Atlantic Ocean's Thermohaline Circulation
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"The Mass balance and freshwater contribution of the Greenland ice sheet: a combined modelling and observational approach" project, which was a Natural Environment Research Council (NERC) RAPID Climate Change Research Programme project (Joint International Round - NE/C51631X/1 - Duration 1 Jun 2005 - 30 Nov 2008) led Prof Jonathan Bamber of the University of Bristol, with co-investigators at the Nansen Environmental & Remote Sensing Center, Norway, the Royal Netherlands Meteorology Institute and Dr MR van den Broeke, University of Utrecht, Netherlands. The dataset quantifies how, where and when the Greenland ice sheet has fed fresh water through iceberg calving, subglacial melting and meltwater runoff into the surrounding ocean during the last half century. This dataset collection contains precipitation, evaporation and run off model outputs. The thermohaline circulation is a global ocean circulation, driven by differences in the density of the sea water that is controlled by temperature (thermal) and salinity (haline). In the north Atlantic, the thermohaline circulation transports warm and salty water to the north, where it, together with the North Atlantic Drift (the north-eastern most extension of the Gulfstream), contributes to the warm sea surface along the coast of western Europe and to the relatively mild European winters. From ice cores drilled in Greenland, there is evidence that rapid climate changes took place during the last glacial (the period roughly from 100,000 to 20,000 years before present): over a period of just several decades, northern European winter temperature dropped by as much as 10 degrees for periods typically lasting 1000 years. The present explanation is that large, pulse-like freshwater fluxes (probably from icebergs that originated from the continental ice sheets) were released into the north Atlantic where they weakened or shut down the thermohaline circulation. In a warmer greenhouse climate, it is also likely that the freshwater flux into the north Atlantic will increase; using a scenario of doubling CO2 within the next 70 years, most atmospheric models predict an increase in precipitation in high latitudes. One of the great uncertainties in these projections is the role of the Greenland ice sheet, which is situated in the middle of the area of interest. We know so little about the variability in its meltwater production and its sensitivity to regional warming that its contribution to the problem of the north Atlantic thermohaline circulation is often ignored, in spite of the fact that the Greenland ice sheet contains enough water to rise global sea level by 6 m! In this proposed research we quantifyed in detail how, where and when the Greenland ice sheet has fed fresh water through iceberg calving, subglacial melting and meltwater runoff into the surrounding ocean during the last half century. The melting and runoff was calculated using a coupled snow - atmosphere model that is run over Greenland at very high resolution (11 km in the horizontal), which took about 1 year on a supercomputer to run! Rapid Climate Change (RAPID) was a £20 million, six-year (2001-2007) programme for the Natural Environment Research Council. The programme aimed to improve the ability to quantify the probability and magnitude of future rapid change in climate, with a main (but not exclusive) focus on the role of the Atlantic Ocean's Thermohaline Circulation.
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This collection contains data from "The Quantitative applications of high-resolution late Holocene proxy data sets: estimating climate sensitivity and thermohaline circulation influences" project, which was a Natural Environment Research Council (NERC) RAPID Climate Change Research Programme project (Round 1 - NER/T/S/2002/00440 - Duration 1 Jul 2003 - 30 Jun 2008) led by Prof Keith Briffa of the University of East Anglia, with co-investigators at the University of East Anglia. This dataset collection contains self-calibrating Palmer Drought Severity Index data. This project analysed the output from state-of-the-art coupled climate models in conjunction with very long instrumental climate data and an extensive archive of annual- and selected decadal-resolution palaeoclimate data to study climate changes during the past millennium. Actual and model-derived synthetic networks of palaeoclimate data have been used to estimate the extent to which (i) variations in Atlantic meridional overturning circulation strength; (ii) variations in the North Atlantic Oscillation; and (iii) the sensitivity of climate to external forcing changes can be reconstructed from different networks of palaeoclimate data, making assumptions about coverage, seasonality of response and reliability of expressed climate signal.
