Glaciated Landscapes: Glaciers and Climate Change

Glacier

A glacier is a moving body of ice.

Glacial System

A glacier is an open system with inputs, outputs and interactions with other systems.

Zone of Accumulation

The area towards the 'head' of the glacier where inputs are concentrated.

Zone of Ablation

The area towards the 'snout' or 'toe' of the glacier where outputs are concentrated.

Inputs to the Glacier

Accumulation, precipitation (snow, sleet, hail), wind-blown snow, avalanche debris (snow, ice, rock), sublimation (evaporation from ice), and de-sublimation (condensation into ice).

Outputs to the Glacier

Ablation, meltwater, rock debris, calving (break-away of ice blocks), and solar energy.

Glacial Budget

The balance between inputs and outputs in a glacier.

Mass Balance

The difference between accumulation and ablation over time.

Equilibrium

A state where inputs and outputs in the glacier system are balanced.

Little Ice Age

A historical period characterized by cooler temperatures and changes in glacier budgets.

Firn

Snow that has become compacted and experienced one winter's freezing and a summer's melting.

Glacial Movement

The speed at which glaciers move, caused by gravitational forces.

Climate Change

Long-term changes in temperature and weather patterns affecting glacier dynamics.

Types of Ice Mass

Includes cirque glaciers, valley glaciers, highland ice fields, piedmont glaciers, ice sheets, and sea ice.

Quaternary Ice Age

A geological period that includes glacials, interglacials, and stadial periods.

Avalanche Debris

Material (snow, ice, rock) that is displaced during an avalanche.

Calving

The process of ice blocks breaking away from a glacier.

Solar Energy

Energy from the sun that contributes to melting and ablation in glaciers.

Compaction of Snow

The process where falling snowflakes compress under additional snow, increasing density.

Density of Snow

The measure of mass per unit volume of snowflakes, which is low when they first fall.

Air Passages in Snow

Spaces between ice crystals in firn that allow air to be trapped.

Mass Accumulation Equation

The formula used to calculate the rate at which glacier ice forms from snow.

Mass Balance

The difference between inputs (accumulation) and outputs (ablation).

Positive Balance

Occurs when inputs > outputs, causing a glacier to grow (advances).

Negative Balance

Occurs when outputs > inputs, causing a glacier to shrink (retreats).

Zone of Accumulation

Colder higher altitude areas where inputs > outputs.

Zone of Ablation

Warmer lower altitude areas where outputs > inputs.

Zone of Equilibrium

The area where inputs = outputs, also known as the line of equilibrium.

Line of Equilibrium

Also known as the snow or firn line, where the mass balance is equal.

Excess Mass Transfer

The process where excess mass from the zone of accumulation is transferred to the zone of ablation due to gravity.

Cumulative Net Balance (CNB)

The total balance of a glacier over multiple years.

Annual Mass Balance

The yearly difference between accumulation and ablation for a glacier.

Glacier Deformation

The process by which a glacier flows due to gravity.

Short-term Changes in Mass Balance

Fluctuations in mass balance that can occur over the course of a year.

Glacier Flow

The movement of glacier ice as it deforms under its own weight.

Negative Mass Balance

A state where the majority of the world's glaciers are currently shrinking.

Positive Mass Balance

A state where a glacier is gaining mass through accumulation.

Glacier Area Loss Calculation

Estimating the km² of lost glacier area by counting grid squares and multiplying by 1.5.

Impact of Climate Change

The effect of global warming on glacier mass balance and its potential consequences for other systems.

Zone of Accumulation Variability

The area where inputs and outputs vary seasonally, typically increasing in winter.

Zone of Ablation Variability

The area where inputs and outputs vary seasonally, typically increasing in summer.

Glacier Retreat

The process of a glacier shrinking due to negative mass balance.

Glacier Advance

The process of a glacier growing due to positive mass balance.

Glacier mass balance

The difference between the accumulation and ablation of a glacier over time.

Long-term changes in mass balance

Changes in glacier mass balance viewed over hundreds to thousands of years.

Cold glacial periods

Periods when glaciers have a positive mass balance leading to long-term growth.

Warm interglacial periods

Periods when glaciers have a negative mass balance leading to decay and retreat.

Ice sheets

Dome shape glaciers greater than 50,000 km².

Devensian

The last glacial period during which a large body of ice covered much of northwest Europe.

Quaternary

A geological period representing the last 2.6 million years of Earth's history.

Insolation

Incoming solar radiation received at the Earth's surface.

