A document titled „Climate‐Induced Polar Motion: 1900–2100„ by Mostafa Kiani Shahvandi and Benedikt Soju examines the impact of climate change, specifically barystatic processes, on the movement of the Earth's rotational axis relative to the crust, called polar motion. The authors examine this phenomenon over the period from 1900 to the end of 2100.

🎯 Research objective

The main objective of the study is to examine how barystatic processes will affect polar motion in the 21st century under different climate scenarios.. Bariostatic processes include continental and oceanic mass redistribution caused by melting polar ice sheets (Greenland and Antarctica), global glaciers, and changes in terrestrial water storage (TWS). The paper builds on previous studies that have shown the increasing influence of mass redistribution at the Earth's surface on polar motion. Previous analysis of the impact of bariostatic processes was limited to the period 1900–2018, and the future contribution was not explored.

📊 Climate scenarios used

The study analyses climate-induced polar motion under different climate scenarios, namely Representative Concentration Pathways (RCP) and Shared Socioeconomic Pathways (SSP). For overall barystatic processes, the study analyses scenarios in detail RCP2.6 (optimistic) and RCP8.5 (pessimistic), because they represent the approximate lower and upper limits of climate change in the 21st century, and thus provide a range of possible paths of the Earth's rotational axis under the influence of these processes.

⚙️ Research methodology

The study methodology uses data from two periods: 1900–2018 and 2019–2100. For the earlier period, the results of a previous study based on changes in the mass of ice sheets, glaciers and TWS are adopted, which explain most of the observed polar motion. For the later period (2019–2100), polar motion is calculated using the sea level equation on a rotating Earth and available projections for individual barystatic processes.

🧊 The projections include data for the Greenland and Antarctic ice sheets under RCP2.6 and RCP8.5, for global glaciers under multiple RCP and SSP scenarios, and for TWS under selected SSP scenarios. A multimodal ensemble approach is used for the Greenland and Antarctic ice sheets. For TWS, the average is made across the three SSP scenarios because they exhibit similar behavior and their impact is smaller than for other processes. However, it is important to note that the TWS projections may not capture all relevant components, such as quasi-decadal variability, and are less accurate than data from the period 1900–2018.

📌 Main findings

Main findings show that climate-induced polar motion is sensitive to the choice of climate scenario:

• Under optimistic scenario RCP2.6 the rotational pole could be moved by approximately 12 meters given its location in 1900.
• Under pessimistic scenario RCP8.5 could result in a displacement of more than twice that, approximately 27 meters considering the year 1900.
• In the period 2019-2100 the path of the future rotational pole shows a westward drift compared to a relatively stable, trendless trajectory during the 20th century.
• Under the RCP2.6 scenario, the direction of the western drift is more to the west (longitudes ≥45°W), while under the RCP8.5 scenario, the impact of significant melting of the Antarctic Ice Sheet shifts the pole more to the east (longitudes ≤30°W).

🧩 Contributions of individual barystatic processes

The most important contribution to this movement has melting of polar ice caps:

• Melting of the Greenland Ice Sheet is the main contributor and drives the rotational pole predominantly westward. This influence is more than twice as large under the RCP8.5 scenario as under RCP2.6. The drift caused by Greenland is nonlinear.
• Under the RCP8.5 scenario, another significant contributor is melting of the Antarctic ice sheet, which causes a shift towards the east.
• Melting global glaciers it also contributes to polar motion, although to a lesser extent.
• Changes in terrestrial water supplies (TWS) they have the smallest contribution to the overall trend, although they are a likely cause of quasi-decadal oscillations.

🛰️ Implications for technology and the Earth

The study results have significant implications:

• Reduced predictability of polar movement may affect the operational accuracy of applications such as spacecraft navigation and telescope orientation.
• Shifts in polar motion can also reduce the accuracy of determining the Earth's gravitational field from satellite gravimetry.
• Measurable global deformations of the Earth they can reach up to 2.8 cm in mid-latitudes.
• Polar tides could lead to global changes in gravity.

⚖️ Taking other factors into account

The authors also note that other factors besides climate-induced polar motion may also contribute significantly:

• Glacial Isostatic Adjustment (GIA) – although important, under RCP8.5 it may be outweighed by the impact of climate change.
• For the highest accuracy, it is also necessary to take into account core dynamics and seismic processes.

Overall, the study provides estimates of the possible evolution of polar motion under the influence of climate change and its potential consequences for positioning in space, deformation of the Earth's surface, and sea level change. Dependence on climate scenario highlights the uncertainty associated with the future evolution of polar motion, particularly due to the challenges in predicting climate trends. Spring