6
Chapter 3:
Figure 3.1: Simplified schematic of the water mass circulation in the North Atlantic (adapted from
Garcia-Ibanez et al., 2015) superimposed with the GEOVIDE cruise track (thick grey line) and stations
(colored diamonds). Surface currents are represented ..........................................................................96
Figure 3.2: Chlorophyll-a (Chl-a) concentrations in mg.m-3 (closed symbols) and total phaeopigment
over Chl-a ratios (TPhaeo/Chl-a; open symbols) in the upper 200 m. ................................................ 104
Figure 3.3: Main phytoplankton size groups and chloropigments (from the GEOVIDE database). a)
Relative abundance of microphytoplankton (black line, circles), nanophytoplankton (dark green line,
squares), picophytoplankton (light green line, triangles). b) Relative abundance of Fucoxanthin (black),
19’-HF (light grey), Zeaxanthin (dark grey), and peridinin (white) pigments ....................................... 105
Figure 3.4: Particulate
234
Th activities for the small size fraction (SSF; 1-53 µm; open diamonds) and
for the large size fraction (LSF; >53 µm; open triangles); Total
234
Th (closed blue circles) and
238
U (thick
grey vertical line); all activities expressed in dpm.L
-1
. The horizontal black line is the Eq depth (depth
where
234
Th returns to equilibrium with
238
U) used for estimating the export fluxes, and the horizontal
green line is the calculated PPZ depth (primary production zone). Error bars are hidden by the symbols
............................................................................................................................................................. 108
Figure 3.5:
234
Th flux attenuation between Eq and 400 m (in dpm.m
-2
.d
-1
). Negative values indicate an
attenuation of the
234
Th flux between Eq and 400 m while positive values denote an increase of the
234
Th
flux between both depths. The error bars are calculated using the error propagation laws. .............. 111
Figure 3.6: POC:
234
Th ratios (µmol.dpm
-1
) in the SSF (open symbols) and LSF (closed symbols). The
Eq depth (depth where
234
Th is back to equilibrium with
238
U) is indicated with the grey line except for
Stations 26, 44 and 69 where the Eq depths are represented by green, pink and purple lines,
respectively. The thin black line represents the power law fits (POC:
234
Th=a×Z-b) of each province or
basin. ................................................................................................................................................... 114
Figure 3.7: POC:
234
Th ratios (µmol.dpm
-1
) between the small size fraction (SSF) and large size fraction
(LSF) at Eq (left) and at 400 m (right). The diagonal black line represents the 1:1 ratio. For the readability
of the figure, the error bars of Station 1 are not indicated (errors: LSF=17.2 µmol.dpm
-1
and SSF=13.8
µmol.dpm
-1
). ......................................................................................................................................... 115
Figure 3.8: Export fluxes of particulate organic carbon (POC), calcium carbonate (CaCO
3
), biogenic
silica (BSi) and particulate aluminum (pAl) at Eq (solid fill) and at 400 m (dashed), from the Iberian
Margin (Station 1) to the Newfoundland Margin (Station 77). ............................................................. 118
Figure 3.9: Upper 20 m integrated satellite-derived Chl-a concentrations (black line) from
http://giovanni.sci.gsfc.nasa.gov/giovanni/. The pink line represents the sampling period during
GEOVIDE and the black stars represent the Chl-a concentration measured in-situ. ......................... 124
Figure 3.10: a) POC export fluxes at Eq versus daily primary production (PP) and b) POC export fluxes
at Eq versus POC export fluxes at 400 m. For the readability of the figure, the error bars for the POC
export fluxes of Station 1 are not indicated (error at Eq=22 mmol.m
-2
.d
-1
and at 400 m=10 mmol.m
-2
.d
-1
)
and Station 26 (error at Eq=6.7 mmol.m
-2
.d
-1
and at 400 m=7.3 mmol.m
-2
.d
-1
). ................................. 130
Chapter 4:
Figure 4.1: Satellite Chlorophyll-a concentrations (MODIS Aqua from http://oceancolor.gsfc.nasa.gov),
in mg.m-3 during the GEOVIDE cruise (May and June 2014). Stations are indicated by the diamonds.
Colored diamonds indicate the approximate time of sampling. ........................................................... 147
Figure 4.2: a) Schematic of the circulation features, adapted from Garcia-Ibanez et al., 2015. b) Salinity
along the GEOVIDE section, and associated water masses: LSW: Labrador Seawater; ISOW: Iceland
Scotland Overflow Water; IcSPMW: Iceland Subpolar Mode Water; SAIW: Sub Arctic Intermediate
Water; NACW: North Atlantic Central Waters; MW: Mediterranean Water; DSOW: Danmark Strait Water;
NEADW: North East Atlantic Deep Water. Stations in bold correspond to stations where detailed vertical
Niskin profiles were collected. ............................................................................................................. 149
Figure 4.3: Barite particles observed by FE-SEM at a) Station 38 (300 m); b) Station 44 (700 m); c and
d) Station 69 (600 m). The white arrows indicate the position of barite crystals. ................................ 155
Figure 4.4: Section of the particulate biogenic barium (Baxs) in pmol.L
-1
determined in samples collected
with the Go-Flo bottles. Niskin detailed vertical profiles were determined at stations in bold. ............ 157
Figure 4.5: Individual profiles of Baxs concentrations (in pmol.L
-1
) determined using Niskin bottles from
GEOVIDE (squares) and GEOSECS (circles) cruises. ....................................................................... 158
Figure 4.6: Total bacterial abundance (cells.µL
-1
) measured by flow cytometry (J. Laroche, J. Ratten
and R. Barkhouse, personal communication). .................................................................................... 160
Figure 4.7: Regression of the 100-500 m integrated total bacterial abundance (events.µL
-1
) versus the
100-500 m DWA Baxs values (pmol.L-1). ........................................................................................... 161
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