Recent multivariate changes in the North Atlantic climate system, with a focus on 2005–2016

Robson, Jon and Sutton, Rowan T. and Archibald, Alex and Cooper, Fenwick and Christensen, Matthew and Gray, Lesley J. and Holliday, N. Penny and Macintosh, Claire and McMillan, Malcolm and Moat, Ben and Russo, Maria and Tilling, Rachel and Carslaw, Ken and Desbruyères, Damien and Embury, Owen and Feltham, Daniel L. and Grosvenor, Daniel P. and Josey, Simon and King, Brian and Lewis, Alastair and McCarthy, Gerard D. and Merchant, Chris and New, Adrian L. and O'Reilly, Christopher H. and Osprey, Scott M. and Read, Katie and Scaife, Adam and Shepherd, Andrew and Sinha, Bablu and Smeed, David and Smith, Doug and Ridout, Andrew and Woollings, Tim and Yang, Mingxi (2018) Recent multivariate changes in the North Atlantic climate system, with a focus on 2005–2016. International Journal of Climatology, 38 (14). pp. 5050-5076. ISSN 0899-8418

Abstract

Major changes are occurring across the North Atlantic climate system, including in the atmosphere, ocean and cryosphere, and many observed changes are unprecedented in instrumental records. As the changes in the North Atlantic directly affect the climate and air quality of the surrounding continents, it is important to fully understand how and why the changes are taking place, not least to predict how the region will change in the future. To this end, this article characterizes the recent observed changes in the North Atlantic region, especially in the period 2005–2016, across many different aspects of the system including: atmospheric circulation; atmospheric composition; clouds and aerosols; ocean circulation and properties; and the cryosphere. Recent changes include: an increase in the speed of the North Atlantic jet stream in winter; a southward shift in the North Atlantic jet stream in summer, associated with a weakening summer North Atlantic Oscillation; increases in ozone and methane; increases in net absorbed radiation in the mid-latitude western Atlantic, linked to an increase in the abundance of high level clouds and a reduction in low level clouds; cooling of sea surface temperatures in the North Atlantic subpolar gyre, concomitant with increases in the western subtropical gyre, and a decline in the Atlantic Ocean's overturning circulation; a decline in Atlantic sector Arctic sea ice and rapid melting of the Greenland Ice Sheet. There are many interactions between these changes, but these interactions are poorly understood. This article concludes by highlighting some of the key outstanding questions.