant proportions of plankton biomass in marine ecosystems. Despite the growing recognition of the importance of this ecological strategy, and the identification of major environmental factors controlling phagotrophic behavior (light and nutrients), the physiological and molecular mechanisms underlying mixotrophic behavior are still unclear. In this study, we performed RNA-Seq transcriptomic analysis for two mixotrophic prasinophytes, Micromonas polaris and Pyramimonas tychotreta, under dissolved nutrient regimes that altered their ingestion of bacteria prey. Though the strains examined were polar isolates, both belong to genera with widespread distribution. Our aim was to characterize the transcriptomes of these two non-model phytoflagellates, identify transcripts consistent with phagotrophic activity and assess their differential expression in response to nutrient stress. De novo assembly of the transcriptomes yielded large numbers of novel coding transcripts with no known match within public databases. A summary of the transcripts by Gene Ontology terms showed many expected expression patterns, including genes involved in photosynthetic pathways and enzymes implicated in nutrient uptake pathways. Searches of KEGG databases identified several genes associated with intra-cellular digestive pathways actively transcribed in both prasinophytes. Differential expression analysis showed a larger response in P. tychotreta, where 23,373 genes were up-regulated and 1,752 were down-regulated in the low nutrient treatment when phagotrophy was enhanced. In contrast, in M. polaris, low nutrient treatments resulted in up-regulation of 314 transcripts while down-regulating 371. With respect to phagotrophic-related expression, 37 genes were co-expressed in both P. tychotreta and M. polaris, and although the response was less pronounced in M. polaris, it is consistent with differences in observed ingestion behavior. This study presents the first genomic data for Pyramimonas tychotreta, and also contributes to the limited available data for Micromonas polaris. Furthermore, it provides insight into the presence of genes associated with phagocytosis within the Prasinophyceae and contributes to the understanding of potential target genes required for the construction of a complete model of gene regulation of phagocytic behavior in algae.
    Description: The Owlsnest Super-Computing Cluster at Temple University is funded by a National Science Foundation Grant CNS-09-58854. The CUNY HPCC is operated by the College of Staten Island and funded, in part, by grants from the City of New York, State of New York, CUNY Research Foundation, and National Science Foundation Grants CNS-0958379, CNS-0855217, and ACI 1126113. Support for this work was also supplied by National Science Foundation grants PLR-1341362 (RG), PLR-1603538 (RS), and PLR-1603833 (RG).
    Keywords: Mixotrophy ; Pyramimonas ; Micromonas ; RNA-Seq ; Transcriptomics ; Phagotrophy
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  • 13
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 45 (2018): 891–898, doi:10.1002/2017GL076045.
    Description: In this paper we study upwelling pathways and timescales of Circumpolar Deep Water (CDW) in a hierarchy of models using a Lagrangian particle tracking method. Lagrangian timescales of CDW upwelling decrease from 87 years to 31 years to 17 years as the ocean resolution is refined from 1° to 0.25° to 0.1°. We attribute some of the differences in timescale to the strength of the eddy fields, as demonstrated by temporally degrading high-resolution model velocity fields. Consistent with the timescale dependence, we find that an average Lagrangian particle completes 3.2 circumpolar loops in the 1° model in comparison to 0.9 loops in the 0.1° model. These differences suggest that advective timescales and thus interbasin merging of upwelling CDW may be overestimated by coarse-resolution models, potentially affecting the skill of centennial scale climate change projections.
    Description: Department of Energy's RGCM Grant Number: DE-SC0012457; Southern Ocean Carbon and Climate Observation and Modeling Grant Number: PLR-1425989; Climate and Global Change Postdoctoral Fellowship from the National Oceanic and Atmospheric Administration; Australian Research Council DECRA Fellowship Grant Number: DE170100184
    Description: 2018-07-31
    Keywords: Meridional overturning circulation ; Southern Ocean ; Circumpolar Deep Water ; Upwelling ; Eddy parameterization ; Ocean modeling
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  • 14
    Publication Date: 2022-05-25
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Aquatic Microbial Ecology 78 (2017):147-159, doi:10.3354/ame01809.
    Description: The marine ciliate Mesodinium rubrum is known to form large non-toxic red water blooms in estuarine and coastal upwelling regions worldwide. This ciliate relies predominantly upon photosynthesis by using plastids and other organelles it acquires from cryptophyte prey. Although M. rubrum is capable of ingesting different species of cryptophytes, mainly Teleaulax amphioxeia plastids have been detected from wild M. rubrum populations. These observations suggest that either M. rubrum is a selective feeder, or T. amphioxeia are taken up because of higher availability. To test these hypotheses, we determined whether the ciliate showed different grazing rates, growth responses, or plastid retention dynamics when offered Storeatula major, T. amphioxeia, T. acuta, or a mix. When M. rubrum was offered the cryptophyte S. major as prey, no evidence was found for ingestion. In contrast, M. rubrum grazed both Teleaulax spp. equally, was able to easily switch plastid type between them, and the ratio of each in the ciliate reflected the abundance of free-living prey in the culture. M. rubrum grew equally well when acclimated to each plastid type or when having mixed plastids. However, when offered single prey, T. amphioxeia could sustain higher M. rubrum growth rates (μ) over longer periods. Compared to other M. rubrum strains, this culture had higher grazing rates, greater ingestion requirements for reaching μmax, and appeared to rely more on plastid sequestration than de novo division of cryptophyte organelles. Our results suggest that while M. rubrum may prefer Teleaulax-like cryptophytes, they do not select among the species used here.
