Historical trends in Southern Ocean storminess: Long‐term variability of extreme wave heights at Cape Sorell, Tasmania

[1] Atmospheric re-analyses indicate increased Southern Ocean (SO) storminess over the past few decades. A southern Australia waverider record provides a 23-year record of storm waves generated in the SO. Statistical models to estimate long-term trends in frequency and intensity of severe storm waves, based on time-dependent versions of the Peak over Threshold model, are applied to investigate SO storminess trends. Significant increase in frequency of storm wave events observed in the corrected ERA-40 re-analysis significant wave height (H S ) record is supported by increasing frequency of synoptic storms which drive large wave events at the site in both ERA-40 and NCEP-NCAR re-analyses. However buoy data show a small decrease in storm wave event frequency, consistent with previous studies investigating trends in SO mean H s from altimeter records. Re-analysis winds, with apparent increasing trend, may have influenced prior SO research conclusions, particularly related to weakening of the SO CO 2 sink.

[1]  Casper Labuschagne,et al.  Saturation of the Southern Ocean CO2 Sink Due to Recent Climate Change , 2007, Science.

[2]  S. Rintoul,et al.  The response of the Antarctic Circumpolar Current to recent climate change , 2008 .

[3]  J. Hunter,et al.  Variability and trends in the directional wave climate of the Southern Hemisphere , 2010 .

[4]  A. Sterl,et al.  The ERA‐40 re‐analysis , 2005 .

[5]  Inigo J. Losada,et al.  Estimation of the long‐term variability of extreme significant wave height using a time‐dependent Peak Over Threshold (POT) model , 2006 .

[6]  G. Marshall Trends in the Southern Annular Mode from Observations and Reanalyses , 2003 .

[7]  R. Huang,et al.  Decadal Changes of Wind Stress over the Southern Ocean Associated with Antarctic Ozone Depletion , 2007 .

[8]  Greg J. Holland,et al.  Atlas of the Oceans: Wind and Wave Climate , 1996 .

[9]  Ian Simmonds,et al.  A classification of wave generation characteristics during large wave events on the Southern Australian margin , 2008 .

[10]  K. Keay,et al.  Variability of Southern Hemisphere extratropical cyclone behavior, 1958-97 , 2000 .

[11]  S. Caires,et al.  Climatology, variability and extrema of ocean waves: the Web‐based KNMI/ERA‐40 wave atlas , 2005 .

[12]  A. Lenton,et al.  Impact of Historical Climate Change on the Southern Ocean Carbon Cycle , 2008 .

[13]  R. Reynolds,et al.  The NCEP/NCAR 40-Year Reanalysis Project , 1996, Renewable Energy.

[14]  David K. Woolf,et al.  Assessment of the reliability of wave observations from voluntary observing ships: Insights from the validation of a global wind wave climatology based on voluntary observing ship data , 2003 .

[15]  H. Akaike,et al.  Information Theory and an Extension of the Maximum Likelihood Principle , 1973 .

[16]  Inigo J. Losada,et al.  Variability of extreme wave heights in the northeast Pacific Ocean based on buoy measurements , 2008 .

[17]  A. Sterl,et al.  On the (In)Homogeneity of Reanalysis Products , 2004 .