Climate Change Flashcards

Final Exam and Course Grade

• The final exam will focus on the 4th section of the course.
• The final will not be cumulative, but understanding of fundamentals from prior sections (e.g., sulfur cycling) is expected.
• Course grades will be curved.
  • Example: If 80% is the highest score, an 80% would receive an "A".

Projected Environmental Changes Due to Climate Change

• Sea surface warming.
• Ocean "acidification".
• Salinity changes.
• Increases in stratification and shallower mixed layers.
• Micro- and major nutrient cycling and availability.
• Sea level rise.
• Decrease in sea ice.
• More intense and more frequent extreme weather events.
  • Century storms every 3-10 years.

Effects of Climate Change on Ocean Biology

• Ability to adapt/evolve depends on the time scales of change.
• Current rates of change are unprecedented.

Possible Responses to Climate Change Stressors: Individuals and Populations

• Movement/migration.
  • Phytoplankton blooms in new regions.
  • E. huxleyi in the Bering Sea.
  • Reduction in the range of N2 fixation due to maximum temperature limits.
• Acclimation.
  • Refers to an individual's short-term, reversible physiological adjustments to a new environment.
  • Difficult to acclimate to multiple stressors (e.g., lowered pH and increased temperature).
• Adaptation/evolution.
  • Involves long-term, genetically based changes within a population over multiple generations.
  • Improves ability to thrive in a particular environment.
  • Microbes can evolve rapidly.
  • Example: Oil pollutant resistant genotypes appeared in 30 days in a single-celled alga (Carrera-Martinez et al. 2010).
• Extinction.

Evolution and CO2

• Cell division rates in hours per day for a diatom at 400 and 1000 µatm pCO2 in laboratory growth experiments.
• CO2 levels in top grey panels indicate the level of CO2 in the mesocosm where the lineages evolved.
• CO2 levels indicated on the bottom x-axis indicate CO2 level under which growth was measured in the laboratory.
• Points show cell division rates for individual lineages.
• Cells adapted to 1000 µatm divide faster.

Simultaneous Effects of Climate Change

• Increase in sea surface temperature.
• Adverse effects on microbial community.
  • Community structure modifications.
  • Biogeographic range shifts.
  • Adaptive evolution.
• Alterations in global biogeochemical cycles.

Projected Changes in Global Marine Primary Production

• Many areas predicted to have lower primary production in the future.
• A few areas predicted to have a bit more primary production.
• Figure shows projected climate-driven changes in annual mean net primary production by the end of the twenty-first century (difference between 2090–2099 and 1860–1869 decadal means).

Global Patterns in Ocean Physics and Chemistry

• Jan 2010 atmospheric temperature vs. mean 1950-1980s.
• Mean 1990s pH vs. pre-1700s.
• Rate of global sea level rise 1993-2001.
• Storm duration.
• Ice coverage.

Global Warming vs. Climate Change

• Global Warming: An overall warming of the planet, based on average temperature over the entire surface.
• Climate Change: Changes in global or regional climate characteristics, including temperature, humidity, rainfall, wind, and severe weather events.
• Scientific consensus: Global warming is occurring, and anthropogenic increases in CO_2 and other ‘greenhouse gases’ result in increased atmospheric temperatures, decreased oceanic pH, and many related changes.

Greenhouse Gases

• Gases that trap heat in the atmosphere.
  -The direct radiative effect of a mass of methane is ~72 times stronger than the same mass of carbon dioxide over a 20-year time frame but it is present in much smaller concentrations.

Short Term Changes in [pCO_2]

• Keeling Curve.
  • General increase over time.
  • Annual Cycle.
• pCO_2 on Apr 20, 2025 = 430.5 ppm
• Highest record in this dataset: Apr 2025 = 430.5 ppm

CO_2 Annual Increase

• Rates of CO_2 addition to the atmosphere are increasing. NOAA, SCRIPPS INSTITUTION OF OCEANOGRAPHY, UC San Diego.

Long-Term Time Series

• Measurements at the Mauna Loa Observatory stopped after the 2022 eruption of the Mauna Loa volcano.
• Observatory staff has established limited solar power and restored approximately 33 percent of the measurements.

Long Term Changes

• “Hockey stick chart” (Mann et al. 1999/IPCC 2001).
• 1000 years gives perspective on recent temperature changes.
• 800,000 years of pCO_2 data.

Ice Cores

• Generally from Greenland & Antarctica.
• Vostok ice core: close correlation between temperature and pCO_2.
  • Reconstructed atmospheric CO_2 and air temperature.

Ice Cover

• Ice cover in the Arctic and Antarctic.

Gas Concentrations in Oceans and Atmosphere

• Gas concentrations in the oceans and atmosphere are linked (Dore et al. 2009).
  • Net air-to-sea transfer of carbon.
  • CO_2 dissolves as inorganic C in surface waters.
  • Affects pH.

Ocean Acidification

• CO_2 additions to seawater buffered through the following equation:
• CO2 + H2O + CO3^{2-} \rightleftharpoons 2HCO3^{-}
  • carbon dioxide + water + carbonate ion \rightleftharpoons 2 bicarbonate ions
• Consumption of carbonate ions impedes calcification.

Marine Carbonate System

• The marine carbonate system is the largest carbon pool in the atmosphere, biosphere, and ocean.
• Dissolved CO_2 in ocean occurs primarily in three forms.

Impacts of Ocean Acidification

• There will be winners and losers (From Kroeker et al 2013, in UNEP CBD Technical series #75).
• Impacts on pelagic communities:
  • Calcification -23% (fewer carbonate ions available as pH drops).
  • Growth +17% (more CO_2 in the water for photosynthesis!).
• Impacts on microbes:
  • Non-calcifying phytoplankton may benefit from future OA (e.g., diatoms).
  • Calcifying phytoplankton may have a difficult time producing calcified shells and tests.
  • E.g., Planktonic foraminifera and pteropods - decreased calcification rates under future OA.
  • Mesocosms combining both calcifying and non-calcifying phytoplankton show enhanced primary production under elevated CO_2.
• CaCO_3 shells dissolve in acidified water (Pteropods, Bednarsek et al. 2012).
• Shell corrosion at projected pCO_2 levels in 2100 (~800ppm) (Kerr 2010).

Cost of Ocean Acidification to Marine Calcifiers in the Southern Ocean

• Ocean acidification results from the ocean absorbing CO_2 from the atmosphere.
• In the Southern Ocean, ocean acidification is expected to cause alterations to ecosystem structure and function, carbon export and biogeochemical cycling.

Phytoplankton Response to Warmer Waters

• They grow faster! (to a point).
• They don't all respond the same way!

Thermal Performance

• “Thermal reaction norm”.
• \mu_{max}
• T_{opt}
• T_{min}
• T_{max}

Differences in Species Responses to Temperature

• The SLOPE differs among these important groups.
• Proportional growth change predicted between historical (1950–1970) and future (2080–2100) temperature regimes under the RCP 8.5 climate scenario (Anderson et al. 2021).
• The direct effects of temperature may reshape phytoplankton communities.
• Need to consider which groups export a lot of Carbon.
• Is important to know which phytoplankton are where and what their physiology is.