Annual report 2005-06.indd - Antarctic Climate and Ecosystems ...

sea-level riseSLR-02: Estimates of oceanthermal expansionProject leaderJohn Church, CSIROProject staffN White, S O’Farrell, CSIRO; N Bindoff, UTAS/CMARProject AimIncreased confidence in our understanding ofchanges in sea level during the 20 th centuryis dependent on more accurate estimates ofobserved 20 th century thermal expansion and theconfirmation that climate models are realisticallysimulating observations. This confirmationwill result in reduced uncertainty of futureprojections of thermal expansion.Key achievements in 2005-06• Showed that volcanic eruptions have asignificant impact on ocean heat contentand steric sea level (Nature 2005). Post-1960 volcanic eruptions masked part of theacceleration that would otherwise have beenpresent.• Nearing completion of a new observationalestimate of ocean thermal expansion for the1990s and the period 1960 to 2000.• Demonstrated that modelled and observedsea level display similar signatures ofatmospheric, oceanic and coupled variabilityin both control and transient simulations. Thelongest modes of variability are driven by theocean thermohaline circulation, with periodsof 20-70 years.SLR-03: Ice sheet and glaciercontributions to sea-level riseProject leaderIan Allison, Australian Antarctic Division (AAD)Project staffN Young, R Warner, AAD; J Hunter, ACE; NAdams, BOM; S O’Farrell, CMARProject AimThe balance between accumulation of ice andsnow on ice sheets and the discharge of waterto the sea from them determines the influenceof the ice sheets on global sea level. Thisproject will deliver more robust estimates ofsnow and ice accumulation on the Antarctic andGreenland continents during the 20 th and 21 stcenturies. Modelling of these ice sheets will alsodeliver estimates of longer-term contributionsto changes in sea level from ice discharge ormelt water from Greenland and Antarctic IceSheets. We will draw on international efforts toestimate contributions to changes in sea levelfrom glacier melting as well as from ice sheets.These improved projections will, in turn, guideAustralian decision-makers in the formulation ofpolicy and management strategies to respond tosea level change induced by climate change.Key achievements in 2005-06• Detected a small positive mass budget overthe upper part of Law Dome using a 40-yearrecord from gravity surveys. This surface riseis consistent with a snow accumulation rateincrease since the 1960s.• Detected episodic rift propagation fromanalysis of passive seismic observationsand GPS measurements, and assessed riftpropagation on the Amery Ice Shelf bysatellite image analysis.• Showed a decrease in extent of theShackleton and West Ice Shelves from acentury of historical records.• Applied our ice shelf model to the MertzGlacier tongue and explored changes in flowand ice thickness arising from projectedincreased basal melting expected underprojected climate change.• Advanced our reassessment of East Antarcticmass budget using ANARE historical fielddata, and presented results at WCRP Sealevelworkshop.• Undertook the first survey of icebergnumbers and size characteristics round theentire Antarctic coastal seas using satelliteimagery.Antarctic Climate & Ecosystems CRC - Annual Report 2005-06 45