Publikationsdatum:
2014-04-14
Beschreibung:
In high-nutrient low-chlorophyll waters of the
western Atlantic sector of the Southern Ocean, an intense
phytoplankton bloom is observed annually north of South
Georgia. Multiple sources, including shallow sediments and
atmospheric dust deposition, are thought to introduce iron to
the region. However, the relative importance of each source
is still unclear, owing in part to the scarcity of dissolved
iron (dFe) measurements in the South Georgia region. In this
study, we combine results from a recently published dFe data
set around South Georgia with a coupled regional hydrodynamic
and biogeochemical model to further investigate iron
supply around the island. The biogeochemical component of
the model includes an iron cycle, where sediments and dust
deposition are the sources of iron to the ocean. The model
captures the characteristic flow patterns around South Georgia,
hence simulating a large phytoplankton bloom to the
north (i.e. downstream) of the island. Modelled dFe concentrations
agree well with observations (mean difference and
root mean square errors of �0.02nM and �0.81 nM) and
form a large plume to the north of the island that extends eastwards
for more than 800 km. In agreement with observations,
highest dFe concentrations are located along the coast and
decrease with distance from the island. Sensitivity tests indicate
that most of the iron measured in the main bloom area
originates from the coast and very shallow shelf-sediments
(depths 〈 20 m). Dust deposition exerts almost no effect on
surface chlorophyll a concentrations. Other sources of iron
such as run-off and glacial melt are not represented explicitly
in the model, however we discuss their role in the local
iron budget.
Repository-Name:
EPIC Alfred Wegener Institut
Materialart:
Article
,
isiRev
,
info:eu-repo/semantics/article
Format:
application/pdf
