The ocean as part of the climate system
Topic "MAR" of the research programme "MARCOPOLI"
The climate on Earth and its variability are largely controlled by interactions between ocean and atmosphere. For this reason, both are given high priority on the international climate agenda.
Ocean currents play the lead role in governing climate and weather conditions: apart from atmospheric circulation, they are the major factor in global temperature exchange. The reason is the oceans’ colossal size: 71 percent of the earth’s surface is covered by ocean water. Especially within the surface layers, the sun’s irradiation energy is transformed into thermal energy. The large specific heat capacity of water makes the ocean act as a buffer to seasonal temperature changes in the atmosphere. Thus, ocean and atmosphere contribute more or less equally to regulating energy transport of irradiation energy on Earth, providing the very essentials for life at higher latitudes.
The ocean is subject to a powerful system of currents which transport immense amounts of energy across large distances; mostly from the regions of highest irradiance on either side of the equator towards the North and South Poles. In addition, the ocean current system represents a dynamic link between polar and warm regions which may change over decades or longer time periods: Over short time intervals, ocean and atmosphere are controlling climate fluctuations on the planet, with atmospheric effects being dominant. In contrast, on larger time scales, i.e. hundreds or thousands of years, it is the ocean influencing the dynamics of the climate system. Also, over long time periods the polar ice comes into play: it increases and decreases in relation to the oceanic transport of heat and water, and with the discharge of earth and ocean lithosphere.
Moreover, the marine circulation adapts to tectonic modifications and continental geometry: as marine passages are opening or closing with tectonic movements, the water finds new pathways for the transport of heat, as well as dissolved and particulate matter. The marine biomass always responds to the given environmental conditions: at any one time, alterations in the abundance and composition of its isotopes reflect the predominant climate and indicate its change. Shells and other organismal remains are deposited in sediments and preserve the climate history of millions of years. If its species, geochemistry and isotope composition are known, they can be related to physical alterations of the climate.
Extensive knowledge of ocean dynamics and its impact on the global climate system is crucial for understanding and evaluating changes and dynamics of climate. Therefore, the programme TopicMAR combines two project units (‘ocean and global climate’) in order to explore the ocean’s role in the global climate process. Topic MAR is part of the research programme MARCOPOLI, which, in addition, investigates coasts (Topic CO) and polar regions of Arctic and Antarctic (Topic POL). The following goals are incorporated into the research and development programme Topic MAR:
Establishment of data and models of varying complexity
The global data base on climate has seen a tremendous increase in volume through satellite technology and large-scale international research programmes. Until very recently, data-oriented modelling represented a novel approach. However, nowadays our advanced understanding of processes and the ongoing expansions of computer capacities have allowed us to build climate models of much higher complexity.
The Alfred Wegener Institute for Polar and Marine Research combines existing research tools with observations and simulation models. They are accompanied by theoretical models, consisting of processes and subsystems. Obtaining a comprehensive overview of climate fluctuations and their causes is the overarching goal of the investigations.
Building bridges between physical and biological sciences
The integration of various scientific disciplines into climate research has already been incorporated into several significant international research programmes. Interactions of physical and biological subsystems are manifested, in particular, in the ocean, where transport and mixing already represent components of biological processes. Furthermore, biological micro-organisms are strongly influenced by the physical environment. Therefore, scientists at the Alfred Wegener Institute for Polar and Marine Research use a holistic approach to investigating physical and biological systems.
Models of marine biogeochemistry and the role of organisms
One of the primary research topics is the ocean’s biogeochemistry, explored through a gradual understanding. Identifying the dominant organisms and modelling their role within the biogeochemical cycle, represents an additional goal.
Reconstruction of the global climate since the Cenozoic (65 million years ago)
The search for the dominant climate-altering mechanisms during this era reveals a transition of glacial and interglacial events which, for this reason, are central to climate research. The enormous and rapid climate fluctuations of the latest glacial period are currently being investigated using new sediments and archived ice cores. Dynamic mathematical systems explore dynamic climate equilibriums. For this purpose, the Alfred Wegener Institute has produced a hierarchy of models with varying complexity, using climate archives and proxy models.
Research plan and network
Research under the Topic MAR project takes place largely at the Alfred Wegener Institute for Polar and Marine Research. GKSS-contributions are limited to the related work package Topic MAR 2. Arrangement of the work packages is based on the predominant time scales related to atmosphere, ocean, sea ice, ice cover and sediments.