Wind blown dust as an ocean fertilizer for CDR
Tom Goreau
Some claim wind-blown dust, or at least its iron component, is a major ocean fertilizer, and that dumping these in the ocean will cause massive phytoplankton blooms, removing carbon dioxide that they claim will vanish as organic carbon into the deep sea (completely ignoring the biological fact that this primary productivity will be internally recycled up to hundreds of times within the system before it escapes).
Atmospheric Nourishment of Global Ocean Ecosystems, 2023, Westberry, Behrenfeld, Shi, Yu, Remer, & Bian, Science, 380:515-519, quantifies linkages between dust inputs and ocean productivity by global mapping of chlorophyll, phytoplankton biomass, and wind-blown dust inputs:
Abstract
Over the vast open ocean, vital nutrients for phytoplankton growth in the sunlit surface layer are largely provided through physical transport from deep waters, but some nutrients are also provided through atmospheric deposition of desert dust. The extent and magnitude of dust-mediated effects on surface ocean ecosystems have been difficult to estimate globally. In this work, we use global satellite ocean color products to demonstrate widespread responses to atmospheric dust deposition across a diverse continuum of phytoplankton nutritional conditions. The observed responses vary regionally, with some areas exhibiting substantial changes in phytoplankton biomass, whereas in other areas, the response reflects a change in physiological status or health. Climate-driven changes in atmospheric aerosols will alter the relative importance of this nutrient source.
They find that about 4.5% of global primary production is related to wind-blown (aeolian) inputs, and the rest is due to upwelling of deep sea nutrients, so the dust signal is very small globally (although much more significant in local areas immediately down-wind from major sources). Much more sediment enters the ocean from rivers than winds, but coastal areas have excess iron, and there sediment acts not as a fertilizer but as an inhibitor of photosynthesis by blocking light.
This study’s results suggests that wind-blown inputs would need to increase at least 10 times over present levels to become a co-dominant source of nutrients. During the last Ice Age, global biomass dropped to about half the present level, and wind-blown erosion of dust to the sea greatly increased, as documented in deep sea cores. Humans have already destroyed about half of the biomass on earth, turned forests into grasslands by intensive burning, and caused massive wind-blown soil erosion by deforestation, so we have already increased wind-blown erosion inputs to the ocean very significantly. Increasing dust or iron enough to make a big CDR difference will be very challenging, even if the local iron limitation hypothesis is correct.
Thomas J. F. Goreau, PhD
President, Global Coral Reef Alliance
Chief Scientist, Blue Regeneration SL
President, Biorock Technology Inc.
Technical Advisor, Blue Guardians Programme, SIDS DOCK
37 Pleasant Street, Cambridge, MA 02139
gor...@globalcoral.org
www.globalcoral.org
Skype: tomgoreau
Tel: (1) 617-864-4226 (leave message)
Books:
Geotherapy: Innovative Methods of Soil Fertility Restoration, Carbon Sequestration, and Reversing CO2 Increase
http://www.crcpress.com/product/isbn/9781466595392
Innovative Methods of Marine Ecosystem Restoration
http://www.crcpress.com/product/isbn/9781466557734
No one can change the past, everybody can change the future
It’s much later than we think, especially if we don’t think
Those with their heads in the sand will see the light when global warming and sea level rise wash the beach away
Geotherapy: Regenerating ecosystem services to reverse climate change
