Table of Contents

• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

Radium isotope data summaries from AMLR and NBP cruises to the Antarctic in 2006

Naturally occurring radium isotopes (224Ra, 226Ra, 228Ra) were used in determining
lateral mixing processes which are reported in dpm/m3.
 

Cruises

AMLR (Antarctic Marine Living Resources) R/V Yuzhmorgeologiya Jan2006:
The research program was focused in the southern Drake Passage
along the Shackelton Shelf located near the Bransfield Strait.
Samples were obtained from the R/V Yuzhmorgeologiya and inflatables
that were taken to island locations.
Lat/Lon Bounding Box
-62.2538Lat, -62.9966Lon
-63.2335Lat, -59.0332Lon
-59.9964Lat, -55.7612Lon
-61.4995Lat, -53.9996Lon

NBP (Nathaniel B. Palmer) R/V Nathaniel B. Palmer July2006:
The research was conducted in the same region of the Drake Passage as the AMLR cruise.
Samples were obtained aboard the R/V Nathaniel B. Palmer
Lat/Lon bounding box
-60.4991Lat, -58.5613Lon
-62.3599Lat, -58.0392Lon
-60.2783Lat, -57.4509Lon
-61.2683Lat, -54.2852Lon
 

Associated Publications

Brzezinski, M.A., Nelson, D.M., Franck, V.M. and Sigmon, D.E., 2001. "Silicon dynamics within an intense open-ocean diatom bloom in the pacific sector of the southern ocean." Deep-Sea Research Part II 48, pp. 3997-4018

Michiel Rutgers van der Loeff, Manmohan M. Sarin, Mark Baskaran, Claudia Benitez-Nelson, Ken O. Buesseler, Matt Charette, Minhan Dai, Örjan Gustafsson, Pere Masque, Paul J. Morris, Kent Orlandini, Alessia Rodriguez y Baena, Nicolas Savoye, Sabine Schmidt, Robert Turnewitsch, Ingrid Vöge, James T. Waples. "A review of present techniques and methodological advances in analyzing 234Th in aquatic systems" Marine Chemistry, Volume 100, Issues 3-4, 1 August 2006, Pages 190-212

Pike, S.M., K.O. Buesseler, J. Andrews and N. Savoye, 2005. "Quantification of 234Th recovery in small volume sea water samples by inductively coupled plasma mass spectrometry." (PDF) Journal of Radioanalytical and Nuclear Chemistry, 263(2): 355-360.

Willard S. Moore and Ralph Arnold (1996). "Measurement of 223Ra and 224Ra in coastal waters using a delayed coincidence counter." Journal of Geophysical Research, vol. 101, no. c1, pages 1321-1329, January 15, 1996.

Sampling and Analytical Methodology

Surface water samples were collected from the ships clean water intake (AMLR and NBP), and measured for 223Ra and 224Ra activities following standard methods of extraction and delayed coincidence counting (Moore and Arnold, 1996). 300 liters was collected per sample on the AMLR cruise while 558 liters of water was collected during the winter NBP cruise. Ra isotopes were extracted at sea onto manganese oxide-impregnated acrylic fiber at flow rates less than 1 L per minute. Recovery rates have been shown to be greater than 95%. The Mn-fiber was rinsed with deionized water, partially dried, and analyzed for 223Ra and 224Ra using the RaDeCC delayed coincidence counter. Moore and Arnold, 1996 W.S. Moore and R. Arnold, Measurement of Ra-223 and Ra-224 in coastal waters using a delayed coincidence counter, Journal of Geophysical Research - Oceans 101 (C1) (1996), pp. 1321-1329. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (89) Long-lived isotopes (226Ra, 228Ra) were subsequently determined through measurement on a Canaberra gamma detector. This was conducted on the same fibers after they were ashed in a muffle furnace. The detector was calibrated using Mn-fiber standards prepared in the same geometry as the samples .
 

Data Processing

CHN: Linear regression of standards is used to determine the carbon content of the sample

Ra: Radium concentrations are determined by the Radecc coincidence counters.
Corrections are to made to account for detector efficiency, radioactive decay, and ingrowth.