    Description: This research was supported by Academy of Finland research grant 276268 awarded to E.P. and National Science Foundation research grants IOS 1354773 and OCE 1436169 awarded to M.D.J.
    Keywords: Mixotrophy ; Acquired phototrophy ; Kleptoplastidy ; Grazing ; Prey selection ; Species-specific qPCR ; Mesodinium ; Teleaulax
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  • 15
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2016. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Climate Dynamics 48 (2017): 1297–1307, doi:10.1007/s00382-016-3142-3.
    Description: The turbulent air-sea heat flux feedback (α, in W m-2 K-1) is a major contributor to setting the damping timescale of sea surface temperature (SST) anomalies. In this study we compare the spatial distribution and magnitude of α in the North Atlantic and the Southern Ocean, as estimated from the ERA-Interim reanalysis dataset. The comparison is rationalized in terms of an upper bound on the heat flux feedback, associated with \fast" atmospheric export of temperature and moisture anomalies away from the marine boundary layer, and a lower bound associated with "slow" export. It is found that regions of cold surface waters (≤10°C) are best described as approaching the slow export limit. This conclusion is not only valid at the synoptic scale resolved by the reanalysis data, but also on basin scales. In particular, it applies to the heat flux feedback acting as circumpolar SST anomaly scales are approached in the Southern Ocean, with feedbacks of ≤10 W m-2 K-1. In contrast, the magnitude of the heat flux feed-back is close to that expected from the fast export limit over the Gulf Stream and its recirculation with values on the order of ≈40 W m-2 K-1. Further analysis suggests that this high value reflects a compensation between a moderate thermo-dynamic adjustment of the boundary layer, which tends to weaken the heat flux feedback, and an enhancement of the surface winds over warm SST anomalies, which tend to enhance the feedback.
    Description: Ute Hausmann and John Marshall acknowledge support by the FESD program of NSF.
    Description: 2017-05-04
    Keywords: Sea surface temperature ; Air-sea interaction ; Feedback ; Variability ; Southern Ocean ; North Atlantic
    Repository Name: Woods Hole Open Access Server
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  • 16
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 31 (2017): 922–940, doi:10.1002/2016GB005615.
    Description: A coupled global numerical simulation (conducted with the Community Earth System Model) is used in conjunction with satellite remote sensing observations to examine the role of top-down (grazing pressure) and bottom-up (light, nutrients) controls on marine phytoplankton bloom dynamics in the Southern Ocean. Phytoplankton seasonal phenology is evaluated in the context of the recently proposed “disturbance-recovery” hypothesis relative to more traditional, exclusively “bottom-up” frameworks. All blooms occur when phytoplankton division rates exceed loss rates to permit sustained net population growth; however, the nature of this decoupling period varies regionally in Community Earth System Model. Regional case studies illustrate how unique pathways allow blooms to emerge despite very poor division rates or very strong grazing rates. In the Subantarctic, southeast Pacific small spring blooms initiate early cooccurring with deep mixing and low division rates, consistent with the disturbance-recovery hypothesis. Similar systematics are present in the Subantarctic, southwest Atlantic during the spring but are eclipsed by a subsequent, larger summer bloom that is coincident with shallow mixing and the annual maximum in division rates, consistent with a bottom-up, light limited framework. In the model simulation, increased iron stress prevents a similar summer bloom in the southeast Pacific. In the simulated Antarctic zone (70°S–65°S) seasonal sea ice acts as a dominant phytoplankton-zooplankton decoupling agent, triggering a delayed but substantial bloom as ice recedes. Satellite ocean color remote sensing and ocean physical reanalysis products do not precisely match model-predicted phenology, but observed patterns do indicate regional variability in mechanism across the Atlantic and Pacific.
    Description: NDSEG Graduate Fellowship; National Aeronautics and Space Administration Ocean Biology and Biogeochemistry Program Grant Number: NNX14L86G; NSF Poloar Programs Award Grant Number: 1440435; National Aeronautics and Space Administration Grant Number: NNX14AL86G; NDSEG; National Science Foundation Grant Number: 1440435
    Description: 2017-11-30
    Keywords: Southern Ocean ; Phytoplankton ; Bloom phenology ; Top-down controls ; Bottom-up controls ; Modeling
    Repository Name: Woods Hole Open Access Server
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  • 17
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2017. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 47 (2017): 1291-1305, doi:10.1175/JPO-D-16-0160.1.
    Description: Along-stream variations in the dynamics of the Antarctic Circumpolar Current (ACC) impact heat and tracer transport, regulate interbasin exchange, and influence closure of the overturning circulation. Topography is primarily responsible for generating deviations from zonal-mean properties, mainly through standing meanders associated with regions of high eddy kinetic energy. Here, an idealized channel model is used to explore the spatial distribution of energy exchange and its relationship to eddy geometry, as characterized by both eddy momentum and eddy buoyancy fluxes. Variations in energy exchange properties occur not only between standing meander and quasi-zonal jet regions, but throughout the meander itself. Both barotropic and baroclinic stability properties, as well as the magnitude of energy exchange terms, undergo abrupt changes along the path of the ACC. These transitions are captured by diagnosing eddy fluxes of energy and by adopting the eddy geometry framework. The latter, typically applied to barotropic stability properties, is applied here in the depth–along-stream plane to include information about both barotropic and baroclinic stability properties of the flow. These simulations reveal that eddy momentum fluxes, and thus barotropic instability, play a leading role in the energy budget within a standing meander. This result suggests that baroclinic instability alone cannot capture the dynamics of ACC standing meanders, a challenge for models where eddy fluxes are parameterized.
