Approaches Ocean fertilization

1 approaches

1.1 iron
1.2 phosphorus
1.3 nitrogen
1.4 pelagic pumping[edit | edit source]
1.5 volcanic ash

approaches

ocean fertilisation options worthwhile if sustained on millennial timescale , phosphorus addition may have greater long-term potential iron or nitrogen fertilisation. phytoplankton require variety of nutrients. these include macronutrients such nitrate , phosphate (in relatively high concentrations) , micronutrients such iron , zinc (in smaller quantities). nutrient requirements vary across phylogenetic groups (e.g., diatoms require silicon) may not individually limit total biomass production. co-limitation (among multiple nutrients) may mean 1 nutrient can partially compensate shortage of another. silicon not affect total production, can change timing , community structure follow-on effects on remineralization times , subsequent mesopelagic.nutrient vertical distribution.

low-nutrient low-chlorophyll (lnlc) waters occupy oceans subtropical gyre systems, approximately 40 per cent of surface, wind-driven downwelling , strong thermocline impede nutrient resupply deeper water. nitrogen fixation cyanobacteria provides major source of n. in effect, prevents ocean losing n required photosynthesis. phosphorus has no substantial supply route, making ultimate limiting macronutrient. sources fuel primary production deep water stocks , runoff or dust-based.

iron

approximately 25 per cent of ocean surface has ample macronutrients, little plant biomass (as defined chlorophyll). production in these high-nutrient low-chlorophyll (hnlc) waters limited micronutrients iron. cost of distributing iron on large ocean areas large compared expected value of carbon credits.

phosphorus

where phosphate limiting nutrient in photic zone, addition of phosphate expected increase primary phytoplankton production. technique can give 0.83w/m of globally averaged negative forcing, sufficient reverse warming effect of half current levels of anthropogenic co

2 emissions. 1 water-soluble fertilizer diammonium phosphate (dap), (nh

4)

2hpo

4, of 2008 had market price of 1700/tonne−1 of phosphorus. using price , c : p redfield ratio of 106 : 1 produces sequestration cost (excluding preparation , injection costs) of $45 /tonne of carbon (2008), substantially less trading price carbon emissions.

nitrogen

this technique (proposed ian jones) proposes fertilize ocean urea, nitrogen rich substance, encourage phytoplankton growth. has been considered karl. concentrations of macronutrients per area of ocean surface similar large natural upwellings. once exported surface, carbon remains sequestered long time.

an australian company, ocean nourishment corporation (onc), planned inject hundreds of tonnes of urea ocean, in order boost growth of co

2-absorbing phytoplankton, way combat climate change. in 2007, sydney-based onc completed experiment involving 1 tonne of nitrogen in sulu sea off philippines.

macronutrient nourishment can give 0.38w/m of globally averaged negative forcing, sufficient reverse warming effect of current levels of around quarter of anthropogenic co

2 emissions.

the ocean nourishment corporation claimed, 1 ocean nourishment plant remove approximately 5-8 million tonnes of co2 atmosphere each year of operation, equivalent offsetting annual emissions typical 1200 mw coal-fired power station or short-term sequestration 1 million hectares of new growth forest .

the 2 dominant costs manufacturing nitrogen , nutrient delivery.

pelagic pumping[edit | edit source]

local wave power used pump nutrient-rich water hundred- metre-plus depths euphotic zone. however, deep water concentrations of dissolved co2 returned atmosphere.

the supply of dic in upwelled water sufficient photosynthesis permitted upwelled nutrients, without requiring atmospheric co2. second-order effects include how composition of upwelled water differs of settling particles. more nitrogen carbon remineralized sinking organic material. upwelling of water allows more carbon sink in upwelled water, make room @ least atmospheric co2 absorbed. magnitude of difference unclear. no comprehensive studies have yet resolved question. preliminary calculations using upper limit assumptions indicate low value. 1,000 square kilometres (390 sq mi) sequester 1 gigatonne/year.

sequestration depends on upward flux , rate of lateral surface mixing of surface water denser pumped water.

volcanic ash

volcanic ash adds nutrients surface ocean. apparent in nutrient-limited areas. research on effects of anthropogenic , aeolian iron addition ocean surface suggests nutrient-limited areas benefit combination of nutrients provided anthropogenic, eolian , volcanic deposition. oceanic areas comparably limited in more 1 nutrient, fertilization regimes includes limited nutrients more succeed. volcanic ash supplies multiple nutrients system, excess metal ions can harmful. positive impacts of volcanic ash deposition potentially outweighed potential harm.

clear evidence documents ash can as 45 percent weight in deep marine sediments. in pacific ocean estimates claim (on millennial-scale) atmospheric deposition of air-fall volcanic ash high deposition of desert dust. indicates potential of volcanic ash significant iron source.

in august 2008 kasatochi volcanic eruption in aleutian islands, alaska, deposited ash in nutrient-limited northeast pacific. ash (including iron) resulted in 1 of largest phytoplankton blooms observed in subarctic. fisheries scientists in canada linked increased oceanic productivity volcanic iron subsequent record returns of salmon in fraser river 2 years later