330
19 Correlation of Significant Voyaging Activity with Rare Extreme Climate Events
be augmented or reduced by local weather anomalies. Even with this limitation,
the Nile records offer a remarkable means of calculating strong El Niño events (to
within a one- or two-year period). For our purposes – to establish a chronology for
long-distance oceanic migration during the first millennium AD and in the Medieval
Climatic Optimum – they provide a remarkable resource, especially given the difficulties of precisely defining for a specific area or even hemisphere the boundaries
between warm and cold climate periods.
Ross Couper-Johnston [8] describes the way in which the Nile flood was
measured:
Each year, careful measurement were taken on the Nilometer, an elaborate, Escher-like
four-sided stone well with steps down the sides spiralling around a calibrated column in
the centre. Underground conduits allowed the water to enter from the Nile. If the level
approached the height considered optimum for the prosperity of the people, the guardian
of the Nilometer would swim to the column and anoint it with a concoction of saffron and
musk. The next day, wafa was declared to the public through singers positioned around the
Nilometer, and the guardian dressed in a robe of gold thread would lead a great procession
through the crowded streets. A signal was given and the feeder canals would be opened to
inundate the fields.
Even Shakespeare, Couper-Johnston shows us (p. 76), was aware of the ancient
measuring of the Nile flood:
. . .they take the flow o’ th’ Nile
By certain scales, i’ the pyramid; they know
By th’ height, the lowness, or the mean, if dearth
Or foison follow. The higher Nilus swells,
The more it promises. As it ebbs, the seedsman
Upon the slime and ooze scatters his grain
And shortly comes to harvest. (Anthony and Cleopatra)
Low Nile floods, Couper-Johnston tells us, represent a failure of the monsoon
rains over the Ethiopian highlands which “feed the headwaters of the Blue Nile
and Atbara River each summer, supplying 95 per cent of the flood’s volume”
(pp. 77–78). The lower the Nile flood the stronger the El Niño event that caused
the deficit. Significantly the 900-year period for which we have ancient Nile flood
records covers a major period of exploration and colonization in the Pacific.
19.3 Sketching a Chronology for Long-Distance Voyaging
Our interest in El Niño events in this chapter is specific. Our primary concern is
in using the El Niño proxy data of low Nile floods as a chronological marker with
annual resolution. From the pattern of deficient Nile floods, we can determine the
pattern of El Niño events and so, given our proposal of a relationship between
El Niño events and enhanced maritime possibilities, seek to determine the pulses of
long-distance migration and of significant voyaging activity in the Pacific in the two
global warm periods covered by the Nile flood proxy data. Because El Niños caused
long-lasting reversals of the trade winds and currents, they provided insurance for
19 Correlation of Significant Voyaging Activity with Rare Extreme Climate Events
be augmented or reduced by local weather anomalies. Even with this limitation,
the Nile records offer a remarkable means of calculating strong El Niño events (to
within a one- or two-year period). For our purposes – to establish a chronology for
long-distance oceanic migration during the first millennium AD and in the Medieval
Climatic Optimum – they provide a remarkable resource, especially given the difficulties of precisely defining for a specific area or even hemisphere the boundaries
between warm and cold climate periods.
Ross Couper-Johnston [8] describes the way in which the Nile flood was
measured:
Each year, careful measurement were taken on the Nilometer, an elaborate, Escher-like
four-sided stone well with steps down the sides spiralling around a calibrated column in
the centre. Underground conduits allowed the water to enter from the Nile. If the level
approached the height considered optimum for the prosperity of the people, the guardian
of the Nilometer would swim to the column and anoint it with a concoction of saffron and
musk. The next day, wafa was declared to the public through singers positioned around the
Nilometer, and the guardian dressed in a robe of gold thread would lead a great procession
through the crowded streets. A signal was given and the feeder canals would be opened to
inundate the fields.
Even Shakespeare, Couper-Johnston shows us (p. 76), was aware of the ancient
measuring of the Nile flood:
. . .they take the flow o’ th’ Nile
By certain scales, i’ the pyramid; they know
By th’ height, the lowness, or the mean, if dearth
Or foison follow. The higher Nilus swells,
The more it promises. As it ebbs, the seedsman
Upon the slime and ooze scatters his grain
And shortly comes to harvest. (Anthony and Cleopatra)
Low Nile floods, Couper-Johnston tells us, represent a failure of the monsoon
rains over the Ethiopian highlands which “feed the headwaters of the Blue Nile
and Atbara River each summer, supplying 95 per cent of the flood’s volume”
(pp. 77–78). The lower the Nile flood the stronger the El Niño event that caused
the deficit. Significantly the 900-year period for which we have ancient Nile flood
records covers a major period of exploration and colonization in the Pacific.
19.3 Sketching a Chronology for Long-Distance Voyaging
Our interest in El Niño events in this chapter is specific. Our primary concern is
in using the El Niño proxy data of low Nile floods as a chronological marker with
annual resolution. From the pattern of deficient Nile floods, we can determine the
pattern of El Niño events and so, given our proposal of a relationship between
El Niño events and enhanced maritime possibilities, seek to determine the pulses of
long-distance migration and of significant voyaging activity in the Pacific in the two
global warm periods covered by the Nile flood proxy data. Because El Niños caused
long-lasting reversals of the trade winds and currents, they provided insurance for