    Description: The authors all acknowledge support from NSF OCE-1235488. MKY also acknowledges support from the AMS Graduate Student Fellowship.
    Description: 2017-10-12
    Keywords: Southern Ocean ; Channel flows ; Stability ; Topographic effects ; Eddies ; Mesoscale models
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  • 18
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    Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu
    Publication Date: 2022-10-31
    Description: Dataset: McMurdo Sound CTDs
    Description: CTD data were collected as part of an ecosystem study in McMurdo Sound, which is located at the southern extent of the Ross Sea in the Southern Ocean. The major goal of this multi-disciplinary project was to assess the influence of top−down forcing (predation) on pelagic zooplankton and fish. During the first year (3 November 2012 – 21 January 2013), the CTD was deployed through ice core holes in the fast ice (sea ice attached to land), sampling from near surface to depths between 97 and 175 m. Stations were located along a transect in the middle of McMurdo Sound, perpendicular to the fast ice edge. In the second year (17 November 2014 – 1 January 2015), CTD casts were deployed between 100 and 254 m in depth, at stations along the fast ice edge, and along three transects into the fast ice along the eastern side of McMurdo Sound (Ross Island), in the middle of the Sound, and on the western side of the Sound. Chlorophyll fluorescence sensor measurements on the CTD casts were only made during the 2014/2015 field expedition. For a complete list of measurements, refer to the supplemental document 'Field_names.pdf', and a full dataset description is included in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: http://www.bco-dmo.org/dataset/680929
    Description: NSF Division of Polar Programs (NSF PLR) PLR-0944511
    Keywords: Temperature ; Salinity ; PH ; Chlorophyll fluorescence ; Southern Ocean
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  • 19
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    Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu
    Publication Date: 2022-10-31
    Description: Dataset: McMurdo Sound chlorophyll
    Description: Discrete chlorophyll a data were collected as part of an ecosystem study in McMurdo Sound, which is located at the southern extent of the Ross Sea in the Southern Ocean. The major goal of this multi-disciplinary project was to assess the influence of top−down forcing (predation) on pelagic zooplankton and fish. Samples were collected using Niskin water bottles deployed through the fast ice (sea ice attached to land) during two spring/summer seasons: 3 November 2012 – 21 January 2013 and17 November 2014 – 1 January 2015. Water samples were collected at the surface and in the chlorophyll maximum, when present, as determined by a fluorescence sensor during a CTD cast. During 2012/2013, stations were located along a transect in the middle of McMurdo Sound, perpendicular to the fast ice edge. During 2014/2015, stations were located along the fast ice edge, and along three transects into the fast ice along the eastern side of the McMurdo Sound (Ross Island), in the middle of the Sound, and on the western side of the Sound. For a complete list of measurements, refer to the supplemental document 'Field_names.pdf', and a full dataset description is included in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: http://www.bco-dmo.org/dataset/679685
    Description: NSF Division of Polar Programs (NSF PLR) PLR-0944511
    Keywords: Chlorophyll a ; Phytoplankton ; Southern Ocean
    Repository Name: Woods Hole Open Access Server
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  • 20
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 122 (2017): 8208–8224, doi:10.1002/2017JC012985.
    Description: Estimates of the global ocean vertical velocities (Eulerian, eddy-induced, and residual) from a dynamically consistent and data-constrained ocean state estimate are presented and analyzed. Conventional patterns of vertical velocity, Ekman pumping, appear in the upper ocean, with topographic dominance at depth. Intense and vertically coherent upwelling and downwelling occur in the Southern Ocean, which are likely due to the interaction of the Antarctic Circumpolar Current and large-scale topographic features and are generally canceled out in the conventional zonally averaged results. These “elevators” at high latitudes connect the upper to the deep and abyssal oceans and working together with isopycnal mixing are likely a mechanism, in addition to the formation of deep and abyssal waters, for fast responses of the deep and abyssal oceans to the changing climate. Also, Eulerian and parameterized eddy-induced components are of opposite signs in numerous regions around the global ocean, particularly in the ocean interior away from surface and bottom. Nevertheless, residual vertical velocity is primarily determined by the Eulerian component, and related to winds and large-scale topographic features. The current estimates of vertical velocities can serve as a useful reference for investigating the vertical exchange of ocean properties and tracers, and its complex spatial structure ultimately permits regional tests of basic oceanographic concepts such as Sverdrup balance and coastal upwelling/downwelling.
    Description: National Science Foundation Grant Numbers: OCE-1736633 , OCE-1534618 , OCE-0961713; National Oceanic and Atmospheric Administration Grant Number: NA10OAR4310135
    Description: 2018-04-27
    Keywords: Vertical velocity ; Vertical transport ; Vertical exchange ; Ocean state estimate ; Climate change ; Southern Ocean
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  • 21
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 122 (2017): 2960–2975, doi:10.1002/2016JC012494.
