9:45 AM - 10:00 AM
[ACC25-04] Distributions and variations of ground ice from Earth System perspective
★Invited Papers
Keywords:Ground ice, Earth System, Climatology, Paleoclimatology
Ground ice is a general term for ice below the ground surface. It varies from needle ice in the seasonally frozen ground zone, to ice lenses, to segregated ice and intrusive ice (or pingo ice), and to ice-wedge ice in the permafrost zone. The size and volume of ground ice, its origin, causes and formation processes, duration, and spatial distribution vary widely. The important processes from an Earth System perspective include the heat and water budgets with the atmosphere, effects on groundwater hydrology and river runoff, and landscape changes. Recently, ice-rich permafrost with high soil organic carbon content (Yedoma layer) attracts social attention in relation to the possible generation and additional release of greenhouse gases caused by subsurface organic carbon decomposition, and to the potential damages to industrial and social infrastructure caused by subsidence due to melting (thermokarst).
It is difficult to directly observe the location and measure the three-dimensional structure of subsurface ice because of its sub-surface existence. At the local level, understanding of stratigraphic structure through samples obtained by core drilling is straightforward but limited in number and locations. Electrical sensing and ground-penetrating radar can estimate the spread and depth to some extent, however, extending such observations to a wide area is difficult. The estimation using remotely-sensed observations by airplanes and/or satellites has made great progress in recent years, but it does not directly identify the distribution of existence and reserves, but mainly calculates the volume of subsurface ice melting based on the depth of subsidence in the areas where the land surface was disturbed by wildfires, and indirectly estimates the overall distribution in the surrounding area in combination with topographical information.
There are only limited data available to understand the large-scale distribution and quantity of ground ice. The most widely used large-scale distribution data at present are distribution maps created at the end of the last century by combining geological and geomorphological information with outcrop and cross-sectional surveys in the field, provided at a resolution of 1 or 0.5 degrees latitude and longitude for the Northern Hemisphere. In addition, datasets that capture more detailed ground ice distribution in specific regions, such as the Canadian and Siberian regions, are being created by adding local field observations and geomorphological considerations.
Numerical model experiments and simulations have been conducted to estimate and understand the large-scale dynamics of ground ice. In particular, groundwater hydrology has begun to be implemented as a part of the subsurface hydrological conditions in parallel with the sub-surface temperature conditions, with the improvement and sophistication of global climate models in the 2000s. Since then, the carbon budget in the ecosystem (vegetation), hydrological dynamics and water balance, and the melting and decomposition of stored carbon are also attracting attention these days. The issues of these large-scale models are 1) the formation and loss of excess ice that surpasses the porosity, and its linkage with topographic changes in the vertical direction, 2) the handling of spatial heterogeneity in the horizontal direction, and 3) the identification and implementation of sub-grid side processes, which manifest the scale gap between the spatial scale of the phenomena and the model resolution.
Recently, the authors estimated the present-day distribution of ground ice and soil organic carbon at 2 km resolution by developing and employing a numerical model to estimate the respective temporal changes of ground ice and soil organic carbon in the Arctic Circle since the last interglacial. This presentation introduces ground ice distribution and variations from an Earth system perspective, including these recent findings.
It is difficult to directly observe the location and measure the three-dimensional structure of subsurface ice because of its sub-surface existence. At the local level, understanding of stratigraphic structure through samples obtained by core drilling is straightforward but limited in number and locations. Electrical sensing and ground-penetrating radar can estimate the spread and depth to some extent, however, extending such observations to a wide area is difficult. The estimation using remotely-sensed observations by airplanes and/or satellites has made great progress in recent years, but it does not directly identify the distribution of existence and reserves, but mainly calculates the volume of subsurface ice melting based on the depth of subsidence in the areas where the land surface was disturbed by wildfires, and indirectly estimates the overall distribution in the surrounding area in combination with topographical information.
There are only limited data available to understand the large-scale distribution and quantity of ground ice. The most widely used large-scale distribution data at present are distribution maps created at the end of the last century by combining geological and geomorphological information with outcrop and cross-sectional surveys in the field, provided at a resolution of 1 or 0.5 degrees latitude and longitude for the Northern Hemisphere. In addition, datasets that capture more detailed ground ice distribution in specific regions, such as the Canadian and Siberian regions, are being created by adding local field observations and geomorphological considerations.
Numerical model experiments and simulations have been conducted to estimate and understand the large-scale dynamics of ground ice. In particular, groundwater hydrology has begun to be implemented as a part of the subsurface hydrological conditions in parallel with the sub-surface temperature conditions, with the improvement and sophistication of global climate models in the 2000s. Since then, the carbon budget in the ecosystem (vegetation), hydrological dynamics and water balance, and the melting and decomposition of stored carbon are also attracting attention these days. The issues of these large-scale models are 1) the formation and loss of excess ice that surpasses the porosity, and its linkage with topographic changes in the vertical direction, 2) the handling of spatial heterogeneity in the horizontal direction, and 3) the identification and implementation of sub-grid side processes, which manifest the scale gap between the spatial scale of the phenomena and the model resolution.
Recently, the authors estimated the present-day distribution of ground ice and soil organic carbon at 2 km resolution by developing and employing a numerical model to estimate the respective temporal changes of ground ice and soil organic carbon in the Arctic Circle since the last interglacial. This presentation introduces ground ice distribution and variations from an Earth system perspective, including these recent findings.