2015 Week 5 questions answered

Week 5 has thrown up a bumper crop of questions so here goes with some answers:

1) If the Himalayan glaciers melt, what effect will that have on SE Asian rivers and reservoirs? Are there any mitigation measures?

As the glaciers are melting it will increase river flow, especially during the summer, once they have melted it will decrease river flow, and that will be particularly obvious in the dry (no monsoon) season, affecting e.g. irrigated agriculture. Aside from mitigating overall climate change, another option is to reduce soot emissions (mostly from biomass burning in wood stoves in India) as soot deposition on the glaciers is darkening them and contributing to the melt.

2) What caused the above normal melting of Greenland in 2012?

There was an unusual ‘blocking’ high pressure weather system that stayed in position on Greenland, with blue skies allowing temperature to build up and melt right across the ice sheet surface – check out the NSIDC report.

3) Will marine organisms be able to adapt in time given the rapid acidification of the oceans?

It probably depends on the organism – microbes can adapt fast, but e.g. long-lived animals with shells adapt much slower. If corals are suddenly placed in a high-CO2 experimental environment they can really struggle, but given decades to adapt they may cope better – we’ll have to wait and see to find out.

4) What are the effects of acidification on marine plants and fish?

Again it depends on the organism. Marine ‘plants’ means cyanobacteria and algae including macro-algae (seaweeds, kelp…). Some algae make their shells out of calcium carbonate, so they are potentially in trouble. Many others have different types of shell (or none at all), so they may get a relative advantage. For fish, the effects of elevated CO2 could include making it slightly harder for them to precipitate carbonates, which is something they do in their guts to regulate their salt balance.

5) Are there any ‘geoengineering’ methods that could be used to reduce the acidity of the oceans?

Yes, potentially – it has been suggested that lime or calcium carbonate could be deliberately added to the ocean (in powdered form) in order to reduce surface water acidification. The problem is you have to calculate how much CO2 is emitted in mining the lime/carbonates, crushing it, and transporting it out into the ocean on boats. L. D. Danny Harvey has done some calculations on this which show that overall it could still be overall ‘carbon negative’ as well as tackling ocean acidification directly.

6) In the past, acidity has supposedly reached higher levels. What were these levels, when did it occur and what impact did it have on marine organisms?

Care is required in thinking about this. The ocean is extremely well buffered, so the only way to lower pH dramatically is to add CO2 very rapidly. There are a few candidate events in Earth history where a natural release of CO2 has acidified the ocean – for example when a magma intrusion torched a massive volume of fossil fuels – but these events are few and far between. A well characterised one is 55 million years ago at the Paleocene-Eocene Thermal Maximum. It caused an extinction event, but not nearly as severe as some earlier extinction events where ocean de-oxygenation appears to have been a more potent killer.

7) Will scientists be able to maintain ‘seed bank’ equivalents of threatened marine organisms?

This is a good idea. We already do this to some extent in aquaria around the world – but generally for the ‘charismatic mega fauna’ (i.e. animals).

8) Would increasing acidity lead to greater dissolving of carbonate rocks? Thus reducing the acidification effect?

Yes, well done to whoever asked this question – dissolving carbonate rocks adds alkalinity to the ocean (2 moles of alkalinity for each mole of carbon added). This is exactly what happened at the aforementioned Paleocene-Eocene Thermal Maximum, and it is what is starting to happen under human-induced ocean acidification. The carbonate ‘rocks’ include ocean sediments themselves as well as harder rocks exposed on land – the chemistry is the same – its just the pH is already much lower in rainwater.

Hope this helps!

Professor Tim

Leave a Reply