    Description: Traditionally, the mechanism driving the seasonal restratification of the Southern Ocean mixed layer (ML) is thought to be the onset of springtime warming. Recent developments in numerical modeling and North Atlantic observations have shown that submesoscale ML eddies (MLE) can drive a restratifying flux to shoal the deep winter ML prior to solar heating at high latitudes. The impact of submesoscale processes on the intraseasonal variability of the Subantarctic ML is still relatively unknown. We compare 5 months of glider data in the Subantarctic Zone to simulations of a 1-D mixing model to show that the magnitude of restratification of the ML cannot be explained by heat, freshwater, and momentum fluxes alone. During early spring, we estimate that periodic increases in the vertical buoyancy flux by MLEs caused small increases in stratification, despite predominantly down-front winds that promote the destruction of stratification. The timing of seasonal restratification was consistent between 1-D model estimates and the observations. However, during up-front winds, the strength of springtime stratification increased over twofold compared to the 1-D model, with a rapid shoaling of the MLD from 〉200 m to 〈100 m within a few days. The ML stratification is further modified under a negative Ekman buoyancy flux during down-front winds, resulting in the destruction of ML stratification and deepening of the MLD. These results propose the importance of submesoscale buoyancy fluxes enhancing seasonal restratification and mixing of the Subantarctic ML.
    Description: South African NRF-SANAP Grant Number: SNA14071475720; NSF Grant Number: OCE-I434788
    Description: 2017-10-08
    Keywords: Ocean gliders ; Southern Ocean ; Seasonal stratification ; 1-D mixed-layer model ; Mixed layer eddies ; Ekman buoyancy flux
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  • 22
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 121 (2016): 6635–6649, doi:10.1002/2016JC011714.
    Description: We investigate the role of mesoscale eddies in modulating air-sea CO2 flux and associated biogeochemical fields in Drake Passage using in situ observations and an eddy-resolving numerical model. Both observations and model show a negative correlation between temperature and partial pressure of CO2 (pCO2) anomalies at the sea surface in austral summer, indicating that warm/cold anticyclonic/cyclonic eddies take up more/less CO2. In austral winter, in contrast, relationships are reversed: warm/cold anticyclonic/cyclonic eddies are characterized by a positive/negative pCO2 anomaly and more/less CO2 outgassing. It is argued that DIC-driven effects on pCO2 are greater than temperature effects in austral summer, leading to a negative correlation. In austral winter, however, the reverse is true. An eddy-centric analysis of the model solution reveals that nitrate and iron respond differently to the same vertical mixing: vertical mixing has a greater impact on iron because its normalized vertical gradient at the base of the surface mixed layer is an order of magnitude greater than that of nitrate.
    Description: NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center Grant Number: SMD-15-5752; NSF MOBY project Grant Numbers: (OCE-1048926), OCE-1259388, PLR-1341647, AOAS-0944761, and AOAS-066975; NOAA Climate Program Office Grant Number: (NA12OAR4310058)
    Description: 2017-03-10
    Keywords: CO2 flux ; Mesoscale eddy ; Southern Ocean ; Vertical mixing ; Nutrient fluxes
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  • 23
    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Endangered Species Research 30 (2016): 239-253, doi:10.3354/esr00739.
    Description: Distribution and movement patterns of Antarctic blue whales Balaenoptera musculus intermedia at large temporal and spatial scales are still poorly understood. The objective of this study was to explore spatio-temporal distribution patterns of Antarctic blue whales in the Atlantic sector of the Southern Ocean, using passive acoustic monitoring data. Multi-year data were collected between 2008 and 2013 by 11 recorders deployed in the Weddell Sea and along the Greenwich meridian. Antarctic blue whale Z-calls were detected via spectrogram cross-correlation. A Blue Whale Index was developed to quantify the proportion of time during which acoustic energy from Antarctic blue whales dominated over background noise. Our results show that Antarctic blue whales were acoustically present year-round, with most call detections between January and April. During austral summer, the number of detected calls peaked synchronously throughout the study area in most years, and hence, no directed meridional movement pattern was detectable. During austral winter, vocalizations were recorded at latitudes as high as 69°S, with sea ice cover exceeding 90%, suggesting that some Antarctic blue whales overwinter in Antarctic waters. Polynyas likely serve as an important habitat for baleen whales during austral winter, providing food and reliable access to open water for breathing. Overall, our results support increasing evidence of a complex and non-obligatory migratory behavior of Antarctic blue whales, potentially involving temporally and spatially dynamic migration routes and destinations, as well as variable timing of migration to and from the feeding grounds.
    Keywords: Passive acoustic monitoring ; Antarctic blue whale ; Balaenoptera musculus intermedia ; Baleen whale migration ; Southern Ocean
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  • 24
    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Global Biogeochemical Cycles 30 (2016): 1124–1144, doi:10.1002/2016GB005414.
    Description: The Great Calcite Belt (GCB) is a region of elevated surface reflectance in the Southern Ocean (SO) covering ~16% of the global ocean and is thought to result from elevated, seasonal concentrations of coccolithophores. Here we describe field observations and experiments from two cruises that crossed the GCB in the Atlantic and Indian sectors of the SO. We confirm the presence of coccolithophores, their coccoliths, and associated optical scattering, located primarily in the region of the subtropical, Agulhas, and Subantarctic frontal regions. Coccolithophore-rich regions were typically associated with high-velocity frontal regions with higher seawater partial pressures of CO2 (pCO2) than the atmosphere, sufficient to reverse the direction of gas exchange to a CO2 source. There was no calcium carbonate (CaCO3) enhancement of particulate organic carbon (POC) export, but there were increased POC transfer efficiencies in high-flux particulate inorganic carbon regions. Contemporaneous observations are synthesized with results of trace-metal incubation experiments, 234Th-based flux estimates, and remotely sensed observations to generate a mandala that summarizes our understanding about the factors that regulate the location of the GCB.