Milankovitch Cycles

Long-term climate change caused by variations in Earth's orbit leading to changes in insolation.

Eccentricity

The stretch of Earth's orbit affecting the distance from the Sun.

Obliquity

The tilt of Earth's axis, currently at 23.5 degrees.

Precession

The wobble of Earth's axis affecting the position of the seasons.

Current orbit duration

The Earth's current orbit of the Sun takes 365 ¼ days.

Seasonal variation

Changes in climate due to the tilt of Earth's axis towards the Sun.

Ipswichian

An interglacial period from 11,500 years before present to present.

Hoxnian

An interglacial period from 140,000 ybp to 100,000 ybp.

Variation in insolation

Caused mostly by Milankovitch Cycles affecting climate over long time frames.

Wobble cycle duration

The time it takes for one wobble cycle to complete.

Tilt variation timeframe

The timeframe over which the tilt of Earth's axis changes.

Insolation variation percentage

Milankovitch cycles cause variations of up to a certain percent in incoming insolation.

Glacial and interglacial periods

Long-term cyclical changes mainly due to Earth's orbital variations.

Milankovitch Cycles

Variations in Earth's orbit that affect insolation received.

Orbital Cycle

Change in the shape of the orbit from circular to elliptical, and back again every 100,000 years.

Insolation

The amount of solar energy received at Earth's surface.

Tilt of the Axis

Changes from 22.1 to 24.5 degrees with respect to Earth's orbital plane over approximately 41,000 years.

Extreme Seasons

Seasons that become more pronounced with greater axial tilt.

Axis Wobble

Periodic change in the position of the seasons on the orbit.

Glacial Periods

Cold periods characterized by extensive ice cover, such as the Devensian from 80,000 to 11,500 years before present (ybp).

Interglacial Periods

Warmer periods between glacial periods, such as the Holocene, the last 11,500 years.

Positive Feedback

Processes that amplify changes in the glacial mass balance system.

Cooling Leads to Further Cooling

Increased snow and ice cover raises surface albedo, leading to more solar energy being reflected and further cooling.

Warming Leads to Further Warming

Increased temperatures can disrupt thermohaline ocean circulation, leading to warmer conditions.

Thermohaline Ocean Circulation

Current that brings warm salty water to northwest Europe, affecting winter temperatures.

Younger Dryas

A rapid period of cooling at the end of the last glacial period caused by disruption to ocean currents.

Solar Forcing

Energy released by the sun, linked to sunspot activity.

Sunspots

Areas of high solar output that fluctuate on an approximate 11-year cycle.

Average Winter Temperature in England

5°C.

Average Winter Temperature in Russia

-8°C.

Cooling of Climate

The process initiated by Milankovitch Cycles that leads to glacial periods.

Negative Feedback

Processes that reduce or diminish changes in a glacial budget.

Disruption to Thermohaline Circulation

Can lead to cooling, as seen during the Younger Dryas.

Ice Accumulation Changes

Variations in the amount of ice accumulating during different climate periods.

Solar Output Fluctuations

Historically extended periods of low and high solar output linked to sunspot activity.

Maunder Minimum

A period between 1645 and 1715 characterized by low levels of solar output.

Frost Fair

An event that occurred on the River Thames during the Little Ice Age when the river froze over.

Baltic Sea

A sea that froze over during the Little Ice Age, impacting shipping and navigation.

Cairngorm Mountains

A mountain range in Scotland that experienced permanent snow cover at an altitude of about 1200 metres during the Little Ice Age.

Rhone Glacier

A glacier in the French Alps that advanced during the Little Ice Age, threatening nearby towns.

Volcanic Eruptions

Explosive eruptions that can influence cool conditions by propelling sulphur dioxide and ash into the stratosphere.

Tambora

A volcanic eruption on Sumbawa Island in 1815 that reduced global temperatures by up to 0.7°C for 2-3 years.

Anthropogenic Factors

Human activities that increase the concentration of greenhouse gases, resulting in an increase of global average temperatures by over 1.2°C since 1880.

Ice Cover

Currently, glaciers cover more than 10% of the Earth's land surface and store 75% of the world's fresh water.

Devensian Glaciation

A period approximately 18,000 years ago when ice cover was at its maximum.

Glacier Distribution

Glaciers today tend to be found in high altitude and/or high latitude regions of the world.

Mass Balance

The cumulative balance of ice accumulation and ablation over time.

Firn / neve snow

Granular snow that has been compacted and is in the process of turning into glacial ice.

Positive Mass Balance

When the accumulation of ice exceeds the ablation, leading to growth of glaciers.