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Ekman transport direction relative to wind

90º to the right in the Northern Hemisphere (NH) and 90º to the left in the Southern Hemisphere (SH)

Why does Ekman transport occur?

Due to the Coriolis Force, which deflects moving objects caused by Earth's rotation

What causes ocean gyres?

Interaction between Ekman Transport and Geostrophic Balance (balance between Coriolis force and pressure gradients)

Most important role of the ocean

To be wet

Definition of an ice age

A period with cold temperatures leading to significant ice sheet expansion across North America and Northwestern Europe

When did ice age cycles occur?

Between 2.7 million years ago and 10,000 years ago

What is the Last Glacial Maximum (LGM)?

The most recent and intense glacial period during the last ice age, occurring around 20,000 years ago

Physical evidence of ice age cycles

Moraines (debris left by glaciers), erratics (large boulders), drumlins, and striations

Ocean sediment evidence for ice age cycles

Oxygen isotopes (O16 and O18) from dead organisms at the bottom of the ocean

Ice core records and ice ages

Oxygen isotopes and air bubbles reveal CO2 levels, which lag behind temperature changes and are affected by external processes

How does O18 ratio relate to ice volume?

More O18 in ocean sediments indicates more ice on land because:

Necessary summer condition for triggering an ice age

Cold summers with less ice melting

Necessary winter condition for triggering an ice age

Warm winters with increased precipitation and ice accumulation

Obliquity's role in ice ages

Changes in Earth's tilt; less tilt reduces solar energy at high latitudes, encouraging ice formation

Precession's role in ice ages

A wobble in Earth's axial rotation that affects seasonal solar radiation, especially in low latitudes

Eccentricity's role in ice ages

Earth's orbit becomes more or less circular, affecting annual mean insolation

Ice

albedo feedback - Ice reflects sunlight, cooling the Earth further

Water vapor feedback

Amplifies warming or cooling based on temperature

CO2 and CH4 feedbacks

Minor compared to other feedbacks but correlated with ice volume

Relative importance of ice

albedo today vs ice ages - Significant during ice ages when ice reached midlatitudes but less important in modern times

Duration of recent ice age cycles

100,000 years: 90,000 years for ice buildup, 10,000 years for rapid warming

Which hemisphere cools more during ice ages?

The Northern Hemisphere, due to larger landmass and ice sheets

Definition of Holocene

Current interglacial period starting 10,000 years ago, characterized by relatively stable and warmer climate

Early to mid

Holocene climate - Greater axial tilt caused warmer summers, stronger monsoons, and increased precipitation in the tropics

Green Sahara during the Holocene

Due to the warmer, wetter climate, the Sahara region was covered in grasslands

Relationship between Holocene and human civilization

Development of agriculture and the rise of civilizations coincide with the stable climate of the Holocene

Definition of Little Ice Age (LIA)

A cooler period from 1600-1800, particularly affecting Europe

Cause of the LIA

Increased volcanic activity, which increased albedo and cooled the surface

Faint Young Sun Paradox solution

Higher greenhouse gas concentrations offset the lower solar output in Earth's early history

Decline in methane (~2.3 billion years ago)

Oxygen from photosynthesis reacted with methane, reducing its concentration

Decline in CO2 (~542 million years ago)

Evolution of multicellular life increased solid carbon storage through shells and biomass

Role of Atlantic formation (~150 million years ago)

Shallow Atlantic prevented shell dissolution and CO2 release, setting the stage for Ice Age cycles

Definition of natural climate variability

Temporary deviations in climate metrics due to internal interactions of Earth's system components

Examples of natural climate variability

ENSO, droughts, North Atlantic Oscillation, year-to-year storm differences

Non

examples - Short-lived anomalies from volcanic eruptions or long-term geologic changes

ENSO's significance

Dominant pattern of year-to-year climate variability, especially affecting tropical and global weather

ENSO frequency

Occurs every 3-7 years

Normal ENSO conditions

Easterly winds push warm water westward, causing upwelling of cool water in the Eastern Pacific

El Niño conditions

Weakening of Easterlies causes warmer conditions in the Eastern Pacific

La Niña conditions

Strengthening of Easterlies causes cooler conditions in the Eastern Pacific

ENSO impacts

Affects global temperature, tropical rainfall, Western U.S. storminess, and extreme weather events

Radiative forcing definition

A change in Earth's energy balance due to natural or human factors, altering the climate system

Positive radiative forcing

More incoming energy leads to warming

Negative radiative forcing

More outgoing energy leads to cooling

Radiative forcing units

Measured in Watts per square meter (W/m²)

Natural climate forcings

Volcanoes increase albedo (cooling); sunspots increase solar insolation (warming)