    Description: National Science Foundation Grant Numbers: OCE-0961660, OCE-0728582, OCE-0961414, OCE-0960880; National Aeronautical and Space Administration Grant Numbers: NNX11AO72G, NNX11AL93G, NNX14AQ41G, NNX14AQ43A, NNX14AL92G, NNX14AM77G
    Keywords: Coccolithophores ; Trace metals ; Carbonate chemistry ; Southern Ocean ; Subantarctic Front ; Subtropical Front
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  • 25
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2016. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 46 (2016): 1309-1321, doi:10.1175/JPO-D-15-0068.1.
    Description: Direct measurements of oceanic turbulent parameters were taken upstream of and across Drake Passage, in the region of the Subantarctic and Polar Fronts. Values of turbulent kinetic energy dissipation rate ε estimated by microstructure are up to two orders of magnitude lower than previously published estimates in the upper 1000 m. Turbulence levels in Drake Passage are systematically higher than values upstream, regardless of season. The dissipation of thermal variance χ is enhanced at middepth throughout the surveys, with the highest values found in northern Drake Passage, where water mass variability is the most pronounced. Using the density ratio, evidence for double-diffusive instability is presented. Subject to double-diffusive physics, the estimates of diffusivity using the Osborn–Cox method are larger than ensemble statistics based on ε and the buoyancy frequency.
    Description: This work was supported by grants from the U.S. National Science Foundation.
    Description: 2016-10-05
    Keywords: Geographic location/entity ; Southern Ocean ; Circulation/ Dynamics ; Diapycnal mixing ; Mixing ; Turbulence ; Atm/Ocean Structure/ Phenomena ; Fronts ; Observational techniques and algorithms ; Profilers, oceanic
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  • 26
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    Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu
    Publication Date: 2022-10-31
    Description: Dataset: CTD_MOCNESS1
    Description: CTD data from MOCNESS-1m tows in the Southern Ocean around the South Shetland Islands and Palmer Archipelago, Western Antarctic Peninsula in November 2011. For a complete list of measurements, refer to the supplemental document 'Field_names.pdf', and a full dataset description is included in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: http://www.bco-dmo.org/dataset/488871
    Description: NSF Antarctic Sciences (NSF ANT) ANT-1044982
    Keywords: Southern Ocean ; CTD ; MOCNESS ; Zooplankton
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  • 27
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    Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu
    Publication Date: 2022-10-31
    Description: Dataset: CTD data from LMG1110
    Description: Hydrographic data from 20 CTD casts in the Southern Ocean around the South Shetland Islands and Palmer Archipelago, Western Antarctic Peninsula in November 2011. For a complete list of measurements, refer to the supplemental document 'Field_names.pdf', and a full dataset description is included in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: http://www.bco-dmo.org/dataset/559174
    Description: NSF Antarctic Sciences (NSF ANT) ANT-1044982
    Keywords: CTD ; Temperature ; Conductivity ; Depth ; Southern Ocean
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  • 28
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    Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu
    Publication Date: 2022-10-31
    Description: Dataset: alongtrack
    Description: This alongtrack data set consists of a single file produced for each day of the LMG1110 cruise, from 11/2/2011 to 12/1/2011. The LMG alongtrack data acquisition systems continuously log data from a suite of instruments throughout the cruise. Data were obtained primarily by applying calibrations to raw data and decimating to whole point intervals. However, several fields are derived measurements from more than a single raw input. For a complete list of measurements, refer to the supplemental document 'Field_names.pdf', and a full dataset description is included in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: http://www.bco-dmo.org/dataset/3636
    Description: NSF Antarctic Sciences (NSF ANT) ANT-1044982
    Keywords: Southern Ocean ; Event log
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  • 29
    Publication Date: 2022-05-26
    Description: Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in Ecology Letters 19 (2016): 393-402, doi:10.1111/ele.12572.
    Description: In marine ecosystems, acquired phototrophs|organisms that obtain their photo- synthetic ability by hosting endosymbionts or stealing plastids from their prey|are omnipresent. Such taxa function as intraguild predators yet depend on their prey to periodically obtain chloroplasts. We present new theory for the effects of acquired phototrophy on community dynamics by analyzing a mathematical model of this predator-prey interaction and experimentally verifying its predictions with a lab- oratory model system. We show that acquired phototrophy stabilizes coexistence, but that the nature of this coexistence exhibits a `paradox of enrichment:' as light increases, the coexistence between the acquired phototroph and its prey transitions from a stable equilibrium to boom-bust cycles whose amplitude increases with light availability. In contrast, heterotrophs and mixotrophic acquired phototrophs (that obtain 〈30% of their carbon from photosynthesis) do not exhibit such cycles. This prediction matches eld observations, in which only strict (〉95% of carbon from photosynthesis) acquired phototrophs form blooms.
    Description: HVM is supported by a United States National Science Foundation Postdoctoral Research Fellowship in Biology (Grant No. DBI-1401332). EP is supported by the Academy of Finland through research grant 276268. MDJ acknowledges NSF Grant No. IOS-1354773. MGN acknowledges support provided by the Independent Research and Development Program at the Woods Hole Oceanographic Institution.
    Description: 2017-02-01
    Keywords: Acquired metabolic potential ; Community ecology ; Intraguild predation ; Kleptoplastidy ; Mesodinium rubrum ; Mixotrophy
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 30
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2015. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 46 (2016): 417-437, doi:10.1175/JPO-D-15-0055.1.
