In June 2022, the record for the shortest day of the last half-century was broken. But despite this, the steady acceleration since 2020 has curiously been replaced by a slowdown.
For millions of years, the Earth’s rotation has slowed due to tidal effects. This process increases the length of a day by about 2.3 milliseconds per century. A few billion years ago, an Earth day lasted only about 19 hours. During the last 20,000 years, another process was at work that accelerated the Earth’s rotation. As the last ice age ended, the melting of the polar ice sheets reduced surface pressure, and the Earth’s mantle began to constantly move towards the poles. This shortens the day by about 0.6 milliseconds per century.
Since the 1960s, scientists have begun to get very accurate estimates of the Earth’s rotation rate. Comparison of these forecasts with the indicators of atomic clocks showed that the length of the day is constantly decreasing. But if you remove the fluctuations in rotational speed due to tides and seasonal effects, it turns out that since 2020 the trend has changed from a short day to a longer day. This change is unprecedented in the last 50 years. The reasons for this are unclear.
Source: Ferra
