Since changes in the Antarctic environment have a considerable impact on global environmental changes, understanding these changes in Antarctica is key to predicting future changes in the global environment. Antarctica was previously considered to be stable, however, recent observations have shown that the Antarctic ice sheet is undergoing changes, including melting of the Western Antarctic ice sheet. In the event that the rate of these changes accelerates rapidly, some experts warn that a “tipping point of no return” could be reached by the middle of this century.
However, different models have produced markedly different outcomes regarding how long it will take to reach this tipping point, and the impact that this will have on the global environment. Scientists still do not fully understand the process of melting of the Antarctic ice sheet during warm periods in the past, the process of melting by the ocean, and how the balance between melting and snowfall affects the mass of the ice sheet. This has led to the differences in predicted outcomes. Currently, there is a significant lack of observational data to constrain these models adequately.
The Japanese Antarctic Research Project Phase X Six-Year Plan identifies “Inferring the future global environment system by investigating the past and present of Antarctica” as the main theme for Prioritized Research Projects. It includes three sub-themes focusing on the Antarctic ice sheet, ocean circulation, and atmospheric circulation. Since these elements are particularly important as constraints for future prediction models, we will conduct intensive research with the aim of understanding past and present changes and identifying the mechanisms behind these changes.
Field research, satellite observations, and numerical modelling have shown that the Antarctic ice sheet and the Greenland ice sheet have been losing mass at an accelerating rate over the past few decades. Despite these findings, considerable uncertainties remain on their causes and future outlook. In order to better understand the mechanisms underlying the changes in the climate-ice sheet system and to improve the accuracy of future projections, reconstructing paleo-environmental conditions is important, not only for the current 100,000-year glacial-interglacial cycles, but also for the transition from 40,000-year to 100,000-year cycles, which is believed to have occurred approximately 1 million years ago. The reconstructions will provide better constraints on the boundary conditions for numerical models and help verify their results.
Through the drilling and analysis of the first and second Dome Fuji deep ice cores, we have reconstructed Antarctic and global environmental changes over the past 720,000 years, revealing the nature and mechanisms of the 100,000-year glacial-interglacial cycles. However, while various hypotheses have been proposed for the transition from the 40,000-year to 100,000-year cycles that occurred about a million years ago, it remains poorly understood due to a lack of data. The International Partnership in Ice Core Sciences (IPICS), a research framework focusing on ice core studies, initiated the “Oldest Ice” project with the aim of collecting multiple Antarctic ice cores that extend beyond 1 million years in age. Under this international framework, several countries have been conducting surveys to identify suitable drilling sites. In the JARE Phase IX Six-Year Plan, Japan conducted large-scale, high-precision radar surveys and other glaciological studies to narrow down the optimal site for the oldest ice core drilling around Dome Fuji. In Phase X, based on these findings, we will attempt to extract an “oldest ice core” exceeding 1 million years.
Additionally, in conjunction with Sub-theme 2, we will conduct marine sediment drilling from the icebreaker Shirase along the East Antarctic coast and carry out seafloor bathymetry surveys. The geological drilling system developed in Phase IX will be used for land and lake sediment drilling, and we will also conduct glacial geomorphological surveys. Furthermore, we will collaborate with international sediment drilling projects that cover a broad area, including beneath the ice shelf, to collect geological samples and data on past ice sheet changes.
By collecting samples from East Antarctica and conducting measurements on them, performing data analyses, and engaging in climate-ice sheet modeling through various collaborations with external institutions, we will develop a comprehensive understanding of how the ice sheet, atmosphere, and oceans have evolved from the past to the present. The project will help improve future projections of global environmental changes by enhancing our understanding of the complex interactions between Antarctica and the global climate system, as well as the mechanisms driving these changes.
The Antarctic ice sheet, a vast mass of ice, could raise global sea levels by up to 60 meters if it melted entirely. Clarifying the process of mass loss due to melting of the Antarctic ice sheet and how it will respond to future global warming is an urgent task for predicting future rises in sea level. The glaciers and ice sheet of East Antarctica, where the Japanese Antarctic Research Expedition (JARE) has focused its observations, were believed to be more stable than those in West Antarctica. However, recent years have seen an acceleration in melt rates from ice shelves at the fronts of Totten Glacier and other glaciers, which is considered to be due to the inflow of warm water from the ocean basin towards the continental shelf. Mass loss from glaciers and ice sheets causes fresh water to be released into the ocean, which not only affects the formation of sea ice and Antarctic Bottom Water, but also changes in the marine ecosystem and biogeochemical cycles.
