P17N Comparison (WOCE vs Japanese reoccupation)

Japanese data downloaded from WHPO on 6/16/04 and imported into local database. Since the U.S. occupation of this line did not 
extend as far south as the Japanese, data from the U.S. P17C section was included. Comparison thus extends from 30N to ~54N. 
The quality of the new Japanese data set is excellent. 

Details:
Stations used: WOCE P17C (17-26) +  P17N (28-119); Japan P17N (all except X01)

Alkalinity: Lamb et al. (DSR II, 49(1-3), 21-58, 2002) suggested that the WOCE P17N alkalinity measurements were systematically 
high by 12 umol/kg. This adjustment was applied to the WOCE P17N alkalinity data prior to comparison to the Japanese data. 
The  plot P17nDeepAlkComp.pdf implies that the adjustment suggested by Lamb et al may have been a bit too much. Visual inspection 
of this plot implies that a correction of -10 may have been more accurate.

TCO2: Lamb et al. (DSR II, 49(1-3), 21-58, 2002) suggested that the WOCE P17N TCO2 measurements were systematically high by 4 umol/kg. 
This adjustment was applied to the WOCE P17N TCO2 data prior to comparison to the Japanese data. This adjustment is sufficiently small 
that careful quantitative comparison would be required to determine if it was appropriate. At sigma theta = 26.5 there is a significant 
TCO2 increase of 10 to 30 umol/kg from 1993 to 2001 extending from 32.5N to 52.5N. This increase is coincident with an AOU increase.

AOU: There is an AOU increase (WOCE-Japan<0) from 1993 to 2001 centered at sigma theta 26.5 and extending from 32N to 52N of 20 to 
30 umol/kg.

Nutrients: Both nitrate and phosphate show a small increase from 1993 too 2001 at 26.5. This change is not as persistent as the AOU 
and TCO2 change. For both sections the nitrate/phosphate ranges from 0 at the surface to ~14 at depth. There is no significant change 
in the ratio between the two sections except near the surface. The NO and PO differences are almost identical. Both show significant 
increase from 1993 to 2001 in near surface waters between 37N and 47N. PO shows a small decrease at sigma theta 26.5, but the latitude 
extent is not as great as for the tracers mentioned above. The NO decrease at that level is a bit shallower and even less convincing.

Plots: The upper portion of each plot shows a contoured section using the  WOCE data and the stations listed above in sigma theta 
space (24-27.1). The heavy black line in the upper portion of this plot is the winter time mean potential density for the ocean surface 
taken from Levitus along the cruise track.

The lower portion of each plot shows the change in the property between the two occupations. In each case, the difference is WOCE-Japan or 1993-2001.

Plots were prepared for: depth, salinity, oxygen, AOU, nitrate, phosphate, NO, PO, alkalinity, tco2 and C14. In each plot red indicates 
a decrease from 1993 to 2001 and blue indicates an increase.