    Description: In the stratified ocean, turbulent mixing is primarily attributed to the breaking of internal waves. As such, internal waves provide a link between large-scale forcing and small-scale mixing. The internal wave field north of the Kerguelen Plateau is characterized using 914 high-resolution hydrographic profiles from novel Electromagnetic Autonomous Profiling Explorer (EM-APEX) floats. Altogether, 46 coherent features are identified in the EM-APEX velocity profiles and interpreted in terms of internal wave kinematics. The large number of internal waves analyzed provides a quantitative framework for characterizing spatial variations in the internal wave field and for resolving generation versus propagation dynamics. Internal waves observed near the Kerguelen Plateau have a mean vertical wavelength of 200 m, a mean horizontal wavelength of 15 km, a mean period of 16 h, and a mean horizontal group velocity of 3 cm s−1. The internal wave characteristics are dependent on regional dynamics, suggesting that different generation mechanisms of internal waves dominate in different dynamical zones. The wave fields in the Subantarctic/Subtropical Front and the Polar Front Zone are influenced by the local small-scale topography and flow strength. The eddy-wave field is influenced by the large-scale flow structure, while the internal wave field in the Subantarctic Zone is controlled by atmospheric forcing. More importantly, the local generation of internal waves not only drives large-scale dissipation in the frontal region but also downstream from the plateau. Some internal waves in the frontal region are advected away from the plateau, contributing to mixing and stratification budgets elsewhere.
    Description: A.M. was supported by the joint CSIRO-University of Tasmania Quantitative Marine Science (QMS) program and the 2009 CSIRO Wealth from Ocean Flagship Collaborative Fund. K.L.P.’s salary support was provided by Woods Hole Oceanographic Institution bridge support funds. B.M.S. was supported by the Australian Climate Change Science Program.
    Description: 2016-06-07
    Keywords: Geographic location/entity ; Southern Ocean ; Circulation/ Dynamics ; Internal waves ; Mixing ; Wave properties ; Observational techniques and algorithms ; In situ oceanic observations ; Profilers, oceanic
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  • 31
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    Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu
    Publication Date: 2022-05-26
    Description: Dataset: event log LMG11-10
    Description: The event log to record all instrument deployments during the cruise. For a complete list of measurements, refer to the supplemental document 'Field_names.pdf', and a full dataset description is included in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: http://www.bco-dmo.org/dataset/3565
    Description: NSF Antarctic Sciences (NSF ANT) ANT-1044982
    Keywords: Southern Ocean
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  • 32
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2015. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 45 (2015): 966–987, doi:10.1175/JPO-D-14-0110.1.
    Description: A key remaining challenge in oceanography is the understanding and parameterization of small-scale mixing. Evidence suggests that topographic features play a significant role in enhancing mixing in the Southern Ocean. This study uses 914 high-resolution hydrographic profiles from novel EM-APEX profiling floats to investigate turbulent mixing north of the Kerguelen Plateau, a major topographic feature in the Southern Ocean. A shear–strain finescale parameterization is applied to estimate diapycnal diffusivity in the upper 1600 m of the ocean. The indirect estimates of mixing match direct microstructure profiler observations made simultaneously. It is found that mixing intensities have strong spatial and temporal variability, ranging from O(10−6) to O(10−3) m2 s−1. This study identifies topographic roughness, current speed, and wind speed as the main factors controlling mixing intensity. Additionally, the authors find strong regional variability in mixing dynamics and enhanced mixing in the Antarctic Circumpolar Current frontal region. This enhanced mixing is attributed to dissipating internal waves generated by the interaction of the Antarctic Circumpolar Current and the topography of the Kerguelen Plateau. Extending the mixing observations from the Kerguelen region to the entire Southern Ocean, this study infers a large water mass transformation rate of 17 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1) across the boundary of Antarctic Intermediate Water and Upper Circumpolar Deep Water in the Antarctic Circumpolar Current. This work suggests that the contribution of mixing to the Southern Ocean overturning circulation budget is particularly significant in fronts.
    Description: AM was supported by the joint CSIRO–University of Tasmania Quantitative Marine Science (QMS) program and the 2009 CSIRO Wealth from Ocean Flagship Collaborative Fund. BMS was supported by the Australian Climate Change Science Program, jointly funded by the Department of the Environment and CSIRO. KLPs salary support was provided by Woods Hole Oceanographic Institution bridge support funds.
    Description: 2015-10-01
    Keywords: Geographic location/entity ; Southern Ocean ; Circulation/ Dynamics ; Diapycnal mixing ; Fronts ; Ocean circulation ; Topographic effects ; Atm/Ocean Structure/ Phenomena ; Mixing
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  • 33
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2015. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 45 (2015): 1610–1631, doi:10.1175/JPO-D-14-0047.1.
    Description: The use of a measure to diagnose submesoscale isopycnal diffusivity by determining the best match between observations of a tracer and simulations with varying small-scale diffusivities is tested. Specifically, the robustness of a “roughness” measure to discriminate between tracer fields experiencing different submesoscale isopycnal diffusivities and advected by scaled altimetric velocity fields is investigated. This measure is used to compare numerical simulations of the tracer released at a depth of about 1.5 km in the Pacific sector of the Southern Ocean during the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) field campaign with observations of the tracer taken on DIMES cruises. The authors find that simulations with an isopycnal diffusivity of ~20 m2 s−1 best match observations in the Pacific sector of the Antarctic Circumpolar Current (ACC), rising to ~20–50 m2 s−1 through Drake Passage, representing submesoscale processes and any mesoscale processes unresolved by the advecting altimetry fields. The roughness measure is demonstrated to be a statistically robust way to estimate a small-scale diffusivity when measurements are relatively sparse in space and time, although it does not work if there are too few measurements overall. The planning of tracer measurements during a cruise in order to maximize the robustness of the roughness measure is also considered. It is found that the robustness is increased if the spatial resolution of tracer measurements is increased with the time since tracer release.
