PC34B-0637
Variability in the Nordic Sea stratification during MIS 11: Any relevance to AMOC? BENOIT THIBODEAU ,HENNING A BAUCH ADINA PAYTAN , 4 5 THOMAS F PEDERSEN & ANDREAS SCHMITTNER 1
1 2
2
3
The University of Hong Kong, Dept. of Earth Sciences & Swire Institute of Marine Science (
[email protected])
Alfred Wegener Institute, 3UC-Santa Cruz, Institute of Marine Sciences, 3University of Victoria, 4Oregon State University
1. The Nordic Seas were characterized by a cold, fresh and thick mixed layer during Marine Isotope Stage 11 TI
MIS 1
3.0
MIS 5e
3a. Hypothesis 1: AMOC intensity lower or similar compared to MIS1?
TV
MIS 11
T II
3. Any relevance to AMOC?
δ18O (‰)
3.5 4.0 2
5.0
3
0
5
4
Warmer water
60 2
40 20
50
10 8 6 4 2 0
150
0
0
5
10
NPs habitat
15
120
130
380
400
420
0
440
Age (ka) TI
High productivity and almost complete nutrient consumption
Very High δ15N Low NPs
Low productivity Deep mixing layer
Low δ15N
MIS 5e
T II
High produc- Low productivity and high nutrient tivity consumption Deep mixing layer High δ15N Medium NPs
Low δ15N
MIS 11
High productivity and mediumnutrient consumption
Medium δ15N Very High NPs
Vazquez-Riveiro et al., 2013, EPSL
3b. Hypothesis 2: AMOC intensity increased compared to MIS1?
TV
Low productivity Deep mixing layer
Photic zone
Water Depth
100 50
Thibodeau et al., 2017, EPSL
Kandiano et al., 2016, GRL
50
100
MIS 1
Thibodeau et al., 2017, EPSL
0
0
IRD (grains/10ccm) > 500 µm
CaCO3(%)
20
80
4
MAR CaCO3 (g cm-2 ky-1)
40
6
G. uvula (%)
60
+ Nitrate utilization
NPs (%)
Thibodeau et al., 2017, EPSL
T. quinqueloba (%)
δ15N (‰)
8
δ18O NPs (‰)
4.5
Low δ15N
Thibodeau et al., 2017, EPSL
2. The modeled impact of freshwater release in the North Atlantic on the N-dynamic in the Nordic Seas decreas
e in N-u
tilization
ΔSSS and δ18O stack ΔSSS (M23414-M23060)
δ15N of nitrate
Impact of hosing on δ15N of nitrate in Nordic Seas
100 years hosing control
1000 years hosing Year and month of simulation
1
4.0
0
3.8
-1
3.6
-2
3.4
-3
3.2
-4 390
δ18O [‰] 400
410
Age [ka BP]
1.0
20
Flow (Sv) No change in N-source Year and month of simulation
0 -10 -20
deeper mixed-layer
-30 390 Kandiano et al., 2016, GRL
Kandiano et al., 2017, Sci. Rep.
0.8 0.6
δ13C-benthic forams Overturning Inflow 400
410
Age [ka BP]
0.4 420
430
δ13C [‰]
δ15N of nitrate
10
deeper mixed-layer
430
Model (STELLA)
100 years hosing impact on mixed-layer depth in the Nordic Seas
100% size mixed-layer
420
