Title: 226Ra and 228Ra HLY 02-01 Authors: Dr. David Kadko University of Miami RSMAS/MAC 4600 Rickenbacker Causeway Miami, FL 33149 305.361.4721 (phone) 305.361.4689 (fax) dkadko@rsmas.miami.edu Funding Source and Grant Number: National Science Foundatio Office of Polar Programs OPP 0124872 Data Set Overview: The main goal of the (SBI) program is to understand the physical and biological processes within the shelf/slope of the Chukchi and Beaufort Seas that influence the structure and functioning of the Arctic Ocean. This program focuses on understanding exchange and interaction between Arctic shelves and the basin. To this end, our PHASE II program applies an isotopic tracer technique to investigate the rate of exchange between the Arctic shelves and the Arctic Ocean interior. The technique utilizes the measurement of the water column ratio of the naturally occurring radium isotopes 228Ra/226Ra. Because 228Ra (T1/2= 5.77y) is derived through input from shelf sediments, it is an unambiguous marker of water that has been in contact with shelves. Its relative distribution in shelf and basin water is therefore very valuable in assessing the degree of shelf-basin interaction. Temporal Coverage: May 5 - June 15 2004 Physical location: Chukchi and Beaufort Seas in the Western Arctic Ocean Data Collection and Processing: Radium isotopes were extracted upon manganese - coated acrylic fibers through which seawater sampled from niskin bottles flowed. It has been shown that these fibers adsorb radium isotopes efficiently and without fractionation (Moore et al., 1995). In the process, approximately 200 L of seawater were slowly drained through a plastic tube filled with the Mn-fiber. The fibers are subsequently sealed in petrie dishes where, on land, the 228Ra/226Ra activity ratio is determined by measuring the activity of the radium daughters by gamma ray spectrometry (e.g. Michel et al., 1981). The counting system is calibrated with known radioactive sources in a geometry that matches that of the fiber samples. Our laboratory has two low background, high efficiency germanium detectors which allow a throughput of about 200 samples/year. Data Format: Data is provided in Excel and ASCII formats. Data are given in units of dpm/100L (disintegrations per minute per 100 liters of seawater). Uncertainty is the standard deviation due to counting statistics, or of multiple counts (whichever is greater) Data version: Final. March 29, 2004 Data Remarks: NONE References: Michel J., Moore W.S. and King P.T. (1981) ?-Ray spectrometry for determination of radium-228 and radium-226 in natural waters. Anal.chem. 53,1885-1889. Moore W.S., R.M. Key and J.L. Sarmiento (1985) Techniques for precise mapping of 226Ra and 228Ra in the ocean. Journ. Geophy. Res., 90, 6983-6994.