Modifications to original data made to conform to BCO-DMO database convention

Cruise_ID added
+/- columns eliminated and error served as separate column for each data type
empty cells filled with "nd" (no data)
Latitude/Longitude headers converted to lat/lon
date reformatted to YYYYMMDD
time reformatted to HHMM
decimal data values padded to consistent decimal places

Collaborative Research: Plankton Community Structure and Iron Distribution in the
Southern Drake Passage and Scotia Sea

The Shackleton Fracture Zone (SFZ) in Drake Passage of the Southern Ocean defines a
boundary between low and high phytoplankton waters. Low chlorophyll water flowing
through the southern Drake Passage emerges as high chlorophyll water to the east,
and recent evidence indicates that the Southern Antarctic Circumpolar Current Front
(SACCF) is steered south of the SFZ onto the Antarctic Peninsula shelf where mixing
between the water types occurs. The mixed water is then advected off-shelf with
elevatediron and phytoplankton biomass.

The SFZ is therefore an ideal natural laboratory to improve the understanding of
plankton community responses to natural iron fertilization, and how these processes
influence export of organic carbon to the ocean interior. The bathymetry of the region
is hypothesized to influence mesoscale circulation and transport of iron, leading to
the observed patterns in phytoplankton biomass.

The position of the Antarctic Circumpolar Current (ACC) is further hypothesized to
influence the magnitude of the flow of ACC water onto the peninsula shelf, mediating
the amount of iron transported into the Scotia Sea. To address these hypotheses, a
research cruise will be conducted near the SFZ and to the east in the southern Scotia
Sea. A mesoscale station grid for vertical profiles, water sampling, and bottle incubation
enrichment experiments will complement rapid surface surveys of chemical, plankton, and
hydrographic properties. Distributions of manganese, aluminum and radium isotopes will
be determined to trace iron sources and estimate mixing rates.

Phytoplankton and bacterial physiological states (including responses to iron enrichment)
and the structure of the plankton communities will be studied. The primary goal is to
better understand how plankton productivity, community structure and export production
in the Southern Ocean are affected by the coupling between bathymetry, mesoscale circulation,
and distributions of limiting nutrients. The proposed work represents an interdisciplinary
approach to address the fundamental physical, chemical and biological processes that
contribute to the abrupt transition in chl-a which occurs near the SFZ. Given recent
indications that the Southern Ocean is warming, it is important to advance the understanding
of conditions that regulate the present ecosystem structure in order to predict the effects
of climate variability. This project will promote training and learning across a broad
spectrum of groups. Funds are included to support postdocs, graduate students, and
undergraduates. In addition, this project will contribute to the development of content
for the Polar Science Station website, which has been a resource since 2001 for instructors
and students in adult education, home schooling, tribal schools, corrections education,
family literacy programs, and the general public.

Radium and Thorium isotope data summaries from AMLR and NBP cruises to the Antarctic in 2006

Naturally occurring radium isotopes (224Ra, 226Ra, 228Ra) were used in determining
lateral mixing processes which are reported in dpm/m3.

Particulate organic Carbon (POC) flux was determined through measuring Thorium (234Th) reported in dpm/kg.

Cruises

AMLR (Antarctic Marine Living Resources) R/V Yuzhmorgeologiya Jan/2006:
The research program was focused in the southern Drake Passage
along the Shackelton Shelf located near the Bransfield Strait.
Samples were obtained from the R/V Yuzhmorgeologiya and inflatables
that were taken to island locations.
Lat/Lon Bounding Box
-62.2538Lat, -62.9966Lon
-63.2335Lat, -59.0332Lon
-59.9964Lat, -55.7612Lon
-61.4995Lat, -53.9996Lon

NBP (Nathaniel B. Palmer) R/V Nathaniel B. Palmer July/2006:
The research was conducted in the same region of the Drake Passage as the AMLR cruise.
Samples were obtained aboard the R/V Nathaniel B. Palmer
Lat/Lon bounding box
-60.4991Lat, -58.5613Lon
-62.3599Lat, -58.0392Lon
-60.2783Lat, -57.4509Lon
-61.2683Lat, -54.2852Lon

NASA GCMD Link: NASA GCMD

NSF Proposal Title: Collaborative Research: Plankton Community Structure and Iron Distribution in the Southern Drake Passage and Scotia Sea

