These are the notes taken during the lectures of Marine Sciences III week 1 to week 4. The course is taught at Utrecht University. It therefore includes the first lecture 'Carbon cycle, climate and ocean change' to the last lecture of week 4 'Plankton and plastic; ocean pollution'.
marine sciences III
LECTURE 1 – WEEK 1: introduction + carbon cycle, climate and ocean change
APPY SLUIJS
INTRODUCTION ○ biosphere has taken up 11 Gt of CO2 → net mass of the
biosphere is growing
● marine sciences II: oceans of the future ○ past decade atmospheric rise per year; 19 Gt of CO2
● major marine sciences themes ○ dissolved inorganic carbon pool is the largest reservoir
○ physical oceanography
○ chemical oceanography
○ biological oceanography
○ analogues of change; paleoceanography
● deadlines literature case studies
○ rationale and questions 14/11, 20:00
○ summary #1 28/11, 20:00
○ summary #2 16/11, 20:00
○ feedback presentation 09/12, 20:00
● since 1965 the atmospheric [CO2] went up
LEARNING GOALS
○ not linear, but a slight rise (exponential)
○ Northern Hemisphere contains the majority of the world’s
● understand how major groups of organisms respond to
land mass → during spring and summer (April-September),
○ single stressors (warming, acidification, anoxia)
extensive vegetative growth occurs; plants absorb large
○ multiple stressors
amounts of CO2 for photosynthesis, which reduces
● understand the response on ecosystem level
atmospheric CO2 levels → in fall and winter (October-
● understand how the system as a whole changed during past
March) decomposition and respiration release CO2 back
analogous changes
into the atmosphere, leading to an increase in
○ get a sense on the time scales involved
atmospheric CO2 levels
GRADES
● summaries (specific for 3 editors) 15%
○ structure, writing in English
● presentation 25%
○ content (presentation, progress reports)
○ presentation (structure, technique)
● exam 60%
MODERN PERTURBATION OF THE CARBON CYCLE
● sources of CO2; annual CO2 emissions
○ increased usage fossil fuel → total annual amount of CO2
● Global Carbon Project
emitted per year has been rising since 60s
○ mission: assist the international science community to
○ there was a drop in the fossil fuel demand in 2020/21 due
establish a common, mutually agreed knowledge base to
to covid crisis → lower CO2 emissions
support policy debate and action to slow the rate of
○ deforestation is stable at about 5 Gt of CO2 per year
greenhouse gas production
○ China is a major emitter contributor
● units
⥽ smallest contributors are EU and India
○ data is shown in billion tonnes CO2 (GtCO2)
⥽ USA has the biggest emitter per capita (person)
○ 1 gigatonne (Gt) = 1 billion tonnes = 1×1015 g = 1 petagram
○ in the last 3 decades there has been an uncoupling of the
(Pg)
amount of money people make and the total CO2
○ 1 kg carbon = 3.664 kg CO2
emissions; increase of wealth doesn't come at the cost of
○ 1 GtC = 3.664 billion tonnes CO2 = 3.664 GtCO2
extra CO2 emissions
● carbon fluxes
○ land-use change is also called deforestation
1
, marine sciences III
LECTURE 1 – WEEK 1: introduction + carbon cycle, climate and ocean change
APPY SLUIJS
● sources of CO2; fossil carbon sourcing
○ annual fossil CO2 emissions in de EU is declining
○ renewable energy grows exponentially, but growth in
fossil energy consumption is faster → ratio still increases
● there are 2 high peaks of airborne CO2 fraction of total
emissions due to El Niño → large part of the tropical Pacific is
stratified → no upwelling → ocean remains warm → ocean
can’t take up a lot of CO2 → CO2 stays in the atmosphere
● contributions of sources and sinks
○ over the past century, land has taken up ~ the same
amount of CO2 as there has been emitted due to
forestation → total amount of biomass on land hasn’t
changed when calculated on a net basis
● balance of sources and sinks ● anthropogenic carbon in the oceans
○ over the past decades there has been a linear sink into the ○ pre-industrial pCO2 ~ 280 ppmv
ocean, atmosphere and biosphere ○ actual (2023 av) pCO2 ~ 419 ppmv
○ worst case scenario: with higher emissions, the ○ no-ocean world pCO2 ~ 470 ppmv
atmosphere would have to take up more CO2, because the (~1/3 of anthr. C in ocean)
ocean and land would be saturated ○ there is a concentration of carbon uptake in the North-
○ process models suggest that increasing atmospheric CO2 Atlantic Ocean
drives the land and ocean sinks while climate change ○ Why does anthropogenic C end up in deeper waters?
reduces the carbon sinks; the climate effect is largest in ⥽ downwelling: formation of deep ocean waters
tropical and semi-arid land ecosystems through density based circulation ← surface ocean
○ globally during the 2013–2022 decade, climate change becomes so dense that it will sink
reduced the land sink by ~20% and the ocean sink by ~7% ● What happens with CO2 in the ocean?
