Title of article :
Nitrogen fixation amplifies the ocean biogeochemical response to decadal timescale variations in mineral dust deposition
Author/Authors :
By J. KEITH MOORE، نويسنده , , SCOTT C. DONEY ، نويسنده , , Keith Lindsay، نويسنده , , NATALIE MAHOWALD ، نويسنده , , ANTHONY F. MICHAELS، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2006
Abstract :
global ocean biogeochemical model is used to quantify the sensitivity of marine biogeochemistry and air–sea CO2
exchange to variations in dust deposition over decadal timescales. Estimates of dust deposition generated under four
climate states provide a large range in total deposition with spatially realistic patterns; transient ocean model experiments
are conducted by applying a step-function change in deposition from a current climate control. Relative to current
conditions, higher dust deposition increases diatom and export production, nitrogen fixation and oceanic net CO2
uptake from the atmosphere, while reduced dust deposition has the opposite effects. Over timescales less than a decade,
dust modulation of marine productivity and export is dominated by direct effects in high-nutrient, low-chlorophyll
regions, where iron is the primary limiting nutrient. On longer timescales, an indirect nitrogen fixation pathway has
increased importance, significantly amplifying the ocean biogeochemical response. Because dust iron input decouples
carbon cycling from subsurface macronutrient supply, the ratio of the change in net ocean CO2 uptake to change in
export flux is large, 0.45–0.6. Decreasing dust deposition and reduced oceanic CO2 uptake over the next century could
provide a positive feedback to global warming, distinct from feedbacks associated with changes in stratification and
circulation
Journal title :
Tellus.Series B
Journal title :
Tellus.Series B