Highly variable iron content modulates iceberg-ocean fertilisation and potential carbon export.

Area of Science:

• Oceanography
• Marine Biology
• Climate Science

Background:

• Marine phytoplankton growth in high-latitude oceans is primarily limited by iron availability.
• Icebergs act as crucial transporters of iron, a vital micronutrient, into polar marine ecosystems.
• Rising global temperatures may increase iceberg flux, potentially boosting marine productivity and carbon export, thus creating a negative climate feedback loop.

Purpose of the Study:

• To quantify the magnitude of iron flux from icebergs to polar oceans.
• To assess the impact of iceberg-derived iron on marine productivity and carbon export.
• To understand how changing iceberg characteristics influence ocean iron enrichment.

Main Methods:

• Global analysis of iron concentrations in iceberg samples.
• Investigating the heterogeneous distribution of iron within ice.
• Modeling the effects of iceberg melt dynamics on iron delivery.

Main Results:

• Iceberg iron concentrations exhibit a vast range, varying over six orders of magnitude.
• Despite being the largest iron source, heterogeneous iron distribution in ice moderates its delivery to offshore waters.
• Ocean iron enrichment is influenced by the complex interplay of iceberg properties and melt processes.

Conclusions:

• While increased iceberg flux may enhance marine productivity, the heterogeneous iron content and distribution within ice are critical moderating factors.
• Future changes in marine productivity will depend not only on the total volume of icebergs but also on their specific properties, sediment content, and melt dynamics.
• Understanding these complexities is essential for accurately predicting the impact of climate change on polar ocean ecosystems and carbon cycling.