wAbstract
@Estimates of glacial sediment delivery to the oceans have been
derived from fluxes of meltwater runoff and iceberg calving, and
their sediment loads. The combined total (2900 Tg yr-1)
of the suspended sediment load in meltwaters (1400 Tg yr-1)
and the sediment delivered by icebergs (1500 Tg yr-1)
are within the range of earlier estimates. High-resolution microscopic
observations show that suspended sediments from glacial meltwaters,
supraglacial, and proglacial sediments, and sediments in basal
ice, from Arctic, Alpine, and Antarctic locations all contain
iron (oxyhydr)oxide nanoparticles, which are poorly crystalline,
typically `5 nm in diameter, and which occur as single grains
or aggregates that may be isolated or attached to sediment grains.
Nanoparticles with these characteristics are potentially bioavailable.
A global model comparing the sources and sinks of iron present
as (oxyhydr)oxides indicates that sediment delivered by icebergs
is a significant source of iron to the open oceans, beyond the
continental shelf. Iceberg delivery of sediment containing iron
as (oxyhydr)oxides during the Last Glacial Maximum may have been
sufficient to fertilise the increase in oceanic productivity required
to drawdown atmospheric CO2 to the levels
observed in ice cores.x
1. Introduction
2. Methods
3. Estimation of the glacially derived sediment flux
@3.1. Previous approaches
@3.2. Estimation of glacial fluxes
4. Nanoparticulate morphologies and surface interactions
@4.1. Previous observations
@4.2. Morphology of iron (oxyhydr)oxides in glacial sediments
@4.3. Interactions of iron (oxyhydr)oxide nanoparticulates in
seawater
5. The global iron (oxyhydr)oxide cycle
@5.1. Riverine fluxes
@5.2. Groundwater fluxes
@5.3. Coastal erosion
@5.4. Hydrothermal flux
@5.5. Glacial flux
@5.6. Aeolian dust
@5.7. Diagenetic recycling
@5.8. The global iron (oxyhydr)oxide cycle
6. Conclusions
Acknowledgments
References
 Fig. 5. The global iron (oxyhydr)oxide cycle. Units in Tg yr-1. kRaiswell,R., Tranter,M., Benning,L.G., Siegert,M., De'ath,R., Huybrechts,P. and Payne,T.(2006): Contributions from glacially derived sediment to the global iron (oxyhydr)oxide cycle: Implications for iron delivery to the oceans. Geochimica et Cosmochimica Acta, 70, 2765-2780.©ηl |