The Shackleton Fracture Zone (SFZ) in Drake Passage of the Southern Ocean defines a boundary between low and high phytoplankton waters. Low chlorophyll water flowing through the southern Drake Passage emerges as high chlorophyll water to the east, and recent evidence indicates that the Southern Antarctic Circumpolar Current Front (SACCF) is steered south of the SFZ onto the Antarctic Peninsula shelf where mixing between the water types occurs. The mixed water is then advected off-shelf with elevated iron and phytoplankton biomass. The SFZ is therefore an ideal natural laboratory to improve the understanding of plankton community responses to natural iron fertilization, and how these processes influence export of organic carbon to the ocean interior. The bathymetry of the region is hypothesized to influence mesoscale circulation and transport of iron, leading to the observed patterns in phytoplankton biomass. The position of the Antarctic Circumpolar Current (ACC) is further hypothesized to influence the magnitude of the flow of ACC water onto the peninsula shelf, mediating the amount of iron transported into the Scotia Sea. To address these hypotheses, a research cruise will be conducted near the SFZ and to the east in the southern Scotia Sea. A mesoscale station grid for vertical profiles, water sampling, and bottle incubation enrichment experiments will complement rapid surface surveys of chemical, plankton, and hydrographic properties. Distributions of manganese, aluminum and radium isotopes will be determined to trace iron sources and estimate mixing rates. Phytoplankton and bacterial physiological states (including responses to iron enrichment) and the structure of the plankton communities will be studied. The primary goal is to better understand how plankton productivity, community structure and export production in the Southern Ocean are affected by the coupling between bathymetry, mesoscale circulation, and distributions of limiting nutrients. The proposed work represents an interdisciplinary approach to address the fundamental physical, chemical and biological processes that contribute to the abrupt transition in chl-a which occurs near the SFZ. Given recent indications that the Southern Ocean is warming, it is important to advance the understanding of conditions that regulate the present ecosystem structure in order to predict the effects of climate variability. This project will promote training and learning across a broad spectrum of groups. Funds are included to support postdocs, graduate students, and undergraduates. In addition, this project will contribute to the development of content for the Polar Science Station website, which has been a resource since 2001 for instructors and students in adult education, home schooling, tribal schools, corrections education, family literacy programs, and the general public.

PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH

Hewes, C. D., Reiss, C.S., .Kahru, M. , Mitchell, B.G. , and Holm-Hansen, O.. "Control of phytoplankton biomass by dilution and mixed layer depth in the western Weddell-Scotia Confluence (WSC)," Marine Ecology Progress Series, v.366, 2008, p. 15.

Hiscock, M. , Lance, V. , Apprill, A., Bidigare, R , Mitchell, B., Smith Jr. W., Barber, R.. "Photosynthetic maximum quantum yield increases are an essential component of the Southern Ocean phytoplankton response to iron," Proceedings of the National Academy of Sciences, v.105(2), 2008, p. 4775.

Holm-Hansen, O., Kahru, M., Hewes, C.. "Deep chlorophyll a maxima (DCMs) in pelagic Antarctic waters. II. Relation to bathymetric features and dissolved iron concentrations," Marine Ecology-Progress Series, v.297, 2005, p. 71.

Hopkinson, B., Mitchell, B. G., Reynolds, R. A., Wang, H., Selph, K., Measures, C., Hewes, C., Holm-Hansen, O., Barbeau, K.. "Iron limitation Across Chlorophyll Gradients in the Southern Drake Passage: Phytoplankton Responses to Iron Addition and Photosynthetic Indicators of Iron Stress," Limnology and Oceanography, 2007, p. 2540.

Hopkinson, B., Mitchell, B. G., Reynolds, R. A., Wang, H., Selph, K., Measures, C., Hewes, C., Holm-Hansen, O., Barbeau, K.. "Iron limitation Across Chlorophyll Gradients in the Southern Drake Passage: Phytoplankton Responses to Iron Addition and Photosynthetic Indicators of Iron Stress," Limnology and Oceanography, v.52, 2007, p. 2540.

Kahru, M., Mitchell, B. G., Gille, S. T., Hewes, C. D. and Holm-Hansen, O.. "Eddies enhance biological production in the Weddell-Scotia Confluence of the Southern Ocean," Geophys. Res. Let., 34,, v.24, 2007, p. L14603.