Climate Change Impacts on the Marine Environment Ken Ridgway CSIRO Marine and Atmospheric Research Wealth from Oceans National Research Flagship www.csiro.au
Acknowledgements Jeff Dunn, John Church, Katy Hill, Dean Roemmich, Wenju Cai, Ming Feng, Scott Condie
Outline The ocean environment current and eddy field around Australia The drivers of the Australian marine climate Impacts of climate change on the marine environment
Outline The ocean environment current and eddy field around Australia The drivers of the Australian marine climate Impacts of climate change on the marine environment
Major Current Systems Influences from east, west and south
Influence of Boundary Currents Sea surface temperature (SST)
Seasonal Penetration of Current Systems July January
Ocean Connection south of Australia South Indian Gyre Flinders Current EAC Tasman Outflow ACC Continuity of Ocean Properties
Southern Hemisphere Subtropical Super Gyre Three southern gyres connected south of Tasmania and Africa to form Supergyre Results from a linear Sverdrup-Munk Model Tilburg (2000)
Pacific to Indian Ocean 2 pathways Indonesian Throughflow Surface 400-m Tasman Outflow 1000-m
Outline The ocean environment current and eddy field around Australia The drivers of the Australian marine climate Impacts of climate change on the marine environment
The three-headed dog of the Australia climate Indian Ocean Dipole ENSO Cerberus Southern Annular Mode
Forcing by Greenhouse Gases
Climate model features Consist of atmosphere, land surface and biosphere, oceans and polar ice Computed in 30-minute time-steps over a global grid for months or years Adequately simulate observed daily weather and average climate patterns
Models Reproduce Temperature Change
Outline The ocean environment current and eddy field around Australia The drivers of the Australian marine climate Impacts of climate change on the marine environment
Long term Record at Maria Island 60-year time series at Maria Island Seasonal to long-term record of EAC flow Temperature Salinity 18 16 14 12 12 10 10 (a) 35. 35. 6 35. 35. 4 35. 2 35. 2 35.0 35 34. 8 34. 8 34. 6 34. 6 (b) Property 2 1 0 0-1 - 2-2 (c) 1950 1960 1970 1980 1980 1990 1990 2000 2000 1950 1960 1970 1980 1990 2000 1950 1960 1970 1980 1990 2000 te sa 1950 1960 1970 1980 1990 2000 1950 1960 1970 1980 1990 2000 Year
Decadal scale Changes Observed Cold event in mid 1990 s Temperature Salinity 18 16 14 12 10 (a) 35. 6 35. 4 35. 2 35 34. 8 34. 6 (b) 2 Property 1 0-1 -2 (c) 1950 1960 1970 1980 1990 2000 1950 1960 1970 1980 1990 2000 1950 1960 1970 1980 1990 2000 Year
EAC Decadal Variability \ PX34 EAC weakens Strengthens Maria Island Data Cold and warm events evident in PX34 section correlated with EAC transport
Largescale Spatial Pattern of SST Trend 2 0-2 te sa 1950 1960 1970 1980 1990 2000 Trend at Maria 2.28 C/century ~ 3x background value Trend at each gridpoint from SST reconstruction (ERSST)
Observed Gyre Spin-up WOA01 Climatology WOCE Observations show the gyre accelerates by ~ 30% during the past decade (Roemmich et al, 2006). Argo Argo - WOCE Dynamic height (1000/1800 dbar) Change in SLP (contours, mb) and Ekman pumping (colors, m/yr) for the 5-year average 1997/2001 minus 1988/1992, from NCEP/NCAR reanalysis. The pattern reflects an increase in the SAM.
Changes in Gyre Circulation from 1950 s to 1990 s Poleward shift in SH winds cause spin-up of gyre Ozone depletion, SAM and global warming influence (Cai, 2005, 2006) 1950 s 1990 s
Temperature anomaly ( C) 0 0 Salinity anomaly (psu) PX34 Transport Wind stress curl anomaly(*10 8 N/m 2 ) 3 2 1 Total flow through Tasman Sea (Sv) 3-5-yr lag Rossby wave speed @ 34 S Maria decadal changes and trend forced by EAC flow which in turn responds to gyre adjustment to basin scale wind forcing Katy Hill (2006)
EAC extends southward in a climate change experiment Control : Wind driven circulation Climate change: 2070-2100 Latitude of EAC maximum
Mark 3 warming pattern referenced to global mean temperature Greatest warming rate in the SH Cai et al., CLIVAR EXCHANGE, 2004
SST Trend ( C/century) Mk3 2070 Surface Temperature ERSST data (1944-2005) 2 0-2 Long-term Station Maria Island te sa 1950 1960 1970 1980 1990 2000 Global Climate Model Forecast
Warming trend in the Indian Ocean SST trend (1960-1999) SST at Rottnest Is Station Leeuwin Current follows basin trend
Southward shift of the subtropical gyre
IMOS a new marine observing system
Future Research is needed Support for existing and new observations Improved climate models Reanalyze past changes in ocean heat content and salinity distribution - compare with model simulations of 20C climate Explore attribution of changes (GHG, aerosols, natural variability) Downscaling of global models to regional scales Continued involvement in international programs
Present Future?
Thank you www.csiro.au
Changes in Marine Living Resources indicate Long term changes Invasion of Sea Urchins native to NSW coast causing loss of Kelp forests in off eastern Tasmania (N. Bax) Changing composition of Phytoplankton blooms off Tasmania increased tropical species and red tides (S. Blackburn) Rock lobster catch and distribution correlated with regional SST changes around Tasman Sea (Harris et al 1988) In last decade 34 fish species have exhibited major distributional changes: either newly established south of Bass strait, or show significant range extensions. (P. Last)