Ocean and Climate An Introduction Program in Climate Change Summer Institute Friday Harbor Labs September 2008 Dennis L. Hartmann Atmospheric Sciences University of Washington

Ocean and Climate An Introduction Role in Earth’s Evolution Role in Climate Change - Past & Future Impact of Ocean Change - e.g. sea level. Impact of Human Activities and Climate Change on the Ocean - e.g. acidification.

Basic Properties The Ocean is Dark - low albedo The Ocean is Wet - Cools by Evaporation The Ocean is a fluid with mass/heat capacity –Can store and release energy quickly (or slowly) –Can move energy around –Can store and release trace chemicals (e.g.CO2) The Ocean can freeze, in which case it is a bright solid and energy transfer by phase transition is less important (sublimation).

The Ocean is Dark

Ice-Albedo Feedback As the Earth warms, ice melts in high latitudes and altitudes This lowers the albedo of Earth and leads to further warming. Ice reflects more solar radiation than other surfaces

Ice-Albedo Feedback As the Earth warms, ice melts in high latitudes and altitudes This lowers the albedo of Earth and leads to further warming. Ice reflects more solar radiation than other surfaces

The Ocean is Wet

The Ocean Stores Energy

The Surface Energy Balance

Ocean Heat Capacity Instant Response GCM Response Manabe & Stouffer 2007

Heat Capacity/Transport IPCC AR4

North Atlantic Circulation

Atlantic MOC IPCC AR4

ENSO

El Niño La Niña

ENSO El Niño

ENSO Stratosphere El Niño - Garfinkel & Hartmann 2007

ENSO State and Variability IPCC AR4

Tropical SST and Clouds Distribution of tropical SST is hypothesized to have strong effect on clouds and the energy balance. For example, marine boundary layer clouds have strong leverage on the radiation balance and depend on the strength of the trade winds and SST gradients.

Marine Boundary Layer Clouds Form above lower SST.

Marine Boundary Layer Clouds %

Cover a significant fraction of the Earth’s Surface Have a large effect on Earth’s Energy Budget Cloud Forcing of the Energy Balance Wm

Ocean a Source/Sink of radiatively active gases and aerosols. Carbon uptake/release –Glacial/Interglacial –Anthropogenic Carbon uptake - 50% DMS production - Sulfate Aerosols/CCN Sea Salt Aerosols

The atmospheric concentration of CO 2 and CH 4 in 2005 exceeds by far the natural range of the last 650,000 years CO 2 CH 4

Ocean Acidification IPCC AR4

Aragonite Saturation

Ocean Acidity

The Ocean Freezes, or not - Sea Ice Freezing of seawater an important driver of thermohaline circulation. Sea Ice + Snow = insulation Large albedo increase. Polar amplification and seasonal dependence of polar warming - largest polar warming in winter.

Disappearing Sea Ice

Ocean and Clouds