Review Articles in 2013

The Indian Ocean Dipole is a key mode of interannual climate variability influencing much of Asia and Australia. A Review suggests that in response to greenhouse warming, mean conditions of the Indian Ocean will shift toward a positive dipole state, but with no overall shift in the frequency of positive and negative events as defined relative to the mean climate state.

Porphyry ore deposits supply much of the copper, molybdenum, gold and silver used by humans. A review of the main processes that trigger porphyry ore formation suggests that sulphide saturation of the magmas that supply the metals could be the overriding mechanism that helps control the temporal and spatial distribution of the ore deposits.

Methane is an important greenhouse gas, responsible for about 20% of the warming induced by long-lived greenhouse gases since pre-industrial times. A compilation of observations and results from chemical transport, ecosystem and climate chemistry models suggests that a rise in wetland and fossil fuel emissions probably accounts for the renewed increase in global methane levels after 2006.

The Arctic is warming faster than any other region in the world. The resultant large-scale shift in sea ice cover could increase oceanic emissions of dimethylsulphide, a climate-relevant trace gas generated by ice algae and phytoplankton.

Coastal upwelling regimes associated with eastern boundary currents are the most biologically productive ecosystems in the ocean. A suite of human-induced changes could perturb primary production and nutrient cycling in these highly dynamic systems.

The leakage of cold, methane-rich fluids from subsurface reservoirs to the sea floor sustains some of the richest ecosystems on the sea bed. These cold-seep communities consume around two orders of magnitude more oxygen than the surrounding sea floor as a result of the microbial consumption of seep methane.

The flux of carbon out of the ocean surface is not sufficient to meet the energy demands of microbes in the dark ocean. A review of the literature suggests that non-sinking particles and microbes that convert inorganic carbon into organic matter could help to meet this deep-ocean energy demand.

A substantial amount of atmospheric carbon taken up on land is transported laterally from upland terrestrial ecosystems to the ocean. A synthesis of the available literature suggests that human activities have significantly increased soil carbon inputs to inland waters, but have only slightly affected carbon delivery to the open ocean.

Photosynthetic microbes, collectively termed phytoplankton, are responsible for the vast majority of primary production in marine waters. A synthesis of the latest research suggests that two broad nutrient limitation regimes — characterized by nitrogen and iron limitation, respectively — dictate phytoplankton abundance and activity in the global ocean.

Tropical climate and the composition of the global upper atmosphere are affected by the tropical tropopause layer. A synthesis report concludes that transport and mixing in the tropopause region are closely linked with the Asian monsoon and other tropical circulation systems, with possible implications for the impacts of climate change on this important layer.