Scientists and engineers with AOML's Physical Oceanography Division have successfully designed, built, and tested a new antenna system that dramatically increases data transmission reliability while drastically reducing operating costs. The new Iridium-based transmission system has no restrictions on data format or size, allowing data from various ocean and land-based observation platforms to be transmitted more securely and at a fraction of the cost as the older Inmarsat‐C platform. Since its completion, PhOD researchers have adopted the system on a number of expendable bathythermograph (XBT) transects, as well as simultaneously tested and implemented it on other AOML observing systems. Use of the new Iridium system has resulted in a 95 percent reduction in the average transmission cost for an XBT profile, with an estimated savings to NOAA of more than $200,000 annually.
A fall rate experiment was conducted aboard the UNOLS R/V Endeavor, which sailed from Puerto Rico on February 15, 2015 in support of AOML's Western Boundary Times Series Program. During the cruise, over 100 XBTs were deployed to assess biases in temperature profiles based on XBT launch height.
AOML reached an important milestone in October: the deployment of 8000 expendable bathythermograph (XBT) probes each year for the past two consecutive fiscal years. XBTs are launched globally from ships of opportunity and measure ocean temperature as they descend through the water. AOML’s XBT network includes the maintenance of 15 XBT transects in partnership with institutions from Argentina, Australia, Brazil, France, Italy, Japan, South Africa, and the U.S. In addition to the collection and distribution of temperature profiles, AOML’s XBT network also provides support to the National Weather Service for the collection of marine meteorological observations, as well as to the Global Drifter and Argo programs. During the last two fiscal years, 93 drifters and 67 Argo floats were deployed by XBT riders on cargo ships in data sparse remote regions without much ship traffic.
A study on the Antarctic Circumpolar Current (ACC) by researchers with AOML’s Physical Oceanography Division and the Marine Research Institute of the University of Cape Town has been published online by the Journal of Geophysical Research. In this study, the authors used data from the AX25 repeat expendable bathythermograph (XBT) transect (which runs from South Africa to Antarctica) with h ydrographic and satellite observations to assess the link b etween local wind forcing mechanisms, the variability in upper ocean temperatures, and the dynamics of the different fronts in the ACC region south of South Africa. The authors report a mechanism by which local winds alter the structure of the ACC flow in the region. These changes in the local ACC structure were found to be due to anomalies of opposite signs in the transport of the Subantarctic Front (SAF) and Antarctic Polar Front (APF) caused by latitudinal shifts of the westerlies. Full reference can be found here: Domingues et al. (2014)
The XBT/CTD pairs dataset (Version 1), used to calculate the historical XBT fall rate and temperature corrections presented in Cowley et al (2013), has been made publicly availble through the following DOI permanent link: http://dx.doi.org/10.4225/08/52AE99A4663B1. Each dataset contains the scientifically quality controlled version and the original data, when available. The publication of this dataset provides new ground for additional research on the XBT biases, in support of improvements on the XBT technology.
In a recent paper (Abraham et al. 2013), scientists assessed the evolution of ocean temperature measurement systems focusing on the development and accuracy of two critical devices in use today (expendable bathythermographs and CTDs – conductivity-temperature-depth instruments used on Argo floats). A detailed discussion of the accuracy of these devices and a projection of the future of ocean temperature measurements are provided. The accuracy of ocean temperature measurements is discussed in detail in the context of ocean heat content, Earth’s energy imbalance, and thermosteric sea level rise. The latest data for thermal expansion sea-level rise are included and analyzed.
With the collaboration of the Servicio de Hidrografia Naval (Argentinean Coast Guard) an AX18 cruise from Argentina to South Africa was conducted during the month of August, 2013. This was the 35th realization of this transect that has been continuously occupied since 2002. The XBT data collected along this transect is used to monitor the meridional mass and heat transport in the upper 800m along 30°S. XBT are mostly deployed from cargo vessels with the help of shipping companies that voluntarily participate in the Ship Of Opportunity Program. The recent AX18 cruise was carried out on board the MOL's Onix Ace.