Kadko Metadata ---TITLE: 224Ra and 228Th HLY 02-01 ---AUTHOR: David Kadko -Complete mailing address, telephone/facsimile Nos., web pages and E-mail address of PI Dr. David Kadko University of Miami RSMAS/MAC 4600 Rickenbacker Causeway Miami, FL 33149 tel; 305 361 4721 fax 305 361 4689 dkadko@rsmas.miami.edu ---FUNDING SOURCE AND GRANT NUMBER: National Science Foundation Office of Polar Programs OPP 0124872 ---DATA SET OVERVIEW: -Introduction or abstract 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 activities of the naturally occurring isotopes 224Ra and 228Th. Because 224Ra (T1/2= 3.64d) is derived through input from shelf sediments, it's excess over the parent 228Th is an unambiguous marker of water that has been in very recent contact with shelves. Its relative distribution in shelf and basin water is therefore very valuable in assessing the degree of shelf-basin interaction. -Time period covered by the data May 5 -June 15 2002 -Physical location of the measurement or platform (latitude/longitude/elevation) Chukchi and Beaufort Seas in the Western Arctic Ocean -Data source, if applicable (e.g. for operational data include agency) NA -Any World Wide Web address references (i.e. additional documentation such as Project WWW site) NA ---INSTRUMENT DESCRIPTION: NA ---DATA COLLECTION and PROCESSING: Radium and thorium isotopes were extracted upon manganese - coated acrylic fibers through which seawater sampled from niskin bottles flowed. It has been shown that these fibers adsorb these 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. After drainage, the fiber-filled tube was placed in a stripping line and 224Ra was determined by counting its daughter 220Rn (T1/2 = 55.6 sec). Within a closed circulation loop, the 220Rn is stripped directly into a ZnS coated scintillation cell/photomultiplier counting system (Moore and Arnold, 1996). The efficiency of the system is determined by a 228Th (parent of 224Ra) standard solution. This procedure is replicated for most samples over a period of several weeks to determine the 228Th activity of the sample. For some samples, the second count was not performed until many weeks after the cruise such that the 228Th activity had to be corrected for ingrowth from its 228Ra parent. ---DATA FORMAT: -Data file structure, format and file naming conventions (column delimited ASCII) -List of parameters with units, sampling intervals, frequency, range 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 number and date Final. April 20, 2004 ---DATA REMARKS: NONE ---REFERENCES: 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. Moore W.S. and Arnold R. (1996) Measurement of 223Ra and 224Ra in coastal waters using a delayed coincidence counter. Journ. Geophy. Res., 101, 1321-1329.