Lecture 33: Tides of Change (1&2) Final

What is the distinction between weather and climate?

Weather: Refers to the short-term atmospheric conditions in a specific location, changing minute-to-minute, hour-to-hour, day-to-day (e.g., today's temperature, rain, or wind).

Climate: Refers to the long-term average of weather conditions and extremes in a region, typically averaged over a 30-year period (e.g., the expected average temperature and rainfall for a month or season).

What is the relationship between ocean temperature and land temperature (the graph on the second slide)? What does this indicate about the future of ocean temperatures?

The ocean acts as a massive heat sink, absorbing over 90% of the excess heat trapped by greenhouse gases, which causes land and atmospheric temperatures to increase less dramatically than they otherwise would.

Future Indication: Due to this massive heat absorption, the ocean's thermal inertia means it will continue to warm and release that stored heat back to the atmosphere for centuries, even if atmospheric warming stops. This indicates a commitment to long-term warming and associated effects like sea level rise.

Why is there interest in the ocean's role as a carbon sink?

There is significant interest in the ocean's role as a carbon sink because the ocean absorbs roughly 25-33% of anthropogenic carbon dioxide from the atmosphere. This action significantly mitigates the rate of atmospheric warming and climate change.

How is inorganic carbon form related to water pH?

When CO2 from the atmosphere dissolves into seawater, it reacts with water to form carbonic acid. Carbonic acid quickly dissociates, releasing Hydrogen ions into the water. The increase in the concentration of these H+ ions increases the water's acidity and thus lowers the water's pH.

Explain the process of ocean acidification (i.e., what is the acid? Where is it coming from?).

Carbonic acid is the primary acid formed. The acid comes from the reaction of water with excess atmospheric CO2, which is primarily derived from the burning of fossil fuels (coal, oil, and natural gas).

How does ocean acidification impact organisms?

The excess of H+ ions reduces the availability of carbonate ions which are the building blocks of calcium carbonate.

Organisms like corals, oysters, clams, pteropods (sea snails), and certain plankton struggle to build and maintain their shells and skeletons, leading to slower growth, weaker structures, and potential dissolution.

What is the correlation between warmer ocean temperatures and hypoxia?

Reduced Solubility and Increased Stratification

Why do we discuss the hydrologic cycle in terms of "climate change" instead of "global warming"?

Because the problem is far broader than just temperature increase.

"Global warming" describes the rise in average global surface temperature.

"Climate change" is the more comprehensive term, encompassing the wide range of effects resulting from the warming, including changes in the hydrologic cycle (e.g., increased evaporation, more intense rainfall in some areas, and prolonged droughts in others), shifting weather patterns, and rising sea levels.

What is the correlation between warmer ocean temperatures and extreme weather (e.g., hurricanes)?

Fueling Storms, Rapid Intensification, and Wetter Storms

What two processes are causing sea level rise?

Thermal Expansion and Melting of Land-Based Ice

What is coastal submersion? Is this expected to affect Texas?

The permanent or semi-permanent inundation of coastal land due to relative sea level rise (global sea level rise combined with local land subsidence). Yes

What is freshwater intrusion? Is this expected to affect Texas?

The contamination of coastal freshwater aquifers by saltwater due to rising sea levels or excessive groundwater pumping that reduces freshwater pressure. Yes

What are the social implications of the ocean processes listed above?

Economic Disruption, Human Displacement, Health, and Food Security

How will sea level rise affect shallow marine habitats?

Sea level rise causes the inundation and loss of shallow marine habitats such as salt marshes, tidal wetlands, and mangrove forests. This loss is exacerbated by "coastal squeeze," where these habitats cannot migrate inland because of human development (seawalls, roads, etc.) that block their movement.

What is the Atlantic Meridional Overturning Circulation (AMOC)? Where is it located? What role does it play in thermohaline circulation?

A key part of the thermohaline circulation (or "global conveyor belt").

Extends throughout the Atlantic Ocean, particularly from the subpolar North Atlantic to the Southern Ocean.

It transports warm, salty surface water northward from the tropics. In the North Atlantic, the water cools, becomes denser, and sinks, driving a deep, southward flow of cold water, thereby distributing heat globally and regulating climate, particularly in Europe.

What is the current observed trend in the strength of the AMOC?

A significant slowdown/weakening in strength over the past few decades, attributed to surface warming and an influx of freshwater from melting Greenland ice (which makes the surface water less salty and thus less dense, hindering sinking).

What are possible consequences of the AMOC weakening or collapsing?

Regional cooling of Northern Europe, rising sea levels along the North American Atlantic coast, and shifts in global precipitation patterns.

What is the Antarctic Circumpolar Current (SMOC)? Where is it located? What role does it play in thermohaline circulation?

The other major component of the global thermohaline circulation.

Southern Ocean, surrounding Antarctica.

It is crucial for driving the entire global circulation system by forming the cold, dense bottom water masses that eventually spread northward into the world's deep ocean basins.

What is the current observed trends of the SMOC?

The SMOC is believed to be weakening or even reversing its deep water circulation in some areas due to changing water temperatures and densities.

What are possible consequences of these changes? (SMOC)

Disruption of global ocean currents (including feedback to the AMOC), and altered regulation of the planet's heat and carbon distribution.

What is the current state of ice and climate in the Arctic?

Amplified Warming and Ice Loss

What is the current state of ice and climate in the Antarctic?

Overall Mass Loss, Melting, and Complexity

Define Shifting Baseline Syndrome.

Shifting Baseline Syndrome (SBS) is a psychological and sociological phenomenon where each generation accepts the degraded state of the natural environment they grew up with as the new "normal" or "healthy" baseline, without personal knowledge, memory, or experience of its historical, richer condition.

How does shifting baseline syndrome complicate human attitudes and policies toward climate and biodiversity?

Increases Tolerance, Lower Expectation, Inappropriate Baselines.