2A.1 The causes of longer and shorter climate change, which have led
to icehouse greenhouse changes.
➤ A chronology of multiple glacial and interglacial periods caused by Pleistocene
climate change
Pleistocene:
The first epoch of the quaternary period,between the Pilocene Epoch and the Holocene
epoch.
Known as the ice age due to its numerous glacial-interglacial cycles.
The last period of glacial advance is known as the Loch Lomond Stadial. This occurred
between 12,000 and 18,000 years ago, marking the end of the pleistocene epoch.
We are now in an interglacial period , known as the holocene which began about 11,700
years ago.
In the last 1 million years there have been as many as 10 glacial periods, interrupted by
interglacials. During these glacial periods, in the northern hemisphere, huge ice masses
spread over most of Europe, Asia and north america.
Quaternary- 2.58 million years ago - present
Pleistocene- 2.58 million years ago-11,700 years ago
Holocene- 11,700 years ago - present
Anthropocene- current
➤ The long-term factors leading to climate change: Milankovitch cycles as the
primary driver and the shorter-term role of variations in solar output (1), and
volcanic eruptions
Milankovitch cycles:
-Stretch/eccentricity- the earth's orbit changes from circular to eclipse every 96,000 years,
which changes the distance between the earth and the sun thus, affecting the climate.
-Tilt/ obliquity- the earth's tilt changes from 21.8 and 24.4 degrees every 41,000 years
-Wobble/ axial precession- overtime, the earth's axis tilt changes. In 22,000 , the axial tilt
spins one whole time around, this affects where solar radiation is distributed.
,Shorter term causes of glacial periods:
-Variations in solar output: Sunspots occur by magnetic storms which increase solar output.
-Volcanic eruptions: Mount Tambora erupted in 1815,lowering global temperatures by 0.5
degrees. Eruptions eject large volumes of sulphur dioxide,water vapour, dust and ash into
the atmosphere, this reflects some of the insolation causing cooling.
⟶The characteristics and causes of shorter-term climate events: Loch
Lomond Stadial (Pleistocene) and the Little Ice Age (holocene)
The term stadial refers to a brief cold period during an interglacial warm period.
Loch lomond Stadial: As ice sheets were melting, towards the end of the pleistocene
epochs last glacial period, a short but severe glaciation returned to the north atlantic region.
This caused glaciers to grow in the Scottish highlands.
Temperatures across the British isles ranged from -20 in winter to 10 in the summer.
These conditions lasted for approx 1300 years.
One possible cause for this stadial was the sudden influx of cold, fresh water into the north
atlantic, from the melting polar ice sheets which would have disrupted the salt content,
driving thermohaline circulation.
Little Ice Age: Between 1645 and 1715 there was virtually no sunspot activity recorded and
known as the Maunder Minimum.
The little ice age lasted from 1450-1850.
Average temperatures were 0.5-1 degrees lower than they are now, which caused rivers
and lakes to freeze regularly and Arctic sea ice was more extensive.
2A.2 Present and past pleistocene distribution of ice cover
➤The definition and importance of the cryosphere and its role in global systems
and classification of ice masses by scale and location (ice sheets, ice caps,
cirque and valley glaciers, and ice fields) and polar and temperate environments.
The cryosphere: All the frozen regions on earth, covers 13% of the planet's surface.
Features of the cryosphere include:
-Snow
-Ice
-Permafrost and frozen ground
-Glaciers
-Ice caps, Sheets and shelves
-Icebergs
-Sea , river and lake ice
, The cryosphere is important because:
Permafrost areas are significant carbon stores and help regulate levels of carbon in the
atmosphere
The cryosphere helps regulate earth's climate through its high surface albedo effect.
As the climate warms,the cryosphere also changes through feedback mechanisms,which further
influences the climate:
-increases snow and ice melt, exposes more dark surfaces to insolation.
-this increases surface absorption of solar radiation, causing further melting and release of
stored carbon and methane into the atmosphere, which leads to further atmospheric warming
-this is a positive feedback loop, which exacerbates the impacts of climate change.
↪Classification of ice masses
Unconstrained:
● ice sheets: continuous masses of ice that cover areas greater than 50,000 km2, can
cover whole valleys,plains and mountain ranges.
● Ice caps: cover areas less than 50,000km2, usually centred on a mountain high point
(massif), then ice flows in multiple directions to form a cap.
● Ice Shelves: Thick floating slabs of ice, permanently attached to landmass, found where
ice flows down to the coast and out onto the ocean's surface. Only found in Greenland,
Northern Canada, Russian Arctic and antarctic.
Constrained:
● Ice Fields: ice that covers a mountain plateau, but does not extend the high altitude
area, Not thick enough to bury the topography. Example; Himalayas, Andes.
● Piedmont Glaciers: Found at the foot of mountains, where a mass of ice has flowed
downslope and fans out, forming lobes of continuous ice.
● Valley Glacier: Ice is surrounded by high mountains and fills the valley. Usually ribbon
shaped and vary in length from a few km to over 100km.Most begin as mountain
glaciers and spread/flow to gorges, basins and across the valley floor.
● Cirque glaciers:most common glacier and found in nearly all areas where snow and ice
accumulates eg alpine regions. Confined to either the upper parts of a glacial trough or
within the hollowed cirque basin itself. Niche glaciers are smaller versions of cirque
glaciers.
↪Thermal Regime of Ice Masses
● Pressure melting point: the temperature at which ice melts at a given pressure. The
melting point of ice depends on air pressure above the ice, as air pressure increases, the
temperature at which ice melts lowers.
● Warm Based Glaciers: Occur at temperate regions such as southern iceland and
western norway. Meltwater lubricates the base and sides of the glacier which assists
basal sliding movement and increases rate of erosion, transportation and deposition.
to icehouse greenhouse changes.
