Chemical Oceanography Flashcards
(85 cards)
1
Q
P:N:C:O2
A
1:16:106:153
2
Q
Nitrate
A
NO3 ^-
3
Q
Phosphate
A
PO4 ^ 3-
4
Q
ocean circulation
A
~1000yrs
5
Q
least reactive major ion
A
Cl-
6
Q
main barrier to ocean mixing
A
density difference (hence 2 box model)
7
Q
Ammonia
A
NH4+
8
Q
Average mix layer
A
~70m
9
Q
Anoxic waters have
A
higher burial (recall fish farming)
10
Q
Largest inputs and outputs
A
mixing and particle flux»_space; river input, burial
11
Q
(–) AOU
A
supersaturation
12
Q
Nitrite
A
NO2-
13
Q
In a CaCO3 dominant system
A
surface has decreased Alk, decreased [CO3 2-] pH lower fCO2 higher atm CO2 higher
14
Q
NH4 comes from
A
respiration product
15
Q
what happens to NH4 in surface
A
converted to NO2, NO3 (only in aerobic/oxic zone)
16
Q
local surface max in NH4
A
lag in the conversion from
respiration –– NH4+ –– NO2- –– NO3-
17
Q
Nitrification
A
NH4 + O2 –– NO2- –– NO3-
18
Q
Nitrogen Fixation
A
N2 ––– NH4+
N2 gas from the atmosphere
requires high Fe
19
Q
expected NH4+ profile
A
low [ ] in surface water - possible small max from respiration
major increase is after o-a boundary
20
Q
expected NO3- profile
A
[low/0] right at surface (productivity)
increases throughout surface layer, fairly high max ~1000m (respiration)
anoxic - decreases back to 0 toward o-a boundary
open ocean - remains ~ stable with depth
21
Q
Expected NO2- profile
A
similar to NO3- but much smaller peak
small peak in oxygen layer from nitrification processes
22
Q
high N2
A
denitrification
23
Q
Conservative ions
A
only affected by evaporation and precipitation
no big fluctuations with depth
[ion] : seawater S remains ~constant
Mg, Na, Ca, Cl-
24
Q
Gases
A
affected by T, S, P, f, reactivity
increase with depth (lower T), except O2
25
Bioactive elements
affected by primary production, respiration, remineralization
P, N, Fe, O2
26
Trace metals
Very low concentrations
| Mg, Fe, Co, Ni, Cu, Zn, Cd
27
Oxygen profile without biology
controlled by T like other gases
| increase with depth
28
Oxygen along thermohaline
depleted
| successive losses from respiration
29
AOU
```
[O2]equil – [O2]meas
Apparent Oxygen Utilization
amount respired
oxygen deficit due to respiration
~ opposite to oxygen curve
```
30
typical O2 profile
minimum above 1000m (respiration)
| increase after 1000m (horizontal advection from O2 rich high latitude (cold) waters)
31
Ventilation impact on O2, AOU
larger ventilation (age, older)
lower O2
higher AOU
32
OUR
Oxygen Utilization Rate
mean respiration rate in the water parcel since it left the surface
AOU / Age
high at surface, decrease with depth
33
AOU profile
low at surface
max at O2 min (~500-1000m)
decrease with depth
34
Oxygen minimum occurs
medium age
| medium respiration
35
Carbonate weathering reactions
CaCO3 + CO2 + H2O –– Ca2+ + 2HCO3-
| 2HCO3- + Ca2+ –– CaCO3 + CO2 + H2O
36
low [surface nutrient] affects on fCO2
low [surface nut.] = low fCO2
| high P flux –– low [nut.] –– low C (by RKR) –– low DIC –– low CO2 –– low fCO2
37
high [surface nutrients], fCO2
high DIC = high fCO2
38
Phosphate characteristics
enriched along thermohaline
bioactive, typical bioactive curve
high in S ocean (HNLC)
controlled by photosynthesis and respiration
39
DIP_preformed
```
Preformed = Total – Respired
(DIP_T) – (r_P:O2 x O2_respired)
(DIP_T) – (r_P:O2 x AOU)
Preformed phosphate
portion of P advected to deep irrespective of respiration
```
40
DIP respired
= AOU x (P/O2)
| i.e. r_P:O2 x AOU
41
Phosphate, Nitrate curves
low at surface (productivity)
increase to a max at ~1000m
decrease with further depth, then ~stable in deep waters with no more respiration occurring
42
Nitrate characteristics
Bioactive, typical bioactive curve
extra processes not seen in phosphate
controlled by photosynthesis, respiration (dominantly)
43
DIN_preformed
= DIN_T – (r_N:02 x AOU)
44
Nitrogen cycle in the surface
NO3 – NH4 –> (photosyn.) Org N
OrgN – NH4 (respiration)
Org N particle flux out of surface
45
nitrogen cycle in the deep
P flux -- Org N to the deep
Org N ––(respiration) NH4 ––(nitrif.) NO3
even deeper, anoxic waters
NO3 / Org N –– N2 (denitrification)
46
N*
DIN – 16DIP
| how does [N] differ from the expected P:N ratio?
