Abstract
<p class="p1" style="margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; font-size: 12px; line-height: normal; font-family: "Helvetica Neue";">Sea-surface temperatures in the North Atlantic vary from decade-to-decade and those variations influence the weather of the surrounding continents. Prediction of these fluctuations may provide us foresight into temperature and precipitation in North America, Europe, and Africa. It may even help us plan for the number of Atlantic hurricanes. If we hope to predict the undulations of North Atlantic sea-surface temperatures, we need to understand what causes them. Right now, the potential causes are a source of debate. The two leading candidates are the large-scale ocean circulation and radiative external forcing. In this thesis, we argue that external forcing is the dominant source of multidecadal North Atlantic sea-surface temperature variability. As the main source of variability, external forcing is capable of obscuring existing natural modes of variability (Chapter 2) as well as creating and sustaining its own climate impacts (Chapter 3). Further, external forcing has guided the phasing of the North Atlantic sea-surface temperatures over the last millennium, making our interpretation of the modern Atlantic Multidecadal Variability (AMV) more plausible (Chapter 4). Finally, we demonstrate that the influence of external forcing is not limited to sea-surface temperature; forcing is the key source of predictive skill in atmospheric variability at these timescales as well (Chapter 5). We conclude by discussing the implications of our findings, the foremost of which is: sea-surface temperatures in the North Atlantic will continue to warm and we will continue to see those impacts associated with the warm phase of the AMV into the future.<span class="Apple-converted-space"> </span></p>