Climate change is one of the most urgent issues facing humanity and life on Earth. Better predictions of future climate change are needed, so that measures to reduce its impact and cope with its effects can be put in place. However, improving these predictions requires better knowledge of how the global climate system functions, and this knowledge is currently incomplete. A critical gap concerns understanding of the uptake of heat and carbon by the oceans. Over 90% of the extra heat now present in the Earth System because of global warming has entered the ocean, with strong increases in both the upper and deep ocean apparent since the 1970s. Further, the global ocean is the largest reservoir of carbon in the climate system, and has absorbed nearly one-third of the extra carbon emissions produced since the industrial revolution. Climate change in the atmosphere is strongly moderated by these processes, and would be dramatically greater without them. The Southern Ocean - the vast ocean that encircles Antarctica - is critically important in this regard. Because of the nature of its circulation, its physical and chemical properties, and its connections with the rest of the globe, it accounts for around half of the oceanic uptake of carbon, and around three-quarters of the heat uptake. However, because of its remoteness and hostile environment, with stormy seas, heavy sea ice in places, and long periods of darkness in winter, the Southern Ocean is also the least-measured and least-understood ocean in the world. One consequence of this lack of understanding is that the representations of the Southern Ocean in many of the models used to create future climate projections are not fit for purpose. Our project, ENCORE is the National Capability ORchestra Extension (ENCORE) extends the original Ocean Regulation of Climate by Heat and Carbon Sequestration and Transports (ORCHESTRA) by a year. It represents a linking together of many of the major environmental research institutes in the UK, who will work with national and international partners to address these issues. We will carry on our unique combination of data collection, novel analyses and computer simulations to radically improve our ability to measure, understand and predict the circulation and role in global climate of the Southern Ocean. In the single field season available to us data collection will include three cruise elements continuing our long term monitoring of the Atlantic sector of the Southern Ocean to determine the basin-scale transports of heat and carbon in all the different ocean layers (near-surface, intermediate, abyssal). It will also carry on flights with research aircraft to determine climatically-important transfers of heat and carbon between the atmosphere and ocean in all different conditions of sea ice. Information gathered by previous such field work will continue to be examined, producing new insights into ocean processes and improvements to ocean models. An important element of ENCORE will be the synthesis of the new information and understanding gathered over the ORCHESTRA period both with itself and with complimentary parallel projects such as RoSES, SOCCOM and SO-CHIC. This synthesis will produce a holistic understanding of the Atlantic sector and wider Southern Ocean's impact on global climate, and how it may change in the future. ENCORE will work closely with the Met Office in particular to see that such understanding is pulled through to examine the ability of the HadGEM and other UK climate models to replicate the complex dynamics of the region, and to suggest improvements to future iterations of these models.