Primary human forcings

Greenhouse gases (CO2, CH4, N2O), aerosols, and land-use changes

Human sources of CO2

Fossil fuel burning, biomass burning, cement production

Human sources of N2O

Fertilizers, livestock, nylon production

Human sources of CH4

Agriculture (livestock burping), landfills, coal, and natural gas production

IPCC definition

Intergovernmental body summarizing climate science; founded by WMO and UNEP

SSP5

8.5 (high emissions) - Rapid economic growth with high reliance on fossil fuels, limited mitigation

SSP3

7.0 (business as usual) - Fragmented world with uneven development and medium-high emissions

SSP2

4.5 (middle of the road) - Intermediate development pathways with moderate mitigation efforts

SSP1

2.6 (heavy mitigation) - Global sustainability focus, strong mitigation and low emissions

SSP1

1.9 (strongest mitigation) - Ambitious goals to achieve net-zero emissions and limit warming to 1.5°C

Ekman transport direction relative to wind

90º to the right in the Northern Hemisphere (NH) and 90º to the left in the Southern Hemisphere (SH)

Why does Ekman transport occur?

Due to the Coriolis Force, which deflects moving objects caused by Earth's rotation

What causes ocean gyres?

Interaction between Ekman Transport and Geostrophic Balance (balance between Coriolis force and pressure gradients)

Most important role of the ocean

To be wet

Definition of an ice age

A period with cold temperatures leading to significant ice sheet expansion across North America and Northwestern Europe

When did ice age cycles occur?

Between 2.7 million years ago and 10,000 years ago

What is the Last Glacial Maximum (LGM)?

The most recent and intense glacial period during the last ice age, occurring around 20,000 years ago

Physical evidence of ice age cycles

Moraines (debris left by glaciers), erratics (large boulders), drumlins, and striations

Ocean sediment evidence for ice age cycles

Oxygen isotopes (O16 and O18) from dead organisms at the bottom of the ocean

Ice core records and ice ages

Oxygen isotopes and air bubbles reveal CO2 levels, which lag behind temperature changes and are affected by external processes

How does O18 ratio relate to ice volume?

More O18 in ocean sediments indicates more ice on land because:

Necessary summer condition for triggering an ice age

Cold summers with less ice melting

Necessary winter condition for triggering an ice age

Warm winters with increased precipitation and ice accumulation

Obliquity's role in ice ages

Changes in Earth's tilt; less tilt reduces solar energy at high latitudes, encouraging ice formation

Precession's role in ice ages

A wobble in Earth's axial rotation that affects seasonal solar radiation, especially in low latitudes

Eccentricity's role in ice ages

Earth's orbit becomes more or less circular, affecting annual mean insolation

Ice-albedo feedback

Ice reflects sunlight, cooling the Earth further

Water vapor feedback

Amplifies warming or cooling based on temperature

CO2 and CH4 feedbacks

Minor compared to other feedbacks but correlated with ice volume

Relative importance of ice-albedo today vs ice ages

Significant during ice ages when ice reached midlatitudes but less important in modern times

Duration of recent ice age cycles

100,000 years: 90,000 years for ice buildup, 10,000 years for rapid warming

Which hemisphere cools more during ice ages?

The Northern Hemisphere, due to larger landmass and ice sheets

Definition of Holocene

Current interglacial period starting 10,000 years ago, characterized by relatively stable and warmer climate

Early to mid-Holocene climate

Greater axial tilt caused warmer summers, stronger monsoons, and increased precipitation in the tropics

Green Sahara during the Holocene

Due to the warmer, wetter climate, the Sahara region was covered in grasslands

Relationship between Holocene and human civilization

Development of agriculture and the rise of civilizations coincide with the stable climate of the Holocene

Definition of Little Ice Age (LIA)

A cooler period from 1600-1800, particularly affecting Europe

Cause of the LIA

Increased volcanic activity, which increased albedo and cooled the surface

Faint Young Sun Paradox solution

Higher greenhouse gas concentrations offset the lower solar output in Earth's early history

Decline in methane (~2.3 billion years ago)

Oxygen from photosynthesis reacted with methane, reducing its concentration

Decline in CO2 (~542 million years ago)

Evolution of multicellular life increased solid carbon storage through shells and biomass

Role of Atlantic formation (~150 million years ago)

Shallow Atlantic prevented shell dissolution and CO2 release, setting the stage for Ice Age cycles

Definition of natural climate variability

Temporary deviations in climate metrics due to internal interactions of Earth's system components

Examples of natural climate variability

ENSO, droughts, North Atlantic Oscillation, year-to-year storm differences

Non-examples

Short-lived anomalies from volcanic eruptions or long-term geologic changes