Illustration of the effects of the North Atlantic Oscillation and Southern Annular Modes of climate variability

The illustration shows two modes of natural variability in the climate controlled by variations in the large scale surface pressure fields – the North Atlantic Oscillation and the Southern Annular Mode. The positive phase of the North Atlantic Oscillation is characterised by a deepening of the low pressure over Iceland and increased pressure around the Azores high pressure area. It brings warm and wet conditions over northern Europe in winter and cool dry conditions further south. The negative phase is characterised by a weakening of the Icelandic low and Azores high with the opposite impacts. The positive phase of the Southern Annual Mode is characterised by anomalously low pressure over Antarctica and higher pressure at lower latitudes. In the negative phase this pattern is reversed. Time series of the two modes are shown from 1825 to 2023. Further information about these modes can be found in Schurer et al. ( 2023a ; 2023b ) Schurer, A., Hegerl, G.C., Goosse, H., Bollasina, M.A., England, M.H., Smith, D., Tett, S.F. (2023a) Role of multi-decadal variability of the winter North Atlantic oscillation on northern hemisphere climate, Environmental Research Letters, 18(4), doi: 10.1088/1748-9326/acc477 Schurer, A.P., Hegerl, G.C., Goosse, H., Bollasina, M.A., England, M.H., Mineter, M.J., Smith, D.M., Tett, S.F.B. (2023b) Quantifying the contribution of forcing and three prominent modes of variability to historical climate, Climate of the Past, 19, 943–957, doi: 10.5194/cp-19-943-2023 Data: NAO: https://crudata.uea.ac.uk/cru/data/nao/nao_3dp.dat SAM: https://www.ncei.noaa.gov/pub/data/paleo/contributions_by_author/abram2014/abram2014sam-noaa.txt http://www.nerc-bas.ac.uk/public/icd/gjma/newsam.1957.2007.seas.txt Code associated with this figures is available at https://github.com/jjk-code-otter/glosat-graphics