Natural Iron Enrichment
Occurring to a measurable extent in coastal upwelling zones, certain
processes control the transformation of resuspended iron into bioavailable
iron. The "natural iron enrichment experiment" looked at
the entrainment in upwelled water of iron-rich sediment from the
continental shelf. This iron is important to phytoplankton growth,
but only two previous experiments have tracked it. The ability to
map in real time both metal and nutrient concentrations in an advecting
patch of upwelled water suggested the need for Lagrangian drifters to
measure both physical and chemical properties of the patch. Therefore,
measurements of particulate and dissolved iron were made from an
ultra-clean seawater intake towfish aboard the R/V New Horizon and
dissolvable iron concentrations were measured
continuously at the sea surface and particulate iron concentrations were
determined daily, the drifter measured the important physical and
biological properties of the same water.
A Seabird SBE37 Microcat CTD and a Hobilabs Hydroscat-2 (HS2)
were attached to an instrument cage 1 meter below
the surface on a drifter buoy. The HS2 measured optical backscatter at 470 and
676 nanometers, as well as fluorescence at 676 nanometers.
A Satlantic OCR-100 radiometer measuring upwelled radiance (Lu) at SeaWiFS
wavelengths and a Ed-20 radiometer measuring surface incident irradiance (Es)
at 490 nm were deployed on the D1 drifter. The OCR-100 was mounted on a cage
1 meter below the drifter float.
The location of the D1 drifter was sampled via GPS. This dataset was measured
during the MUSE experiment from MBARI's D1 drifter deployed along the coast
of California just north of Monterey Bay.