Which phytoplankton groups typically have N:P ratios higher/lower than the redfield ratio?
Higher: Diatoms and Dinoflagelates
Lower: Cyanobacteria and Green algae
(????????)
Define the term nitrate deficit (N*). Which are the main biological processes leading to positive and negative N values?
N* = NO3 -16PO4 + 2.9mmol/m3
At a perfect Redfield Ratio N* = 0. If N* < 0 it indicates that Nitrate concentartions exceed the level that is needed for optimal growth. If N* > 0 it indicates that Nitrate concentrations are below the optimal level of phytoplankton growth.
The 2.9mmol/m3 account for a global offset under the assumptoin that N:P values are stable at 16:1 globally
The subtropical North Atlantic is characterzed by comparatively high N:P ratios in inorganic nutrients (called N:P anomaly). What is the reason for this?
The reason for the N:P anomaly is the high Fe input from saharian dust storms, facilitating N2-fixation at high rates leading to a higher N:P ratio.
List the three groups of planktonic organisms mainly responsible for calcification in the ocean. Which of them produces calcite, whch aragonite?
Coccolithophores -> calcite
Foraminifera -> calcite
Pteropods -> aragonite
Explain the terms carbonate saturation depth and carbonate compensation depth (CCD). Which one is deeper?
CSD: depth where Omega = 1
CCD: depth where all CaCO3 is in solution -> no CaCO3 in sediments (this on eis deeper)
Which ocean (Atlantic or Pacifc) has lower carbonate saturation states? What is the reason for that?
Pacific, because pCO2 is higher due to proceeded respiration in the THC (later in the OCB)
The present ocean is warming, acidifying and losing oxygen. Give two examples each for positive and negatve biogeochemical feedbacks to these changes.
List the three chemical species of the marine CO2 system in order of increasing concentration
HCO3-
CO32-
CO2
How does the seawater temperature influence the solubility of CO2 (K0), the dissociatoin constants of carbonc acid (K1, K2) and the Revelle factor?
K0: decreases with increasing temperature
K1: increases with increasing temperature
K2: increases with increasing temperature
Revelle: decreases with increasing temperature
What are the four measurable parameters of the marine CO2 system (provide the definition equatiion for each
TA -> [HCO3-] + 2[CO32-] + [B(OH)4-] + [OH-] + … (everytthing after this is below 0.2% of contribution)
DIC -> [CO2] + [HCO3-] + [CO32-]
pCO2 -> [CO2]
pH -> -log[H+]
If you wanted to increase the pCO2 of seawater experimentally, which chemical would you add to the seawater if you wanted to (1) increase DIC at constant TA, (2) increase TA at constant DIC, and (3) increase DIC and TA by the same amount?
1) CO2
2) NaOH
3) Na2CO3 and NaHCO3
In which natural surface water would DIC (at equilibrium) increase the most under an atmospheric CO2 increase from 280ppmv to 400ppmv: (1) tropical Pacific, (2) polar North Atlantic, or (3) Amazon river?
Highest increase would be found in the tropical Pacific as CO32- is the dominant driver for CO2 buffering as it is higher at higher temperatures. For a gven atmospheric increase tthe corresponding DIC change in tropical waters is nearly twice as high as in polar waters.
Which physiochemical law is needed to understand the functioning of the physical carbon pump (solubility pump)? This pump was presumably in steady state in pre-industrial times. Why does this pump drive a net uptake of CO2 in the present ocean?
-> Henry’s Law of solubility
At constant pCO2 in the atmosphere over long time periods the physical C-pump would eventually reach steady state as the C-budget is not changing. After the industrial revolution atmospheric pCO2 increased leading to an increased uptake of CO2 in the ocean that which is exported into the deep ocean by the physical C-pump.
Which of the following regions show (1) a summer maximum and (2) a summer minimum in the seasonal cycle of pCO2 in the surface ocean: subtropical gyre, subpolar gyre?
A summer maximum is found in the subtropical gyre while a summer minimum is found in the subpolar gyre:
subtropical gyre: all year round low nutrient concentratioins -> during summer increased solar radiation and warmer temperaures lead to higher primary production -> decrease in pCO2 in the summer months -> summer maximum of pCO2 uptake
subpolar gyre: generally colder temperatures but more mixing during winter months -> mixing/upwelling introduces nutrients -> higher primary production and CO2 uptake during winter months -> summer minimum of pCO2 uptake
The annual cycle of sea surface temperature and net biological productivity influence pCO2 in a counteractive way. Explain why that is. How would the two drivers (temperature and net biological productiviy) affect oxygen?
SST: higher temperatures lead to lower solubility of CO2 in seawater -> CO2 is released into the atmosphere
Productivity: referes to the balance between photosynthesis and respiration -> During periods of high photosynthesis pCO2 in SW and atmosphere decreases
Oxygen:
Warmer SST has the same effect on O2 as on CO2
With higher photosynthetiic rates O2 increases in SW and atmosphere while it is decreased by strong respiration periods
The effects of temperature and biological productivity on O2 and CO2 can vary depending on photosynthesis and respiration
What is the present magnitude of human-induced CO2 emissioins (in Gt CO2/yr)? At this rate, how many years would it take until the remaining allowable CO2 emissions consistent with the 1.5°C warming goal of the Paris Agreement would be reached?
36-37 Gt/yr
There are two different categories of climate intervention technologies. What distinguishes them?
Carbon Dioxide Removal (CDR):
Solar Radiation Management (SRM):
Which mechanisms for enhanced CO2 removal in the ocean are considered? List at least 4
Artificial Upwelling
Ocean Alkalinity Enhancement
Iron Fertilization
Blue Carbon Ecosystems (Mangroves, Seagrass, Sargassum)
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