Coastal Forcing Coasts are the ribbons that form the interface between regions dominated by terrestrial and marine surface processes, respectively, and are the most dynamic (rapidly changing) of the Earth's landscapes Shaped greatly by storm wind energy transferred to waves Wave energy is dissipated and converted into work that involves the movement of sediment and/or the erosion of rock. The coast is the bottom boundary condition for the terrestrial landscape, which influences river gradients and cliff heights. Oceans are the "final" sink for terrestrial sediment and water.

Relative Sea Level Rise Fundamental variable that determines whether a coast is sandy or rocky. RSL=SL-R Both eustatic sea level (SL) and vertical crust motion (R) can be positive or negative, and if their particular combination makes RSL<0, crustal rock is exposed and can be attacked by waves in the nearshore. If RSL>0, a veneer (often times many meters thick) of sediment blankets the bedrock and allows sedimentary landforms to be shaped by wave-generated nearshore currents.

Sea Level during the Pleistocene Over the past few million years, the major cause of eustatic sea level change is the waxing and waning of global ice volume. The shape of the ocean basins makes it possible to use the following relationship between sea level and ocean volume: Oxygen isotope data from benthic forams in marine sediment cores provide the bulk of the Pleistocene record, and this has been calibrated with oxygen isotopes of air bubbles trapped in ice cores, whose ice has been deposited over the Last Glacial Maximum (LGM).

Sea Level during the Holocene Fast growing coral that live within 5 m of sea level on stable shelves provide a record of sea level history since the LGM. They can be dated with U/Th methods to provide the time information. Sea level rise accelerated from the LGM to about 14ka, when a dramatic melting event (MWP 1a) occurred. During that time, SL rose 25 meters in 500 years. Calculation of MWP 1a discharge = approx. 6 Amazon Rivers being turned on for that interval.

Sea Level Rise During the Last Century A: Effect from glacial melt: Changes in global ice volume, i.e. glacier sizes, are extremely difficult to quantify. Interestingly, it appears that small Alaskan glaciers constitute the bulk of global small glacier contribution to sea level rise. B: Effect from thermal expansion of water (steric effect): some caveats here: 1. The coefficient of thermal expansion, a, is temperature dependent. 2. The thickness of the column of warmed water, H, is only the well-mixed layer, whose thickness varies with latitude. 3. The temperature of the well-mixed layer, upon which the coefficient of thermal expansion depends, also has a latitudinal variability.

Markers of Rock Uplift Rocky coast markers - Marine Terraces - very useful, because they are known to originally be horizontal. Can be dated to reveal long term uplift rates.

Markers of Rock Uplift

Wave Anatomy

Wave Energy Density Across Frequency

Wave Refraction

Longshore Current

Storm Surge