Much of the emphasis in recent years in climate geoengineering research has focused on the solar radiation management strategies of injecting sulfur dioxide particles, or other substances into the stratosphere to increase albedo, or to seek to brighten maritime clouds to effectuate the same objective. However a new study by Ivana Cvijanovic, Ken Caldeira and Douglas G MacMartin in the journal Environmental Research Letters seeks to focus on an approach which has received very little scrutiny to date, the potential impacts of ocean albedo alteration. While the lion’s share of limited research that has occurred in the context of terrestrial surface albedo alteration, several researchers have proposed ocean-based approaches, including hydrosol (microbubble) injection and stabilization and the floating of granular materials. Cvaijanovic et al. in this study sought to enhance understanding of the climatic impacts of ocean surface albedo alteration in the Arctic, using a model-based scenario that they emphasize is an idealized one that may not reflect how such approaches might ultimately be deployed. The study employed the National Center for Atmospheric Research’ Community
Earth System Model. Altered ocean albedo simulations were branched from year 100 of the fully coupled 4xCO2 simulation and run for 50 years.
Among the findings of the study are the following:
- In the simulation with albedo alterations (0.9) imposed over 70°–90°N September sea ice area was 3.17 ± 0.16 million km2 or , ~40% of pre-industrial 1xCO2 extent, compared to only ~3% of pre-industrial extent in the scenario of carbon dioxide levels quadruple pre-industrial levels with no albedo modifications. In the simulation, annual mean sea ice area in the region equaled 74% of its preindustrial value, compared to 51% in the 4xCO2 simulation with no albedo modifications. Prescribing albedo at a lower level, e.g. 0.7 or 0.8 resulted in a September sea ice returning to 28% of its pre-industrial levels. Albedo modification impacts in other latitudes in the Arctic, such as 65°–90°N or 80°–90°N, were less efficient in terms of recovery of sea ice;
- Model-imposed surface ocean albedo in the Arctic did not have substantial impact on planetary albedo values;
- Imposed albedo modifications and sea ice recovery leads to modest decreases in surface temperatures, with the largest annual mean cooling achieved in alb65–90N, of ~2.5 K. Mid-latitude temperature decreases are also recorded, but more modest;
- Arctic sea ice recovery would likely lead to drier conditions over northern portions of the United States, and wetter conditions over southern parts of the United U.S. West Coast;
- While not constituting a global panacea for climate change, ocean albedo modification could be used to ameliorate regional impacts, or even on a smaller scale to effectuate sea ice restoration in individual bays or estuaries;
- While not specified, the study concluded that ocean albedo modification could have substantial impacts on Arctic marine biospheres.