Multi-decadal Ocean Change

Southeast Australian waters have experienced a multi-decadal warming over recent decades at a rate of between three and four times the global average (Holbrook and Bindoff 1997; Ridgway 2007) – the global average warming rate being about 0.5-0.6oC century-1. Recent work has shown that over the past 30 years the poleward transport of water within EAC eddies has increased significantly (especially from 2005 onwards, Cetina Heredia et al 2014). In addition while the EAC separation point has only moved ~60km poleward, the EAC is separating at the southern extent of its separation range more often (Cetina Heredia et al 2014).

At multi-decadal scales, research into changes in ocean warming, the hydrological cycle and carbon budgets in the oceans s around NSW are some of the topics addressed in the NSW-IMOS science and implementation plan.

The following high-level science questions will guide the NSW-IMOS observing strategy in this area:

Ocean Heat Content:

  • How is the heat transport of the EAC changing, including the offshore recirculation and eddy transport south?
  • How do the offshore heat transport changes of the EAC affect transport by the coastal currents?
  • Can a distinct EAC undercurrent be detected? If so, what is its contribution to the heat transport and how does it vary?

Global Ocean Circulation:

  • What are the mass and heat transports contributions of the Tasman Outflow?

Global hydrological cycle:

  • How are NSW river outflows changing? What are the effects of these changes on salinity patterns?

Global carbon budget:

  • What is the carbon inventory for the coastal waters off NSW and how is it changing on decadal timescales?
    • What are the key biological and physical processes involved in air-sea CO2 exchange in the coastal waters off NSW and how sensitive are they to climate change?
    • How are CO2 fluxes over the continental shelf off NSW evolving and how are the fluxes on the shelf related to the Tasman Sea and the EAC?