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Data from "The Predictability of rapid climate change associated with the Atlantic thermohaline circulation" project. This was a Natural Environment Research Council (NERC) RAPID Climate Change Research Programme project (Round 2 - NE/C509174/1 - Duration 1 Jan 2005 - 18 Sep 2008) led by Prof Rowan Sutton of the University of Reading, with co-investigators at the University of Oxford and at the National Oceanography Centre. The dataset identifies the dominant sources of uncertainty in General Circulation Model predictions of the Thermohaline Circulation. This dataset contains meteorology model output from the HadCM3 control ensemble. Forecasts of the future behaviour of the Atlantic Thermohaline Circulation (THC) are needed to inform policy on climate change. Such forecasts must be probabilistic taking into account the principal sources of uncertainty. It is not possible to sample exhaustively all sources of uncertainty because the number of degrees of freedom is too great. Consequently a future forecasting system will be reliant on strategies to identify those dimensions of uncertainty that are most important. This project developed an objective methodology to identify the dominant sources of uncertainty in General Circulation Model predictions of the THC. Perturbations to oceanic initial conditions and climate model parameters that generate the most rapid change in the THC and related aspects of climate were identified. These perturbations were used to produce an early probabilistic forecast for the behaviour of the THC up to 2100. The results were also feed directly into the next generation of ensemble climate predictions being developed at the UK Hadley Centre. Rapid Climate Change (RAPID) was a £20 million, six-year (2001-2007) programme for the Natural Environment Research Council. The programme aimed to improve the ability to quantify the probability and magnitude of future rapid change in climate, with a main (but not exclusive) focus on the role of the Atlantic Ocean's Thermohaline Circulation.
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The main tools that are used for making projections of climate change in the coming century resulting from greenhouse-gas and other emissions are detailed coupled three-dimensional models of the atmosphere and ocean. However, such models give widely different results for some important aspects of climate change, thus limiting our ability to make practically useful projections. One such aspect is changes that may happen in the Atlantic Ocean thermohaline circulation, often referred to as the Gulf Stream. This circulation transports a great deal of heat northwards. If it weakened, future warming in Europe in particular could be reduced or possibly reversed. The spread of model results basically reflects limitations in current understanding of how the large-scale climate system operates. The aim of this project was to identify which are the most important aspects of that uncertainty by making comparisons of the responses simulated by a range of climate models. The results were intended to help improve the models by focusing attention on the aspects which require further theoretical or observational study. This dataset collection contains meteorology and ocean model outputs. Rapid Climate Change (RAPID) was a £20 million, six-year (2001-2007) programme for the Natural Environment Research Council. The programme aimed to improve the ability to quantify the probability and magnitude of future rapid change in climate, with a main (but not exclusive) focus on the role of the Atlantic Ocean's Thermohaline Circulation.
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"The Assimilation in ocean and coupled models to determine the thermohaline circulation" project was a Natural Environment Research Council (NERC) RAPID Climate Change Research Programme project (Round 2 - NE/C509058/1 - Duration 1 Sep 2005 - 30 Sep 2009) led by Prof Keith Haines of the University of Reading, with co-investigators at the National Oceanography Centre. This dataset collection contains Atlantic Ocean Thermohaline Circulation (ATOC) model measurements. To make the best use of the historical research ship records as well as new observations from autonomous ocean profiling floats and special observing programs such as Rapid climate change, it was proposed to assimilate all of the available data from the past 40 years into a high quality ocean circulation model that can represent complete fields of ocean properties. In this way derived quantities such as the north-south mass and heat transports which are vital to understanding the oceans role in controlling climate, could be determined. The project also put into context the various timeseries of observations that have been compiled from local regions which suggest that important changes in ocean circulation and transports have been ongoing in the past decades. These timeseries have been put into a basin scale and global scale context of ongoing change. The program determined the relationship between hydrographic signals in different parts of the ocean basins (particularly the N Atlantic). The program provided a method for assimilating data from the thermohaline monitoring arrays into an ocean model that could then be used as part of a coupled climate model for multi-annual climate prediction. Rapid Climate Change (RAPID) was a £20 million, six-year (2001-2007) programme for the Natural Environment Research Council. The programme aimed to improve the ability to quantify the probability and magnitude of future rapid change in climate, with a main (but not exclusive) focus on the role of the Atlantic Ocean's Thermohaline Circulation.
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"To what extent was the Little Ice Age a result of a change in the thermohaline circulation?" project. This was a Natural Environment Research Council (NERC) RAPID Climate Change Research Programme project (Joint International Round - NE/C509507/1 - Duration 1 Aug 2005 - 31 Jul 2008) led by Dr Tim Osborn of the University of East Anglia, with co-investigators at the University of East Anglia and Royal Netherlands Meteorology Institute. The dataset contains positive North Atlantic Oscillation model output from the HadCM3 model.
