Three Perspectives by Simon Knighton
Premiered as part of Changing Music in a Changing Climate
15 October 2020
This piece presents three perspectives of sea ice; microscopic, human and satellite. This provides an artistic way to illustrate and communicate the changes underway in the global cryosphere as a result of climate change. Sea ice coverage at both poles has reduced in response to a warming ocean and atmosphere, with changes in the Arctic particularly stark. The piece was inspired by the techniques and methods behind Freya’s research, which uses diatoms (a form of microscopic algae preserved in ocean sediment) to reconstruct past changes in polar sea ice. This inspired the idea of looking at sea ice from different perspectives, using technology and artistic representations. Parts one and four use footage of Antarctica from a human perspective filmed during a scientific cruise, whilst part three uses NASA satellite footage of the Arctic to see how these changes have occurred over the last 30 years or so. Part two shows extreme close ups of ice melting. An additional element of climate science is presented in the music in the form of Milankovitch cycles. Sometimes known as the ‘heartbeat’ of the global climate, these cycles, which affect the amount of solar radiation that reaches earth, have paced climate and sea ice oscillations on a geologic timescale. However, anthropogenic climate change is currently disrupting this heartbeat. The piece therefore plays with the idea of paced and disrupted natural climatic cycles, exemplified by sea ice oscillations.
Milankovitch Cycles and the Global Ice Cover
Milankovitch cycles, first described by Serbian geophysicist Milutin Milankovitch ~100 years ago, are sometimes known as the ‘heartbeat’ of the climate system. The cycles are driven by very small changes in the amount of solar radiation that reaches earth due to changes in Earth’s orbit, including orbital eccentricity, axial tilt and rotation. These small changes are then amplified by internal climate feedbacks. For example, ice is highly reflective; reduced ice coverage ice therefore increases the amount of solar radiation absorbed by the earth, which in turn amplifies warming. This is known as a positive feedback.
Key Milankovitch cycles:
- The departure of Earth’s elliptical orbit from circularity- eccentricity (100,000 year cycle)
- The angle of Earth’s axial tilt – obliquity (41,000 year cycle)
- The trend in direction of Earth’s axis of rotation – precession (23,000 years)
Figure 1: Milankovitch cycles; Obliquity, Eccentricity and Precession
Throughout the Cenozoic Era (the last 66 million years), Earth’s climate has been paced by different Milankovitch cycles at different times. Over the last 800,000 years (800 kyr), the climate has been paced by 100 kyr eccentricity cycles, with glaciations (‘ice ages’) occurring approximately every 100 kyr (Figure 2). However, during the warm Pliocene (~3 million years ago), Earth’s climate was paced instead by obliquity (41 kyr cycles). Scientists often don’t fully understand why climate pacing switches between the cycles, but it is likely related to changes in internal feedbacks, including sea ice coverage.
Figure 2 a) Oscillations of CO2 ppm, methane and global temperature over the last 800 kyr, showing 100 kyr cyclicity b) Atmospheric CO2 and methane over the last 2 kyr, showing a clear increase since c. 1900 (data from Antarctic ice cores; Brook, 2008)
Today, anthropogenic climate change has disrupted the preceding 100 kyr cyclicity (Figure 2). Whilst, in theory, Earth should be headed towards another ice age, instead global temperatures are increasing and global ice cover is declining as a result of increasing carbon emissions. Reduced polar sea ice coverage acts as a positive feedback, increasing the absorption of solar radiation and accelerating climate warming. This drives ‘polar amplification’, whereby Earth’s polar regions warm at a faster rate than the rest of the planet, further increasing ice loss.
The Music
Instruments, synthesisers and field recordings blend to create a symbiosis of the sounds of nature and music (many of the percussive sounds in the piece are sampled and chopped up field recordings, for example). The music is structured in cycles relating to the ratios of Milankovitch cycles. Throughout the piece, the ratio of 10:4:2 is used to layer different parts and musical parameters against each other creating cyclical movements which approximate the primary Milankovitch cycles. For instance, the speed at which the percussion parts swing across the stereo spectrum (one part moves across every 2 bars, another part every 4 bars, and another part every 10 bars) relate to these ratios. Likewise, the melodic synthesised parts and percussion parts (which appear in part two) are three instances of the same melody (in different octaves) which has been rhythmically augmented to overlap each other in cycles. In this way, the music acts as an analogy to the natural occurrence of Milankovitch cycles on which man-made climate change occurs.
Click below to listen to an introduction to the piece by the composer, followed by the performance.
Credits
Music composition/production: Simon Knighton
Video editing and microscopic filming: Fiona Brehony
Science advisor: Freya Mitchison
The film uses footage and images owned and produced by NASA in line with their media usage guidelines.
Additional footage of Antarctica filmed by Elaine Mawbey.
Microscopic ice images filmed by Fiona Brehony.
Additional editing by Simon Knighton.