In the Japanese Antarctic Research Project Phase X Six-Year Plan, we will focus on the interactions between ice sheets, sea ice, and the ocean, all of which are directly linked to changes in sea level. We will conduct integrated research and observations across multiple fields, aiming to become the first country to clarify details of the mass loss process of the East Antarctic ice sheet, mainly in the Totten Glacier region, and the impact of this on the marine environment and biogeochemical cycles. The Totten Glacier, Vincennes Bay (Wilkes Land Coast) and Lützow-Holmbukta Bay have been identified as areas of East Antarctica with significant ice sheet-sea ice-ocean interaction. In these areas, we will conduct direct observations on the glacier in addition to oceanographic observations from the Japanese icebreaker Shirase. In addition to conducting standard CTD/RMS observations (i.e., measurements of water temperature, salinity and pressure, and water sampling), we will also conduct moored and drifting observations, under-ice observations using the autonomous underwater vehicle, on-board atmospheric observations, seafloor sediment drilling, on-board culture experiments, and other experiments. These observations will be conducted with a view to identifying the mechanisms underlying the movement of warm water from the ocean basin to the coastal margins of the ice sheet and its impact on subshelf melting; changes in the ice shelf, grounding line, and outlet glacier systems; reconstruction of past warm-water inflows; changes in ecosystems and biogeochemical cycles in seasonal sea ice areas and how these are affected by ocean and sea ice circulation; and cloud formation process and how these affect the reproducibility of the air-sea coupled system by climate models. Thus, while focusing on the rate of mass loss from the East Antarctic ice sheet and identifying how this affects the marine environment and the biogeochemical cycles, our research will also contribute to the study and observation of atmospheric changes, ice sheet dynamics, and the reconstruction of paleo-environmental information. These efforts are closely related to Sub-themes 1 and 3, aiming for an integrated understanding of ice sheet-sea ice-ocean interactions. This approach will help to improve climate models, leading to more accurate future predictions about global environmental changes, including sea level changes.
Antarctica plays a key role in the global climate, and is an important site for observing clear evidence of climate change. One of the main factors driving climate change is the alteration of atmospheric circulation, which is affected by a variety of atmospheric phenomena. The main objective of this sub-theme is to conduct comprehensive research in Antarctica, where there has been a lack of observations, to develop a quantitative understanding of these changes. As we discovered in Phase IX, other important factors in the formation of, maintenance of, and changes in Antarctic atmospheric circulation include the effects of energy inflow from the near-space environment to the middle and upper atmosphere of Antarctica, as well as interactions among ice sheets, oceans and atmosphere. It is vital to include these factors in our research into changes in atmospheric circulation.
In the Japanese Antarctic Research Project Phase X Six-Year Plan, we will continue to conduct multi-faceted atmospheric observations and international collaborations, mainly using the large-scale atmospheric radar called PANSY radar (Program of the Antarctic Syowa MST/IS Radar) at Syowa Station in Antarctica. We will capture Antarctic atmospheric phenomena over various spatiotemporal scales, ranging from a few minutes to an 11-year solar cycle. Each atmospheric phenomenon will be explored in terms of climatology, interannual changes, and characteristics of extreme events over a wide range of altitudes from the troposphere to the stratosphere and mesosphere. We will also look at atmospheric turbulence generated by various atmospheric phenomena in Antarctica, aiming to quantitatively evaluate the role of this atmospheric turbulence in transporting materials through atmospheric mixing. In the Antarctic stratosphere and troposphere, the circulation of materials moves both toward the pole and in a vertically downward direction. Clarifying this vigorous meteorological activity will advance our understanding of the flow of water vapor and other substances from the atmosphere to the cryosphere, which relates to Sub-themes 1 and 2. In addition to precise observations from Syowa Station and other observation points, we will conduct seasonal observation campaigns using balloons that facilitate comprehensive data collection across the whole of Antarctica. To evaluate the effects of the near-space environment on the Earth’s atmosphere, we will attempt to conduct observations of the ionosphere, which is located even higher than the mesosphere, and to expand networks for auroral imaging and cosmic ray observations at higher latitudes within the largely unobserved polar cap region.
In addition to these observations, by combining data assimilation research and high-resolution atmospheric circulation models that have already been developed in Japan, we aim to identify global interannual changes in atmospheric phenomena and the mechanisms underlying these variations, as well as the physical mechanisms of space weather phenomena. These findings will further improve the accuracy of future predictions about global environmental changes. We will also establish a shared-use system for the PANSY radar, perform observations in Antarctica based on proposals from the research community, and conduct research in response to diverse scientific requirements.