    Description: We thank the U.K. Natural Environment Research Council and the U.S. National Science Foundation for funding the DIMES project.
    Description: 2015-12-01
    Keywords: Geographic location/entity ; Southern Ocean ; Circulation/ Dynamics ; Diffusion ; Physical Meteorology and Climatology ; Isopycnal mixing ; Observational techniques and algorithms ; Tracers ; Models and modeling ; Model comparison ; Tracers
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  • 34
    Publication Date: 2022-05-25
    Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in BMC Genomics 16 (2015): 805, doi:10.1186/s12864-015-2052-9.
    Description: Organelle retention is a form of mixotrophy that allows organisms to reap metabolic benefits similar to those of photoautotrophs through capture of algal prey and sequestration of their plastids. Mesodinium rubrum is an abundant and broadly distributed photosynthetic marine ciliate that steals organelles from cryptophyte algae, such as Geminigera cryophila. M. rubrum is unique from most other acquired phototrophs because it also steals a functional nucleus that facilitates genetic control of sequestered plastids and other organelles. We analyzed changes in G. cryophila nuclear gene expression and transcript abundance after its incorporation into the cellular architecture of M. rubrum as an initial step towards understanding this complex system. We compared Illumina-generated transcriptomes of the cryptophyte Geminigera cryophila as a free-living cell and as a sequestered nucleus in M. rubrum to identify changes in protein abundance and gene expression. After KEGG annotation, proteins were clustered by functional categories, which were evaluated for over- or under-representation in the sequestered nucleus. Similarly, coding sequences were grouped by KEGG categories/pathways, which were then evaluated for over- or under-expression via read count strategies. At the time of sampling, the global transcriptome of M. rubrum was dominated (~58–62 %) by transcription from its stolen nucleus. A comparison of transcriptomes from free-living G. cryophila cells to those of the sequestered nucleus revealed a decrease in gene expression and transcript abundance for most functional protein categories within the ciliate. However, genes coding for proteins involved in photosynthesis, oxidative stress reduction, and several other metabolic pathways revealed striking exceptions to this general decline. Major changes in G. cryophila transcript expression after sequestration by M. rubrum and the ciliate’s success as a photoautotroph imply some level of control or gene regulation by the ciliate and at the very least reflect a degree of coordination between host and foreign organelles. Intriguingly, cryptophyte genes involved in protein transport are significantly under-expressed in M. rubrum, implicating a role for the ciliate’s endomembrane system in targeting cryptophyte proteins to plastid complexes. Collectively, this initial portrait of an acquired transcriptome within a dynamic and ecologically successful ciliate highlights the remarkable cellular and metabolic chimerism of this system.
    Description: The authors wish to acknowledge the support of NSF award 1354773.
    Keywords: Mesodinium rubrum ; Geminigera cryophila ; Karyoklepty ; Acquired phototrophy ; Transcriptome ; Differential gene expression ; Chimeric metabolism ; Organelle retention ; Mixotrophy
    Repository Name: Woods Hole Open Access Server
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  • 35
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 120 (2015): 1065–1078, doi:10.1002/2014JC010292.
    Description: The role of mesoscale eddies in the uptake of anthropogenic chlorofluorocarbon-11 (CFC-11) gas is investigated with a 1/20° eddy-resolving numerical ocean model of a region of the Southern Ocean. With a relatively fast air-sea equilibrium time scale (about a month), the air-sea CFC-11 flux quickly responds to the changes in the mixed layer CFC-11 partial pressure (pCFC-11). At the mesoscale, significant correlations are observed between pCFC-11 anomaly, anomalies in sea surface temperature (SST), net heat flux, and mixed layer depth. An eddy-centric analysis of the simulated CFC-11 field suggests that anticyclonic warm-core eddies generate negative pCFC-11 anomalies and cyclonic cold-core eddies generate positive anomalies of pCFC-11. Surface pCFC-11 is modulated by mixed layer dynamics in addition to CFC-11 air-sea fluxes. A negative cross correlation between mixed layer depth and surface pCFC-11 anomalies is linked to higher CFC-11 uptake in anticyclones and lower CFC-11 uptake in cyclones, especially in winter. An almost exact asymmetry in the air-sea CFC-11 flux between cyclones and anticyclones is found.
    Description: We gratefully acknowledge NSF support of the MOBY project (grant OCE-1048926 to MIT and OCE-1048897 to WHOI). In addition, P.G. and D.J.M. thank NASA for partial support of this work through grant NNX13AE47G.
    Description: 2015-08-23
    Keywords: Mesoscale eddies ; Chlorofluorocarbon-11 ; Air-sea flux ; Southern Ocean
    Repository Name: Woods Hole Open Access Server
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  • 36
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 42 (2015): 3450–3457, doi:10.1002/2015GL063216.
