Direct observations of the Indonesian Throughflow in Timor and Ombai Straits 2011-2015

Susan Anne Wijffels, Woods Hole Oceanographic Institution, Woods Hole, MA, United States, Beatriz Pena-Molino, CSIRO Hobart, Centre for Southern Hemisphere Ocean Research, Hobart, TAS, Australia, Bernadette Sloyan, CSIRO Oceans and Atmosphere, Hobart, TAS, Australia and Craig Raymond Steinberg, Australian Institute of Marine Science, Townsville, QLD, Australia
As part of Australia’s Integrated Marine Observing System, 4 tall moorings were deployed from May 2011 to October 2015 across the largest exist straits of the Indonesian Throughflow: Ombai Strait and Timor Passage. These are believed to carry 83% of the Indonesian Throughflow transport as it exits into the Indian Ocean. The Timor moorings are sited at the eastern end of Timor Strait while the Ombai site is identical to that used in the 2004-2006 INSTANT campaign, providing a seven year record there. Here we describe the variability captured in these direct velocity observations and compare it with those observed during 2004-2006 from INSTANT. The flow structure in eastern Timor Passage is distinct from that downstream at the western INSTANT sites, with the core found close to the southern shelf break. In both passages we find a large (> 30%) decrease in transport from June 2013 to October 2015. We will explore the drivers of this change. Lastly we will describe a new international field campaign, MINTIE, aiming to capture the transport divergence and internal water mass variability in the Indonesian Seas.