F. Große et al.: Looking beyond stratification 
2525 
www.biogeosciences.net/13/2511/2016/ 
Biogeosciences, 13, 2511-2535, 2016 
! „»■**** ** i 
—i , 
."v- " 
r Í 
mean MLD 
Lot. depth 
15.19m 
47.75 m 
( a ) 
;area 
mean volume 
1.85E+09 m 
7.42E+1Ô m 3 
3 
MLD [m] 1 
Region no. 03: 
2002 
Ïfe-Î 
80 
60 
40 
20 
0 
-20 
-40 
-60 
-80 
100 
-120 
«slg-fer-^^ 
i! t. i ik 
mean MLD 
bot. depth 
15.99 m 
47.75 m 
(b) 
area 
mean volume 
1.8SE+08 m 2 
7.3^E+10 m 3 
1- 
MLD |m] 
O 
Öß 
■—60 o 
Sß 
[Region no. 03: 20 101 
•'Sií** 
strat. period: 131/03-03/10 ? 
thIcfcfïëSs:! 7.75 m 
bqt. depth:;47.75 m ! 
area': il. 8 5E+0S m 2 
I volume:; 1.44E+1Ö m 3 i 
■(c) 
- Oxygen cone. 
■ ■ Oxygen sat. cor 
■'Vert, mixing 
■'Adveetion 
- Primary prod. 
Zoopl. respir. 
Pelagic remin. 
Benthic remin. 
■Nitrification 
strat. period: 
11/03-13/09 
thickness: 
bpt. depth: 
7.75 rii ■ 
47.7.5 m I 
1.85E+09 m 2 
1.44E+1Ö m s 
: volume: 
(d) 
“Í ^ “> “i “s 'S 'z 
Hÿ L> -Ö- TÍ? <o 
A 
-80 
-100 
-120 
70 
60 
50 
40 7 
30 o CT 
oo 
20 B 
O 
-10 tus 
-20 
-30 
-40 
Figure 8. Mass balances of simulated CL in region 3 (see Fig. 2) during stratification (grey shaded): (a, b) for the entire volume below the 
MLD (grey dash-dotted; according to Eqs. (1) and 2), (c) and (d) only for the bottom layer for the years 2002 (a, c) and 2010 (b, d). Same 
legend for all panels. Black y axes apply to processes, magenta y axes apply to CL (saturation) concentrations. Values of black y axes in 
(a) and (b) also apply to MLD (unit: m). Changes in CL due to different processes are cumulative. Text boxes list relevant stratification 
parameters, average volume of the analysed water body and bottom depth. Note different y axes for (a), (b) and (c), (d). 
The vertical mixing of CL through the mixed layer 
(MIXo,) adds up to 26.9 gCL m~ 2 in 2002 (1.5-fold of 2010 
value). In late April and late June 2002, two events of en 
hanced mixing cause a rapid gross increase in the CL concen 
trations, in the latter case even resulting in a net increase in 
CL. During August 2002, MIXo, even has a negative effect 
on CL, which coincides with a very shallow MLD of 10m 
(= bottom of first model layer). In 2010, this negative effect 
on CL is even more persistent. The increased positive net ef 
fect of ADVo, and MIXo, in 2002 relates to the stronger 
spatial CL gradients due to the local CL minimum in region 3. 
The daily rates of change in CL (averaged over the strat 
ification period) due to these factors for the different years 
provide a comparable measure of their effect on sub-MLD 
CL, independent of the duration of stratification. The av 
erages of these daily rates for the entire period 2000- 
2012 result in 0.008 ± 0.060gCL m~ 2 d -1 for ADVo, and 
0.153 ±0.042gCLm _2 d _1 for MIXo,. The small positive 
average value and the large SD for ADVo, show that on av 
erage adveetion is only a minor source of CL, however, with 
large year-to-year variability. The average and SD for MIXo, 
show that vertical mixing consistently causes a net increase 
in sub-MLD CL. 
3.4.2 Biological drivers of the sub-thermocline O2 
dynamics 
In contrast to the integrated effect of the physical factors. 
Fig. 8a and b show that the biological processes cause a net 
loss in CL. The only source process for CL is primary produc 
tion (PP; dashed light blue) which causes a gross increase of 
about 61.8 gCLm -2 in 2002 (1.4-fold of 2010 value). Con