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18 April 2007: Prepared for OCB data system by Cyndy Chandler, OCB DMO (WHOI).
These data are from the filters from in-situ pumps (LVP)
operated by Ken Buesseler's group and used on both the Melville and Polar Star. These data have also been published in:
K. O. Buesseler, J. E. Andrews, S. Pike, M. A. Charette, L. E. Goldson, M. A. Brzezinski, and V. P. Lance, 2005.
"Particle export during the Southern Ocean Iron Experiment (SOFeX)".
Limnol. Oceanogr., 50(1). American Society of Limnology and Oceanography, Inc. pp.311-327.
(download PDF). The sampling and analysis methodology is also described in that publication.
Original Excel file received via email from PI: copy of original Excel file
The 13C and 15N measurements were done by people in Mark Altabet's lab at UMass Dartmouth. Some notes from David Timothy (School for Marine Science and Technology University of Massachusetts, Dartmouth, MA) accompanied the original Excel data file:
"These results are NOT blank subtracted! I don't think I included columns for POC and PN per filter, but you'll see these can be calculated easily (volumes filtered are on the spreadsheet). I won't be surprised if after blank subtraction there are negative values; some of the > 54um samples had very low POM."
DMO processing notes
Melville sampling dates: At some point the sampling dates for the Melville data were put into MS Excel on a Mac system. MS Excel on a Mac uses a different date system from Windows. On a Mac, serial day 1 = Jan 1, 1904 and on Windows, Excel serial day 1 = Jan 1, 1900, and 1900 is an exception to the 4 year leap year rule because it is divisible by 100. When the Excel data file was first ingested into the OCB database, the dates were all off by 4 years and 1 day. However, the actual Excel serial day of 37280.32292 that was entered in the original file is equivalent to Jan 24 2002 07:45:00 - notice the correct year and the time agrees with the event log GMT. The data were copied from the original file and pasted into a new MS Windows Excel file prior to ingestion into the database. This resulted in new sampling dates that matched the cruise's event log except as noted in the next section.
Also, after the date offset (Mac vs. Windows Excel) issue was resolved, the original datafile reported data from station 4 at 08:45 GMT on 25-Jan (according to the MV event log, station 4 was reportedly occupied on 29-Jan, but station 2 had a pump cast on 25-Jan at 08:43). Also, several rows of data were reported from station ? on 29-Jan. The DMO determined this to be station 4. Station 34 data were reported for 11-Feb, but according to the cruise event log, this station was actually done on 12-Feb. The LVP data file was adjusted accordingly to agree with the Melville cruise event log.
The 'patch_loc' field: The SOFeX 'patch_loc' field is usually one of four abbreviation codes indicating the sampling location relative to the 'iron fertilized patches'; N indicates North Patch, S = South Patch, and whether the location is within or outside the patch area or on the edge of the patch. For the Polar Star cruise, it appears that only the relative in/out information was recorded. There were two fertilized patches, one north and one south of the Antarctic Polar Front Zone (APFZ near 61°S) along 170°W. All of the Polar Star sampling events for which patch_loc is recorded were conducted south of 61°S, implying the south patch.
PI notes
The Buesseler lab "large volume pumps" used on the Melville and Polar Star were of similar design. These casts and data are also reported elsewhere in the OCB database. MULVFS, multiple unit large volume filtration system, another sampling device was only used on the Melville. The LVP's yield about 200-500L per sample, while MULVFS yield on order of 2000L or more. Also, MULVFS casts tend to go deeper, to 1000m, where as LVP samples concentrated on the upper 100-200m.
Contact: Ken Buesseler (WHOI)
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