➤ A chronology of multiple glacial and interglacial periods caused by Pleistocene
climate change
Pleistocene:
The first epoch of the quaternary period,between the Pilocene Epoch and the Holocene
epoch.
Known as the ice age due to its numerous glacial-interglacial cycles.
The last period of glacial advance is known as the Loch Lomond Stadial. This occurred
between 12,000 and 18,000 years ago, marking the end of the pleistocene epoch.
We are now in an interglacial period , known as the holocene which began about 11,700
years ago.
In the last 1 million years there have been as many as 10 glacial periods, interrupted by
interglacials. During these glacial periods, in the northern hemisphere, huge ice masses
spread over most of Europe, Asia and north america.
Quaternary- 2.58 million years ago - present
Pleistocene- 2.58 million years ago-11,700 years ago
Holocene- 11,700 years ago - present
Anthropocene- current
➤ The long-term factors leading to climate change: Milankovitch cycles as the
primary driver and the shorter-term role of variations in solar output (1), and
volcanic eruptions
Milankovitch cycles:
-Stretch/eccentricity- the earth's orbit changes from circular to eclipse every 96,000 years,
which changes the distance between the earth and the sun thus, affecting the climate.
-Tilt/ obliquity- the earth's tilt changes from 21.8 and 24.4 degrees every 41,000 years
-Wobble/ axial precession- overtime, the earth's axis tilt changes. In 22,000 , the axial tilt
spins one whole time around, this affects where solar radiation is distributed.
,Shorter term causes of glacial periods:
-Variations in solar output: Sunspots occur by magnetic storms which increase solar output.
-Volcanic eruptions: Mount Tambora erupted in 1815,lowering global temperatures by 0.5
degrees. Eruptions eject large volumes of sulphur dioxide,water vapour, dust and ash into
the atmosphere, this reflects some of the insolation causing cooling.
⟶The characteristics and causes of shorter-term climate events: Loch
Lomond Stadial (Pleistocene) and the Little Ice Age (holocene)
The term stadial refers to a brief cold period during an interglacial warm period.
Loch lomond Stadial: As ice sheets were melting, towards the end of the pleistocene
epochs last glacial period, a short but severe glaciation returned to the north atlantic region.
This caused glaciers to grow in the Scottish highlands.
Temperatures across the British isles ranged from -20 in winter to 10 in the summer.
These conditions lasted for approx 1300 years.
One possible cause for this stadial was the sudden influx of cold, fresh water into the north
atlantic, from the melting polar ice sheets which would have disrupted the salt content,
driving thermohaline circulation.
Little Ice Age: Between 1645 and 1715 there was virtually no sunspot activity recorded and
known as the Maunder Minimum.
The little ice age lasted from 1450-1850.
Average temperatures were 0.5-1 degrees lower than they are now, which caused rivers
and lakes to freeze regularly and Arctic sea ice was more extensive.
2A.2 Present and past pleistocene distribution of ice cover
➤The definition and importance of the cryosphere and its role in global systems
and classification of ice masses by scale and location (ice sheets, ice caps,
cirque and valley glaciers, and ice fields) and polar and temperate environments.
The cryosphere: All the frozen regions on earth, covers 13% of the planet's surface.
Features of the cryosphere include:
-Snow
-Ice
-Permafrost and frozen ground
-Glaciers
-Ice caps, Sheets and shelves
-Icebergs
-Sea , river and lake ice
, The cryosphere is important because:
Permafrost areas are significant carbon stores and help regulate levels of carbon in the
atmosphere
The cryosphere helps regulate earth's climate through its high surface albedo effect.
As the climate warms,the cryosphere also changes through feedback mechanisms,which further
influences the climate:
-increases snow and ice melt, exposes more dark surfaces to insolation.
-this increases surface absorption of solar radiation, causing further melting and release of
stored carbon and methane into the atmosphere, which leads to further atmospheric warming
-this is a positive feedback loop, which exacerbates the impacts of climate change.
↪Classification of ice masses
Unconstrained:
● ice sheets: continuous masses of ice that cover areas greater than 50,000 km2, can
cover whole valleys,plains and mountain ranges.
● Ice caps: cover areas less than 50,000km2, usually centred on a mountain high point
(massif), then ice flows in multiple directions to form a cap.
● Ice Shelves: Thick floating slabs of ice, permanently attached to landmass, found where
ice flows down to the coast and out onto the ocean's surface. Only found in Greenland,
Northern Canada, Russian Arctic and antarctic.
Constrained:
● Ice Fields: ice that covers a mountain plateau, but does not extend the high altitude
area, Not thick enough to bury the topography. Example; Himalayas, Andes.
● Piedmont Glaciers: Found at the foot of mountains, where a mass of ice has flowed
downslope and fans out, forming lobes of continuous ice.
● Valley Glacier: Ice is surrounded by high mountains and fills the valley. Usually ribbon
shaped and vary in length from a few km to over 100km.Most begin as mountain
glaciers and spread/flow to gorges, basins and across the valley floor.
● Cirque glaciers:most common glacier and found in nearly all areas where snow and ice
accumulates eg alpine regions. Confined to either the upper parts of a glacial trough or
within the hollowed cirque basin itself. Niche glaciers are smaller versions of cirque
glaciers.
↪Thermal Regime of Ice Masses
● Pressure melting point: the temperature at which ice melts at a given pressure. The
melting point of ice depends on air pressure above the ice, as air pressure increases, the
temperature at which ice melts lowers.
● Warm Based Glaciers: Occur at temperate regions such as southern iceland and
western norway. Meltwater lubricates the base and sides of the glacier which assists
basal sliding movement and increases rate of erosion, transportation and deposition.
