Sea-Level ChangeSea-Level Change

Sea-levels are predicted to rise by 1m this century (by 2100).

Why?

Sea-Level Change Key Sea-Level Change Key TermsTerms

EustaticEustatic – global-scale sea level change – global-scale sea level change caused by a change in the volume of caused by a change in the volume of water in the ocean storewater in the ocean store

IsostaticIsostatic – local-scale sea level change – local-scale sea level change caused by a change in the level of the land caused by a change in the level of the land relative to the level of the sea.relative to the level of the sea.

EmergenceEmergence – the impact of a relative – the impact of a relative FALL in sea level FALL in sea level (Marine Regression)(Marine Regression)

SubmergenceSubmergence – the impact of a RISE in – the impact of a RISE in relative sea level relative sea level (Marine Transgression)(Marine Transgression)

Eustatic (global) Eustatic (global) ChangesChanges

A decrease in global temperatures leads to A decrease in global temperatures leads to more precipitation occurring in the form of more precipitation occurring in the form of snow. snow.

Eventually this snow turns to ice and so Eventually this snow turns to ice and so water is stored on land rather than being water is stored on land rather than being returned to the ocean store. returned to the ocean store.

Consequently there is a global FALL in sea Consequently there is a global FALL in sea level.level.

If global temperatures subsequently rise, If global temperatures subsequently rise, glaciers retreat and ice melts causing a glaciers retreat and ice melts causing a RISE in global sea level.RISE in global sea level.

Isostatic (local) ChangesIsostatic (local) Changes During a glacial period, the weight of ice in During a glacial period, the weight of ice in

ice sheets and glaciers adds weight to the ice sheets and glaciers adds weight to the earth’s crust.earth’s crust.

This causes the crust to sink lower into the This causes the crust to sink lower into the mantle rock beneath.mantle rock beneath.

This results in an apparent rise in the level This results in an apparent rise in the level of the sea.of the sea.

At the end of the glacial period the ice At the end of the glacial period the ice melts and weight is lost from the crust melts and weight is lost from the crust causing it to slowly rise. The sea level will causing it to slowly rise. The sea level will then appear to fall.then appear to fall.

Some places on the east coast of Scotland Some places on the east coast of Scotland are rising at a rate of 7mm a year.are rising at a rate of 7mm a year.

Landforms of Landforms of SubmergenceSubmergence

RiasRias FjordsFjords Fjards – submerged glacial lowlandsFjards – submerged glacial lowlands Dalmatian Coasts – submerged Dalmatian Coasts – submerged

valleys running parallel to the coastvalleys running parallel to the coast

RiasRias

Rias are submerged river valleys. The lowest part of Rias are submerged river valleys. The lowest part of the river’s course and the floodplains alongside the the river’s course and the floodplains alongside the river may be completely drowned, but the higher river may be completely drowned, but the higher land remains exposed, e.g. Kingsbridge Estuary, land remains exposed, e.g. Kingsbridge Estuary, DevonDevon

In In cross sectioncross section the ria has relatively the ria has relatively shallow water becoming increasingly deep shallow water becoming increasingly deep towards the centre. The exposed valley towards the centre. The exposed valley sides are quite gently sloping.sides are quite gently sloping.

In In long sectionlong section rias are quite even with a rias are quite even with a smooth profile and water of uniform depth.smooth profile and water of uniform depth.

In In plan viewplan view they tend to be winding, they tend to be winding, reflecting the original route of the river reflecting the original route of the river and its valley.and its valley.

FjordsFjords

Fjords are submerged glacial valleys. They have Fjords are submerged glacial valleys. They have steep, cliff-like valley sides and the water is uniformly steep, cliff-like valley sides and the water is uniformly deep (often 1000m in depth). These were formed deep (often 1000m in depth). These were formed when glaciers eroded below sea-level. When the ice when glaciers eroded below sea-level. When the ice melted the valleys were flooded, e.g. Milford Sound melted the valleys were flooded, e.g. Milford Sound fjord, New Zealandfjord, New Zealand

The u-shaped cross-section reflects the The u-shaped cross-section reflects the original shape of the glacial valley.original shape of the glacial valley.

Unlike rias, fjords are not deepest at their Unlike rias, fjords are not deepest at their mouths, but have a shallow section at the mouths, but have a shallow section at the seaward end known as the threshold.seaward end known as the threshold.

Fjords have much straighter routes, due to Fjords have much straighter routes, due to the erosive power of the glacier.the erosive power of the glacier.

Landforms of EmergenceLandforms of Emergence

Raised BeachesRaised Beaches Abandoned CoastlinesAbandoned Coastlines

Raised BeachesRaised Beaches

Raised beaches, e.g. Little Gruinard, Ullapool are Raised beaches, e.g. Little Gruinard, Ullapool are areas of former wave-cut platforms and their areas of former wave-cut platforms and their beaches which are left at a higher level than the beaches which are left at a higher level than the present coastline. Abandoned cliffs, caves and stacks present coastline. Abandoned cliffs, caves and stacks can also be found.can also be found.

DalmatianCoast

AbandonedCliff

Fjard

Ria

2 3

5

7 8 9

1

64