Research goals and objectives
In our project, we will target East Antarctica. Taking advantage of our foresight, we will combine in-situ monitoring with model research. We will also clarify the actual state, the elementary processes of their fluctuations and interactions of the Antarctic Bottom Water, Circumpolar Current, ecosystems, ice sheets, and the solid Earth in Antarctica and its surrounding areas. In particular, we aim to reconstruct the past of the Southern Ocean, Antarctic climate and ice sheet variability. We also aim to elucidate the interaction between the Antarctic ice sheet and ocean, and variability of ecosystem dynamics.
We will build an environmental system model of East Antarctica, which has been a missing piece. We will try to clarify a role of the Southern Ocean and the Antarctic ice sheet in the global environmental change and its mechanism through different interactions. Our research project is expected to have a ripple effect on many fields such as future projection of climate and social influence.The following items have important significance from an interdisciplinary perspective: (1) integration of simulation with a multi-level numerical model and in-situ monitoring data; (2) in-situ monitoring conducting beyond each field; and (3) development of unmanned exploration technologies.
On the basis of the results achieved in this project, we will also build a foundation for the development of international collaborative research starting from Japan by collaborating with other countries studying East Antarctica.
Summary of the research
Research item A01: The Southern Ocean as a reservoir of heat and materials and its variation
A01 consists of the following research plans: (1) A01-1 “Circulation dynamics of heat, freshwater, and material originating from Antarctic Bottom Water”; (2) A01-2 “Paleoclimate dynamics of the Southern Ocean”; and (3) A01-3 “Ecosystem dynamics in the Antarctic sea ice zone”.
From the viewpoint of the Southern Ocean as a reservoir of heat and materials, we will elucidate the interaction processes among the atmosphere, ice sheet, sea ice and ocean in the boundary areas of the sea ice and ice sheet, through the observation of physical oceanography, chemistry, biology, and geology. We will also clarify the variation of the ocean circulation, material cycles, and ecosystem dynamics from past to present.
A01-1 Circulation dynamics of heat, freshwater, and material originating from Antarctic Bottom Water
Targeting East Antarctica that has been a missing piece of abyssal circulation, we will quantify the formation, circulation, and variation of the Antarctic Bottom Water and the accompanying material cycles, including the influence of the melting ice shelves, based on in-situ observations. We will also evaluate the role of the interaction between the bottom water and ice sheets on the global heat, water, and material circulations.
Focusing on the Amery Ice Shelf area, we will quantify the formation, circulation, and variability of bottom water, including the influence of the melting ice shelves, in terms of several chemical tracers such as CFCs, SF6, δ18O, and mooring observations.
We will estimate the nutrient circulation and the CO2 uptake rate stemming from the bottom water through the measurements of total carbonate etc..
Further, we will evaluate their influence on climate and ecosystems, in collaboration with the ecosystem group.We will observe the process for high production of sea ice and dense water, and material cycles in the Cape Darnley polynya, where dense water and materials sink, by introducing the mooring of the automatic water samplers and profiling floats.
Targeting Amery Ice Shelf and Shirase Glacier, we will clarify the elementary processes of the interaction among the sea ice, ocean, and glaciers, using underwater robots and bio-logging technologies, in collaboration with the exploration group and the ice-sheet group.
A01-2 Paleoclimate dynamics of the Southern Ocean
We will reconstruct paleoceanographic variability of the Southern Ocean from the Pliocene epoch of five million years, through to the present day. We will elucidate the interaction between the dynamics of the Antarctic Circumpolar Current, Antarctic Bottom Water, sea ice, and global climate change.
- We will conduct an in-situ monitoring and collect samples in collaboration with the bottom water group. We will conduct sediment trap experiments in collaboration with the ecosystem group and clarify the seasonal variation of the sinking particles in the polar frontal zone and the seasonal ice zone. We will unravel the influence of sea-ice coverage on the biogeochemical processes, improve the accuracy of paleoceanographic proxies, and develop new ones.
- We will reconstruct the variations of surface water temperature, salinity, nutrient salt, winter sea- ice distribution, dust input, and biological pump using deep-sea sediment cores in the Southern Ocean. We will also clarify the process of shifting from the glacial period to the warm period and the dynamics of the Southern Ocean variability over the glacial-interglacial cycles in collaboration with the ice sheet group.
- We will elucidate the interaction of the ocean circulation, sea-ice distribution changes in the Southern Ocean, the Antarctic ice sheet, sea level, and global climate change from the Pliocene warm period through the quarterly period, when the earth cooled, and in the super warm period. We will conduct this project in collaboration with the solid earth group and the modelling group.