47
+ N*
N is greater than 16P
| Nitrogen fixation likely occurring (adding N)
48
– N*
N is less than 16P
Denitrification likely occurring, removing N
**must be low O2 waters
49
typical North Atlantic N*
N* +++
| high Fe input which is a requirement for N2 fixation
50
N* Eastern Equatorial Pacific, Arabian Sea
N* –––
| low oxygen zones
51
Preformed nutrients helpful for
separating water masses
52
Denitrification dependent on
O2 only
| independent of [N,P]
53
AABW
HNLC - high preformed nutrient, low chlorophyl
Fe limited
low CaCO3 precipitation -- high Alk
extremely cold (hence, dense)
54
Atlantic characteristics
N = deep water formation, extremely Saline
~2X S of N Pacific (gulf evaporation)
Generally higher N:P than P
High Fe - Sahara
multiple water sources - AABW, AAIW
harder to see DIC, Alk changes along thermohaline b/c of water mass intrusions
55
AAIW
warmer, less dense than AABW, NADW
| spreads out at ~1000m
56
Alkalinity =
[HCO3-] + 2[CO3 ^2-] + [B(OH) ^4-] - [H+]
95% of seawater alk =
[HCO3-] + 2[CO3 ^2-]
57
Alkalinity characteristics
measurable, accurate, not affected by T, P, k (gas exchange)
main effects from CaCO3 precipitation/dissolution
more soluble at depth (P, 'easier' to be small ions)
primarily affected by biology
58
AOU down isopycnal
increases (respiration)
59
[P] down isopycnal
increased (respired)
60
O2 down isopycnal
decreased (used up in respiration)
61
∆Alk from 1mol CaCO3 dissolution
increased 2mol
62
Alkalinity profiles
Atlantic- roughly constant with depth, S Atl is higher
Antarctic - roughly constant
Pacific, Indian - increases with depth (thermoh.)
63
Pacific characteristics
higher DIP, DIN, DIC, Alk than Atl (more productivity, ventilation)
Deep P_pre ~uniform, 1 water mass
lower [CO3 ^2-], pH
higher fCO2
64
DIC =
[CO2] + [H2CO3] + [HCO3-] + [CO3 ^2-]
65
Bicarbonate system
CO2atmos ⇌ CO2ocean ⇌ H2CO3 ⇌ HCO3- ⇌ CO3^2-
66
pH =
-log[H+]
67
fCO2 =
[CO2] / K
68
estimating change in carbonate
∆Alk - ∆DIC ≈ ∆[CO3 ^2-]
69
increase in DIC, constant Alk
decrease in CO3 ^2-
decrease in pH
increase in fCO2
70
salinity normalized DIC
= (DIC / S) * 35
71
Increased Alk, constant DIC
```
bigger ∆Alk – ∆DIC
higher [CO3 ^2-]
higher pH
lower fCO2
less atmospheric CO2
```
72
Biologic pump
particle flux
| relating biological processes, [nutrient], DIC, Alk
73
P:N:DIC:Alk
dependent on OM:CaCO3, using 3.5
| 1:16:136:44
74
∆Alk from 1mol Organic Matter respiration
decrease 16/106mol
| decrease 0.15mol
75
∆DIC from 1mol CaCO3 dissolution
increase 1mol
76
O2 profile Atlantic vs. Pacific
Pac- much lower concentration at minimum (higher productivity)
deeper, longer O2 minimum
77
pH changes with constant DIC, varying Alk
increase Alk = increase pH
| non linear
78
∆DIC from 1mol OM respiration
1mol increase
79
CO3 ^2- changes with constant DIC, varying Alk
increase Alk = increase CO3 2-
| ~linear
80
change in fCO2 with varying Alk, DIC constant
increase Alk = decrease fCO2
| non-linear
81
AOU profiles, Atlantic vs. Pacific
Pac. - deeper, longer, higher max, correlates w/ O2 profile
| higher productivity
82
pH changes with varying DIC, Alk constant
increase DIC = decrease pH
Alk - DIC is smaller
non linear
83
CO3 2- change with varying DIC, alk constant
Increased DIC = decreased CO3 2-
84
fCO2 change with varying DIC, alk constant
increased DIC = increased fCO2
| non-linear
85
Seasonality affects on nutrients
N, P surface concentrations highest in winter, lowest in summer
minimum lags spring phytoplankton blooms