○ CO2 reacts with water to form carbonic acid which
dissociates into a proton and bicarbonate
○ H+ is party used by carbonate to create bicarbonate
○ an increase in bicarbonate results in more H+ in seawater
→ decrease in pH (ocean acidification)
○ increase in pH → decrease in DIC
2
, marine sciences III
LECTURE 1 – WEEK 1: introduction + carbon cycle, climate and ocean change
APPY SLUIJS
1) solubility pump (solubility of gasses increases at lower T);
⅓ of gradient
2) biological pump (biology); ⅔ of gradient
● North Sea; nutrient availability is more important than ● marine organic matter cycle
atmospheric CO2 rise ○ GPP (gross primary production): total rate of carbon
○ pH of the North Sea is primarily a function of nutrient fixation/oxygen release by phytoplankton
availability (primary production; how much CO2 is taken ○ GPP is partly used for respiration (RA) by phytoplankton,
up by the biosphere) the other part is net PP (NPP)
● projections of future pH of the ocean ○ organic matter is consumed by heterotrophs for growth
○ time series of the percentage of total uncertainty ascribed and respiration (RH); remaining OM is new and available
to internal variability (orange), model uncertainty (blue) for export (NEP, new export production)
and scenario uncertainty (green) in projections of global ○ NPP (net primary production) is most relevant for photic
annual mean changes zone food web functioning, while the export production is
○ short time scale; uncertainty in modeling future pH relevant for the biological pump and fueling deep-sea and
○ longer time scale (beyond decades); largest uncertainty is benthic food webs
the emission scenario
○ the amount of CO2 we are going to emit over the coming
decades is going to determinate the uncertainty of future
pH of the ocean
● organic carbon pump
○ net annual NPP: 50 Pg C (1 Pg = 1 Gt = 1015 g), 40 Pg is
respired in the euphotic zone
○ 10 Pg is exported to the ocean interior, of which 8 Pg is
respired in the dark ocean; 2 Pg arrives at seafloor
● surface ocean and deep ocean C gradient
○ in sediments, 90% of the organic carbon delivered is
○ surface ocean is in equilibrium with the atmosphere (a lot
degraded; only 0.2 Pg C yr− is eventually buried
of O2 and less CO2); O2 is supplied to the deep water layers
(transferred to the geosphere)
though ocean circulation
3
, marine sciences III
LECTURE 1 – WEEK 1: introduction + carbon cycle, climate and ocean change
APPY SLUIJS
⥽ decrease because of warming and stratification
(physics)
○ long-term fate of anthropogenic carbon depends on
physics, chemistry and biology
● limitations on better future projections
○ many changes at same time: T, CO2, O2, nutrients,
biodiversity crisis
○ response at species level can be studied, but more difficult
at ecosystem/earth-system level
○ species, sometimes even strains, differ in response
○ evolution and adaptation
○ e-ratio = export production / NPP
⥽ temperature determines the degree to which NPP
organic matter is exported
⥽ magnitude of NPP is important; higher NPP → higher
e-ratio
○ high NPP is usually associated with high [chlorophyll] (an
indicator of plankton biomass)
● geological record of ocean acidification
○ ocean acidification stimulates primary production and
export → CO2 sink
○ ocean acidification limits calcite production → less CO2
production
○ implementing these ocean acidification effects on
biological processes in global model to test potential
effect on global carbon cycle
● oceanic CO2 uptake in future
○ oceans take up about 25-30% now
○ ocean CO2 uptake in future
⥽ increase because of CO2 stimulated growth of
phytoplankton and/or less calcification (biology)
⥽ decrease because of decline in buffer capacity
(chemistry) of the ocean ← ocean becomes more acid
← ocean takes up CO2
4
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