    Description: The impact of a mesoscale eddy on the magnitude and spatial distribution of diapycnal ocean mixing is investigated using a set of hydrographic and microstructure measurements collected in the Southern Ocean. These data sampled a baroclinic, middepth eddy formed during the disintegration of a deep boundary current. Turbulent dissipation is suppressed within the eddy but is elevated by up to an order of magnitude along the upper and lower eddy boundaries. A ray tracing approximation is employed as a heuristic device to elucidate how the internal wave field evolves in the ambient velocity and stratification conditions accompanying the eddy. These calculations are consistent with the observations, suggesting reflection of internal wave energy from the eddy center and enhanced breaking through critical layer processes along the eddy boundaries. These results have important implications for understanding where and how internal wave energy is dissipated in the presence of energetic deep geostrophic flows.
    Description: Natural Environment Research Council (NERC). Grant Numbers: NE/E007058/1, NE/E005667/1; U.S. National Science Foundation. Grant Numbers: OCE-1231803, OCE-0927583, OCE-1030309; NERC
    Description: 2015-11-07
    Keywords: Mixing ; Eddy ; Turbulent dissipation ; Internal waves ; Southern Ocean ; Ray tracing
    Repository Name: Woods Hole Open Access Server
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  • 37
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Atmospheres 120 (2015): 1794–1807, doi:10.1002/2014JD022483.
    Description: Satellite observations of carbon dioxide (CO2) offer novel and distinctive opportunities for improving our quantitative understanding of the carbon cycle. Prospective observations include those from space-based lidar such as the active sensing of CO2 emissions over nights, days, and seasons (ASCENDS) mission. Here we explore the ability of such a mission to detect regional changes in CO2 fluxes. We investigate these using three prototypical case studies, namely, the thawing of permafrost in the northern high latitudes, the shifting of fossil fuel emissions from Europe to China, and changes in the source/sink characteristics of the Southern Ocean. These three scenarios were used to design signal detection studies to investigate the ability to detect the unfolding of these scenarios compared to a baseline scenario. Results indicate that the ASCENDS mission could detect the types of signals investigated in this study, with the caveat that the study is based on some simplifying assumptions. The permafrost thawing flux perturbation is readily detectable at a high level of significance. The fossil fuel emission detectability is directly related to the strength of the signal and the level of measurement noise. For a nominal (lower) fossil fuel emission signal, only the idealized noise-free instrument test case produces a clearly detectable signal, while experiments with more realistic noise levels capture the signal only in the higher (exaggerated) signal case. For the Southern Ocean scenario, differences due to the natural variability in the El Niño–Southern Oscillation climatic mode are primarily detectable as a zonal increase.
    Description: This material is based upon work supported by the National Aeronautics and Space Administration under grant NNX08AJ92G issued through the Research Opportunities in Space and Earth Sciences Carbon Cycle Science program and by Jet Propulsion Laboratory subcontract 1442785 as well as the ASCENDS Science Requirements Definition Team. S. Doney acknowledges support from U.S. National Science Foundation (AGS-1048827). K. Schaefer acknowledges support from the National Oceanic and Atmospheric Administration under grant NA09OAR4310063 and from the National Aeronautics and Space Administration under grant NNX10AR63G.
    Description: 2015-09-11
    Keywords: CO2 fluxes ; Space-based lidar ; Southern Ocean ; Signal detection ; Permafrost thawing ; Fossil fuel emissions
    Repository Name: Woods Hole Open Access Server
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  • 38
    Publication Date: 2022-05-26
    Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Frontiers in Microbiology 6 (2015): 1090, doi:10.3389/fmicb.2015.01090.
    Description: Antarctica polynyas support intense phytoplankton blooms, impacting their environment by a substantial depletion of inorganic carbon and nutrients. These blooms are dominated by the colony-forming haptophyte Phaeocystis antarctica and they are accompanied by a distinct bacterial population. Yet, the ecological role these bacteria may play in P. antarctica blooms awaits elucidation of their functional gene pool and of the geochemical activities they support. Here, we report on a metagenome (~160 million reads) analysis of the microbial community associated with a P. antarctica bloom event in the Amundsen Sea polynya (West Antarctica). Genomes of the most abundant Bacteroidetes and Proteobacteria populations have been reconstructed and a network analysis indicates a strong functional partitioning of these bacterial taxa. Three of them (SAR92, and members of the Oceanospirillaceae and Cryomorphaceae) are found in close association with P. antarctica colonies. Distinct features of their carbohydrate, nitrogen, sulfur and iron metabolisms may serve to support mutualistic relationships with P. antarctica. The SAR92 genome indicates a specialization in the degradation of fatty acids and dimethylsulfoniopropionate (compounds released by P. antarctica) into dimethyl sulfide, an aerosol precursor. The Oceanospirillaceae genome carries genes that may enhance algal physiology (cobalamin synthesis). Finally, the Cryomorphaceae genome is enriched in genes that function in cell or colony invasion. A novel pico-eukaryote, Micromonas related genome (19.6 Mb, ~94% completion) was also recovered. It contains the gene for an anti-freeze protein, which is lacking in Micromonas at lower latitudes. These draft genomes are representative for abundant microbial taxa across the Southern Ocean surface.
    Description: This work was performed with financial support from NSF Antarctic Sciences awards ANT-1142095 to AP.
    Keywords: Southern Ocean ; Amundsen Sea Polynya ; Phytoplankton bloom ; Phaeocystis ; Micromonas ; Microbial communities ; Metagenomics ; Genome reconstruction
    Repository Name: Woods Hole Open Access Server
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