Science Highlights

Why did the concentration of atmospheric carbon dioxide rise so much and so quickly during the last deglaciation? 

During the Last Glacial Maximum, the deep southern Pacific waters were stratified, efficiently accumulating old, CO2 rich waters. Basak and co-authors (2018, see reference below) measured neodymium isotopes in sediment cores that clearly show that when these deep waters became less stratified as the climate warmed they released their carbon which could escape to the atmosphere...what a tempting prospect and beautiful teaser for the forthcoming PAGES-GEOTRACES workshop of December 2018!

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Figure: View from RV Polarstern while collecting sediment samples used in the study by Basak et al.
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Credit: Dr. Katharina Pahnke


Basak, C., Fröllje, H., Lamy, F., Gersonde, R., Benz, V., Anderson, R. F., Molina-Kescher, M., Pahnke, K. (2018). Breakup of last glacial deep stratification in the South Pacific. Science, 359(6378), 900–904.

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Particle distribution in repeated ocean sections and sediment resuspension

This is the first compilation of an expansive data base of transmissometer data on a decadal period of time. More than 7376 stations have been analyzed for “cp” value, a proxy for particle concentrations, by Gardner and co-workers (2018, see reference below). Full water-column sections confirm that particle concentrations are higher in surface waters, decrease rapidly below 200 m, most often down to the seafloor. However, cloudy near-bottom waters, known as “benthic nepheloid layers”, are generated by sediment erosion and resuspension at specific geographic areas. These locations are directly linked to energetic surface dynamics that produce regions of high Eddy Kinetic Energy (EKE). More fascinating, however, is the decadal persistence of this close surface-to-deep connection. We invite you to read this very interesting article!

18 Gardner2Figures: (A) Map of log of surface eddy kinetic energy (modified from Dixon et al., 2011) with cp transects indicated. (B) Section of cp (proxy for particle concentration) along 53° W in spring, 2012 in the Western North Atlantic. Black contours are dissolved oxygen (µmol kg-1). Click here to view the figure larger.


Gardner, W. D., Mishonov, A. V., & Richardson, M. J. (2018). Decadal Comparisons of Particulate Matter in Repeat Transects in the Atlantic, Pacific, and Indian Ocean Basins. Geophysical Research Letters.

Climate change induced spectacular increase of the land-ocean inputs in the Arctic Ocean

Measurements of radium-228 (228Ra) in the framework of the 2015 U.S. GEOTRACES Arctic Transect (GN01), revealed that the surface water content of this tracer has almost doubled over the last decade, specifically in the Transpolar Drift near the North Pole.

Radium isotopes are excellent tracers of land-ocean inputs. A mass balance model for 228Ra allowed Kipp and co-workers (2018, see reference below) to suggest that this increase is due to an intensification of shelf-derived material inputs to the central basin. These coastal changes, in turn, could also be delivering more nutrients, carbon, and other chemicals into the Arctic Ocean and lead to dramatic impacts on Arctic food webs and animal populations.

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Figure: Diminishing sea ice near the Arctic coast leaves more open water near the coast for winds to create waves. The increased wave action reaches down and stirs up sediments on shallow continental shelves, releasing radium and other chemicals that are carried up to the surface and swept away into the open ocean by currents such as the Transpolar Drift. Artwork: Natalie Renier, Woods Hole Oceanographic Institution. Please click here to view the figure larger.


Kipp, L. E., Charette, M. A., Moore, W. S., Henderson, P. B., & Rigor, I. G. (2018). Increased fluxes of shelf-derived materials to the central Arctic Ocean. Science Advances, 4(1), eaao1302. DOI:

Where, how and which trace elements are released from dust at the sea surface?

Alex Baker and Tim Jickells (2017, see reference below) propose to answer to this question thanks to analysis of aerosols collected in the framework of the Atlantic Meridional Transect (AMT). They established the soluble concentrations of a range of trace metals (iron, aluminium, manganese, titanium, zinc, vanadium, nickel and copper) and major ions. They reveal much higher inputs to the North Atlantic Ocean compared to the South Atlantic Ocean, reflecting stronger land based emission sources in the Northern Hemisphere. Comparison of these inputs with the surface water contents of the same trace metals compiled in the GEOTRACES intermediate data product show surprising features that you will discover if you read this paper…

18 Baker lowFigures: (A) Approximate tracks of the AMT cruises (dots and triangles) and general flow directions of the seven major atmospheric transport routes encountered during the cruises (arrows). Abbreviations for the air transport regimes are: continental Europe (EUR), North Africa including the Sahara and Sahel: (SAH), Southern Africa impacted by biomass burning emissions (SAB), Southern Africa not impacted by biomass burning (SAF), South America (SAM), remote North or South Atlantic i.e. not crossing land for at least 5 days prior to collection (RNA and RSA respectively). (B) Box and whisker plots showing the variations in the concentrations of iron, aluminium, manganese, titanium, zinc, vanadium, nickel and copper with air transport/source type for the AMT transect. They reveal much higher inputs to the North Atlantic Ocean, reflecting stronger land based emission sources in the Northern Hemisphere. Please click here to view the figure larger. (Figures modified from Progress in Oceanography)


Baker, A. R., & Jickells, T. D. (2017). Atmospheric deposition of soluble trace elements along the Atlantic Meridional Transect (AMT). Progress in Oceanography, 158, 41–51.

Dissolved zinc and silicate decoupling in the North Pacific Ocean

Large-scale distributions of dissolved zinc (Zn) in the western and central subarctic North Pacific Ocean was established as part of the North Pacific GEOTRACES section GP02. Kim and co-workers could figure out interesting Zn behavior in this area:

  • Decoupling between Zn and Silicate in the intermediate water,

  • Zn* values (used to show the variability in the relationship between dissolved Zn and silicate in the ocean) are strongly positive in the intermediate waters of the western and central subarctic North Pacific,

  • Dissolved Zn and soluble reactive phosphorus (SRP) concentrations were relatively high in the intermediate water.

The authors suggest that these particular values observed in the intermediate waters of the subarctic North Pacific result of remineralization from Zn-rich biogenic particles, weak reversible scavenging onto sinking biogenic particles, and sedimentary Zn sources. 

17 KimlFigure: (A) Locations of sampling stations in the subarctic North Pacific. (B) Relationships between dissolved Zn and silicate. (C) Zn* as a function of density. The shaded bar represents density range of the intermediate water (26.6–27.5 σθ). (D) Relationships between dissolved Zn and SRP. In (B) and (D), green, red, and black indicate shallow water, intermediate water, and deep water in the subarctic North Pacific, respectively, while blue indicates data from the subtropical North Pacific. Click here to view the figure larger.


Kim, T., Obata, H., Nishioka, J., & Gamo, T. (2017). Distribution of Dissolved Zinc in the Western and Central Subarctic North Pacific. Global Biogeochemical Cycles, 31(9), 1454–1468. DOI:

 Data Product (IDP2017)


 Data Assembly Centre (GDAC)


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