A global compilation of dissolved iron measurements: focus on distributions and processes in the Southern Ocean

A data synthesis effort recently compiled over 13,000 observations of dissolved iron concentrations that more than doubled the previous data compilation. A systematic analysis of the distribution of data in the Southern Ocean was performed using four regions, six basins and five depth intervals as a framework. Substantial variability in the depth dependent trends were found between different basins and regions, which were indicative of the possible underlying influence of ocean physics, chemistry and biology. Alessandro Tagliabue’s and co-authors (Tagliabue, et al. 2012) analysis was able to highlight where observations are lacking in a particular region or time of year, which they hope will assist future sampling efforts. Overall, more observations have been collected in the past 5 years under the auspices of the International Polar Year and GEOTRACES efforts than were collected in the prior ~15 years. Nevertheless, despite this progress the seasonal cycle of iron that can be extracted from the well-sampled region south of Tasmania remains enigmatic. From over 160 observations, they find little evidence of ‘winter recharge’ in iron concentrations and instead find the highest iron concentrations to be coincident with the highest phytoplankton biomass levels. This might reflect gaps in seasonal sampling between July and November or the influence of the so-called ‘ferrous wheel’ in driving the recycling of iron. This clearly highlights the need for more measurements of iron at ‘seasonal transitions’, even in well-sampled areas.

This dataset will prove useful for other regional synthesis studies or the evaluation of ocean biogeochemical models. It continues to be maintained by A. Tagliabue and is available from GEOTRACES Data Assembly Center web site or http://pcwww.liv.ac.uk/~atagliab.

Tagliabue highlight

Figure: Box and whisker plot of the seasonal cycle of dFe in the upper 100m for the Subantarctic SR3 (164 total observations from 1995–2008). The SR3 region is defined as that south of 45° S and encompassing 135° E to 155° E, with the Subantarctic and zone isolated using the mean local position of the Polar Front. The size of the box represents the 1st to 3rd quartiles, with the vertical bar corresponding to the median and the whiskers representing 1.5 times the inter-quartile range.



Tagliabue, A., et al. (2012) A global compilation of dissolved iron measurements: focus on distributions and processes in the Southern Ocean, Biogeosciences, 9, 2333-2349, doi:10.5194/bg-9-2333-2012. Click here to access the paper.

Latest highlights

Science Highlights

Controls of cadmium-phosphate systematic unraveled by Neural Networks and Ocean Circulation Inverse Model

Roshan and DeVries explore the similarities and contrasts between oceanic cadmium and phosphate cycles using an Artificial Neural Network mapping technique and Ocean Circulation Inverse Model.


Science Highlights

Retreat of large marine-terminating glaciers may increase iron supply to surface waters

The findings demonstrate that glacial retreat and loss of ice-shelves may potentially result in increases in dissolved Fe supply to surface waters downstream of large marine terminating glaciers in future.


Science Highlights

A new and more quantitative atlas of the deep-sea burial fluxes of major and trace elements

Among other findings, authors find that the new opal flux is roughly a factor of two increase over previous estimates having important implications for the global silicon cycle.


Science Highlights

Updated compilation of the global continental and marine lithogenic neodymium isotopic measurements

This new compilation and gridded datasets offer a concrete way forward to improve the application of neodymium isotopes as a useful tracer of ocean circulation.