3D Earth Structure Impacts Antarctic Ice Loss and Sea Levels

Overview

This study examines how the complex

affects

Antarctica's contribution

The amount that the Antarctic ice sheet adds to the rise in global sea levels, which is an important factor in understanding and predicting future changes in sea levels around the world.

 

to future

global sea level rise

The increase in the average height of the world's oceans, which can be caused by factors like melting glaciers and ice sheets, as well as the expansion of ocean water due to warming temperatures.

 

. By using advanced computer models that combine the dynamics of the

Antarctic ice sheet

The large, permanent mass of ice covering the continent of Antarctica, which can influence global sea levels as it gains or loses ice over time.

 

with the deformation of the Earth's surface, the researchers were able to get a more accurate picture of how melting ice in Antarctica will impact sea levels around the world.

The key finding is that including the 3D structure of the Earth's mantle in the models, rather than using a simpler

, can significantly change the projected amount of

sea level rise

The increase in the average height of the world's oceans, which can be caused by factors like melting glaciers and ice sheets, as well as the expansion of ocean water due to warming temperatures.

 

from the melting of the Antarctic ice sheet. This is because the 3D mantle structure affects how quickly the land in Antarctica rises up as the heavy ice melts, which in turn impacts how much water is released into the oceans.

Key Findings

The researchers found that including the 3D viscous (or fluid-like) properties of the Earth's mantle in their models led to some important effects:

1. Rapid uplift in the

   marine sectors
   The areas of the Antarctic ice sheet that are located in or near the ocean, which can be more vulnerable to changes in sea levels and ocean temperatures.

    
   of the Antarctic Ice Sheet: As the heavy ice melts, the land underneath rapidly rises up, reducing the projected ice loss in low-emission climate scenarios. This can lower Antarctica's contribution to global sea level rise by up to 40% in the coming centuries.

2. Amplified sea level rise in

   high-emission scenarios
   Scenarios that assume high levels of greenhouse gas emissions in the future, leading to significant global warming and climate change.

    
   : However, in high-emission scenarios where
   ice retreat
   The process where glaciers and ice sheets shrink in size and move back, often due to warming temperatures and changes in the climate.

    
   is rapid, the uplift of the land cannot keep up. This causes water to be expelled from the exposed Antarctic seafloor as it rebounds, amplifying the overall sea level rise.

These findings highlight the critical importance of accurately representing the 3D structure and

of the Earth when assessing how the melting of the Antarctic ice sheet will impact future global sea levels. Simplistic 1D models of the Earth's structure are not enough to capture these complex interactions.

Modeling Framework

The researchers used a comprehensive modeling approach that combined three key components:

1. A

   dynamic ice sheet model
   A computer model that simulates the complex movement and changes of large ice sheets, such as those found in Antarctica, over time.

    
   that simulates the continental-wide and detailed regional ice dynamics of the Antarctic Ice Sheet under different climate change scenarios.

2. A 3D global

   glacial isostatic adjustment (GIA)
   The gradual rise or sinking of land masses in response to the addition or removal of large ice sheets, which can affect sea levels and the movement of ice sheets.

    
   model that calculates how the Earth's surface deforms in response to changes in the ice sheet.

3. A detailed 3D representation of the Earth's viscoelastic (elastic and viscous) structure, including

   lateral variations in mantle viscosity
   Differences in the thickness and flow properties of the Earth's mantle layer in different geographic regions, which can affect how the land and sea levels change in those areas.

    
   based on
   seismic data
   Information about the Earth's interior structure and properties that is gathered by measuring the movement of seismic waves, which can help scientists understand processes like glacial isostatic adjustment.

    
   , particularly focused on the complex features in the
   Antarctic region
   The area around the South Pole, including the continent of Antarctica and the surrounding ocean. This region is of interest because changes in the ice and land there can affect global sea levels.

    
   .

By coupling this ice sheet model with the 3D GIA model, the researchers were able to assess how the interactions between the ice sheet and the deforming Earth impact future sea level changes.

Coupling Procedure

The modeling process involved an iterative coupling between the ice sheet model and the 3D GIA model:

1. The ice sheet model calculates changes in
   ice thickness
   The depth or height of the ice covering the land and ocean in the Antarctic region. The thickness of the ice is an important factor in understanding how the ice sheet may change over time.

    
   over time.
2. These ice thickness changes are used as input to the 3D GIA model, which then computes the resulting global changes in sea level and land elevation.
3. The GIA results are then fed back into the ice sheet model to update the
   bedrock elevation
   The height or depth of the solid ground underneath the ice in the Antarctic region. Changes in the elevation of the bedrock can affect how the ice sheet moves and interacts with the land.

    
   .
4. This coupling process is repeated several times to allow the models to converge on a consistent set of ice volume and sea level projections.

This iterative approach ensures that the dynamic feedbacks between the ice sheet and the deforming Earth are properly accounted for in the final sea level rise projections.

ΔGMSL Calculations

The researchers used a specialized method to calculate the contribution of the Antarctic Ice Sheet to

. This method includes an important "

water expulsion

The process where changes in the height of the land or bedrock in the Antarctic region can cause water to be pushed out of or pulled into the surrounding oceans, affecting global sea levels.

 

" effect, where changes in the elevation of the Antarctic seafloor can displace water into or out of the world's oceans.

Additionally, the researchers applied a small "

" to account for the difference in density between fresh meltwater from the ice sheet and the existing ocean water. This correction is relatively minor, amounting to around 5% or less of the total ΔGMSL.

Implications

The key implication of this study is that accurately representing the 3D structure and viscous properties of the Earth's mantle is critical for reducing uncertainty in projections of future sea level rise from the melting of the Antarctic ice sheet.

Simplistic 1D models of the Earth's structure fail to capture important regional features and dynamics that can significantly alter the projected ice loss and sea level changes. Accounting for lateral variations in Earth structure, particularly in regions like the

of

West Antarctica

The part of the Antarctic continent that is located on the western side of the continent, which includes the Amundsen Sea Embayment and is an area of particular interest for understanding changes in the Antarctic ice sheet.

 

where observations are sparse, is essential for improving the reliability of ice sheet and sea level rise projections.

Overall, this study highlights the importance of using comprehensive, coupled modeling frameworks that integrate the latest understanding of ice sheet dynamics and Earth system processes to better anticipate the future impacts of climate change on global sea levels.