A01-3 Ecosystem dynamics in the Antarctic sea ice zone
Using “Umitaka-Maru”, a training and research vessel of Tokyo University of Marine Science and Technology, we will try to understand the ecosystem structure and its dynamics that drive material cycles of carbon in the seasonal ice zone; therefore, we will try to evaluate the influence of sea-ice variability on the marine ecosystem and the material circulation in East Antarctica.
- Ecosystem and material circulation of surface seawater: We will focus on dynamics, life, and reproductive mechanisms of the biotic communities, plants, zooplanktons, and small fish beneath the ice and in the marginal ice zone from the melting period through the production period of sea ice. We will clarify the material circulation in the surface layer. We will conduct research in collaboration with the bottom water group and the paleoceanography group.
- Vertical transportation by biological pump: We will conduct time-series observations throughout the year including winter season by means of autonomous observation systems such as mooring and drifting systems. However, conducting research by vessels may be difficult during winter season. We will clarify the process of transporting and isolating materials fixed by biotic communities from the surface layer to the deep layer. We will conduct this project in collaboration with the paleoceanography group.
- Movement of top predators and materials: We will investigate the response process of sea birds and large mammals to ecosystem change in the seasonal ice zone and quantify the influence of predators on the material circulation.
Research item A02: Reservoirs of waterand heat, the Antarctic ice sheet and its variation
A02 consists of A02-1 “Variation and interaction of the Antarctic ice sheet and climate” and A02-2 “Interaction between the solid Earth and the Antarctic ice sheet”.
From the viewpoint of the Antarctic ice sheet as water and heat reservoir, we will conduct geodetic, geophysical and glaciological observe to reveal the flow of ice sheets, surface mass balance. We will also analyze ice cores with the aim of elucidating the relation between the characteristics of the Antarctic climate as the CO2 reservoir and the global changes over the past several million years to the present day. In addition, we aim at revealing the response of solid Earth related to the Antarctic ice sheet changes as well.
A02-1 Variations and interactions of climate and the Antarctic Ice Sheet
We analyze ice cores, and perform in-situ and satellite observations to investigate the past and present of the Antarctic Ice Sheet and global climate. The goal of our study is to better understand the mechanisms driving the variations and interactions of the ice sheet and climate. We focus on the reconstruction of temperature, snow accumulation, sea ice, and carbon cycles over the past several hundred thousand years, as well as the observations of the ice sheet mass balance and ice sheet-ocean interaction.
- We analyze ice cores drilled at Dome Fuji to reconstruct Antarctic and global environmental changes. The focuses of the analysis are: (1) carbon dioxide concentration as the input of ice sheets and climate models, (2) water isotopes and noble gas for the reconstruction of temperature and seawater temperature, (3) aerosols related to the radiative forcing and material circulation, (4) sea-ice derived materials (5) methane concentration for the reconstruction of climate instability, (6) air content as an indicator of ice sheet elevation change, and (7) various components for more accurate dating. FWith a special focus on the “super warm period”, when the Antarctic Ice Sheet receded, we perform a comparative study using numerical models and deep sea cores in collaboration with the paleoceanography and the modelling group. We also study the formation process of paleoenvironmental signals.
- We measure the flow speed and mass change of the ice sheet based on in-situ observations and remote sensing techniques. Mass balance and ice loss are quantified in coastal areas as well as over an entire drainage basin to understand the mechanism of glacier acceleration, ice-shelf basal melting, and grounding line migration in collaboration with the bottom water and the solid earth research groups. In collaboration with the modelling group, we contribute to the refinement of ice sheet models, and more accurate future projection of the ice sheet volume and sea level rise.
A02-2 Interaction of the solid Earth and the Antarctic Ice Sheet
We will improve the accuracy of the Glacial Isostatic Adjustment (GIA) model, which is the response of the solid Earth associated with the ice sheet mass changes. We will also reveal the ice sheet mass balance from past to present, by conducting geodetic, geomorphological, geological, and sea bottom geomorphological surveys in the coastal areas and the inland mountain areas of East Antarctica. Consequently we will contribute to the studies for integrating ice sheet, ocean, and climate models.