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The Assimilation in ocean and coupled models to determine the thermohaline circulation" project was a Natural Environment Research Council (NERC) RAPID Climate Change Research Programme project (Round 2 - NE/C509058/1 - Duration 1 Sep 2005 - 30 Sep 2009) led by Prof Keith Haines of the University of Reading, with co-investigators at the National Oceanography Centre. This dataset collection contains Atlantic Ocean Thermohaline Circulation ORCA025 model output.
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"Improving our ability to predict rapid changes in the El Nino Southern Oscillation climatic phenomenon" project, which was a Natural Environment Research Council (NERC) RAPID Climate Change Research Programme project (Round 1 - NER/T/S/2002/00443 - Duration 1 Jan 2004 - 30 Sep 2007) led by Prof Alexander Tudhope of the University of Edinburgh, with co-investigators at the Scottish Universities Environment Research Centre, Bigelow Laboratory for Ocean Sciences, and the University of Reading. This dataset collection contains meteorology and ocean model outputs from the Hadley Centre Coupled Model, version 3 (HadCM3) model. The objective was to use a combination of palaeoclimate reconstruction from annually-banded corals and the fully coupled HadCM3 atmosphere-ocean general circulation model to develop an understanding of the controls on variability in the strength and frequency of ENSO, and to improve our ability to predict the likelihood of future rapid changes in this important element of the climate system. To achieve this, we targeted three periods:0-2.5 ka: Representative of near-modern climate forcing; revealing the internal variability in the system.6-9 ka: a period of weak or absent ENSO, and different orbital forcing; a test of the model's ability to capture externally-forced change in ENSO.200-2100 AD: by using the palaeo periods to test and optimise model parameterisation, produce a new, improved, prediction of ENSO variability in a warming world. Rapid Climate Change (RAPID) was a £20 million, six-year (2001-2007) programme for the Natural Environment Research Council. The programme aimed to improve the ability to quantify the probability and magnitude of future rapid change in climate, with a main (but not exclusive) focus on the role of the Atlantic Ocean's Thermohaline Circulation.
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"Improving our ability to predict rapid changes in the El Nino Southern Oscillation climatic phenomenon" project, which was a Natural Environment Research Council (NERC) RAPID Climate Change Research Programme project (Round 1 - NER/T/S/2002/00443 - Duration 1 Jan 2004 - 30 Sep 2007) led by Prof Alexander Tudhope of the University of Edinburgh, with co-investigators at the Scottish Universities Environment Research Centre, Bigelow Laboratory for Ocean Sciences, and the University of Reading. This dataset collection contains meteorology and ocean model outputs from the FORTE2 model. The objective was to use a combination of palaeoclimate reconstruction from annually-banded corals and the fully coupled HadCM3 atmosphere-ocean general circulation model to develop an understanding of the controls on variability in the strength and frequency of ENSO, and to improve our ability to predict the likelihood of future rapid changes in this important element of the climate system. To achieve this, we targeted three periods:0-2.5 ka: Representative of near-modern climate forcing; revealing the internal variability in the system.6-9 ka: a period of weak or absent ENSO, and different orbital forcing; a test of the model's ability to capture externally-forced change in ENSO.200-2100 AD: by using the palaeo periods to test and optimise model parameterisation, produce a new, improved, prediction of ENSO variability in a warming world. Rapid Climate Change (RAPID) was a £20 million, six-year (2001-2007) programme for the Natural Environment Research Council. The programme aimed to improve the ability to quantify the probability and magnitude of future rapid change in climate, with a main (but not exclusive) focus on the role of the Atlantic Ocean's Thermohaline Circulation.
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"To what extent was the Little Ice Age a result of a change in the thermohaline circulation?" project. This was a Natural Environment Research Council (NERC) RAPID Climate Change Research Programme project (Joint International Round - NE/C509507/1 - Duration 1 Aug 2005 - 31 Jul 2008) led by Dr Tim Osborn of the University of East Anglia, with co-investigators at the University of East Anglia and Royal Netherlands Meteorology Institute. The dataset contains radiative forcing model output from the HadCM3 model.