- Based on the absolute gravity measurements and the GNSS measurements at several research stations and unexplored inland areas in East Antarctica, we will draw precise images of the current ice sheet variations and crustal movements. We will also reconstruct the past Antarctic ice-sheet variations based on topographic and geological surveys. ( collaboration with the ice-sheet group)
- We will try to improve the accuracy of the GIA model by combining in-situ geodetic data and satellite data such as InSAR, GRACE, and altimeter data. ( collaboration with the ice-sheet group and the modelling group)
- Based on the analysis of micro glacial landforms and sea bottom topography observed by detailed aerial surveys using unmanned aerial vehicles and other new observation techniques, we will try to improve the accuracy in the reconstruction of the retreat process of ice sheets, and to enhance the accuracy of GIA analysis consequently. ( collaboration with the exploration group)
- Using the improved GIA model with high precision, we will precisely reconstruct the ice sheet melting history over the past million years and after the last glacial period in East Antarctica. Ultimately we will try to clarify the response mechanism of the East Antarctic ice sheet to the global climate change and its variation speed as well. (collaboration with the modelling group)
Research item A03: Challenges for unexplored frontiers
We will acquire observation data that may bring a breakthrough in our studies using new observation devices in unexplored areas. In particular, we aim to obtain data of temperature, salinity, and topographic features using unmanned aerial vehicles and a year-round observation device beneath the sea ice.
Using unmanned aerial vehicles over the ices and rocks will allow us to make a large-area mapping of the shapes and landforms of glaciers. We will introduce new methods of research observation across different fields to enhance coordination with each research group.
A03 Challenges for unexplored frontiers
With the introduction of unmanned aerial vehicles such as underwater robots (AUVs), we will try to elucidate unexplored areas of the Antarctic ocean, such as the structure of sea ice, ice shelves and along the marginal ice zone and seabed. We also aim to measure a three-dimensional surface shape of the Antarctic sea ice, glaciers, and land areas in high resolution using unmanned aerial vehicles.
We will make a breakthrough in the studies of ice sheets and the ocean besides our project by using data obtainable.
- Introduction of a floating and sinking type water salinity meter will enable us to conduct a continuous observation beneath the sea ice. We will also develop technologies to conduct three-dimensional observations over a large area, in planar and vertical directions beneath the sea ice and ice shelves using autonomous underwater vehicles (AUVs). Introduction of the unmanned and underwater robots will enable us to conduct conventional observations in unexplored areas. We will also promote our research for the elucidation of the influx of freshwater from the Antarctic ice of land origin, the sea bottom topography that records ice sheet history, and dynamics of the abyssal circulation of the ocean beneath the sea ice. We will conduct this research project in collaboration with the bottom water group, the solid earth group, and the modelling group.
- We will construct stable flight technology of unmanned aerial vehicles in the polar region, fly them automatically with a small laser scanner, and create three-dimensional, surface shape data of sea ice, glaciers, exposed rocks, and inland mountains in the margin of the Antarctic Ice Shelf with high accuracy and high resolution. We will conduct this research project in collaboration with the ice sheet group and the solid earth group.
Research item A04: Integrative modeling of the Antarctic Ice Sheet, ocean, and climate
We aim to develop models of Ice Sheet- Ocean interactions and analyze variability of the Southern Ocean, material circulation, and variation factors of the Antarctic climate by numerical experiments.
We will develop models and conduct several numerical experiments independently. At the same time, we will promote integrated research by combining in-situ observations and experiments in A01 and A2 by providing feedback about our result.
A 04 Integrative modeling of the Antarctic Ice Sheet, ocean, and climate
We will develop numerical experiments on variations in the Antarctic ice sheet, the ocean, climate, and material circulation at the various time scales by incorporating the latest findings from observations by other research groups into each modeling method accumulated.
We will try to understand the interaction between the Antarctic and global environmental changes, and the “tipping point”, which is a critical threshold when a transition to a new state occurs in the Antarctic ice sheet.
- Analysis of the Antarctic ice sheet and the ocean variability: We will build a model that can calculate the interaction between the ice sheet, the ocean, and the solid Earth. We will analyze factors on the observational evidence through integrated research on observations and models. We will conduct this research project in collaboration with the bottom water group, the ecosystem group, the ice sheet group, the solid earth group, and the exploration group.
- Integrated research on climate modeling and data over the past few million years, including a “very warm period”: Using survey data on ice cores, deep-sea cores, and topography for the input and verification, we will conduct modeling studies of the material circulation such as the ice sheet, the ocean, sea ice, carbon, and water isotopes. We will also analyze their variation mechanisms in collaboration with the paleoceanography group, the ice sheet group, and the solid earth group.
- Understanding of the tipping points and future predictions: Using the results of models and data, we will clarify the condition and mechanism when the Antarctic ice sheet and the bottom water formation pass a tipping point. We will also plan for the future research. We will conduct this project in collaboration with the bottom water group, the paleoceanography group, the ecosystem group, the ice sheet group, and the solid earth group.