Changes in Sea Surface Temperature (SST) can affect primary production rates, species composition and the spread of invasive species and disease as well as exacerbate sea level rise through thermal expansion. This map uses The New Zealand Earth System Model (NZESM) to compare the historical reference (2002-2019) and future (2040-2059 and 2080–2099) predictions of SST in degrees C. The future predictions show the difference between the future layer and the present layer to indicate areas with the most change in SST. Each cell of the present layer is subtracted from the corresponding cell in the future layer to show projected future change.

The recently developed New Zealand Earth System Model (NZESM) incorporates component models of ocean biogeochemistry and other aspects of biology and chemistry that provide a highly complex model of the climate system (Behrens et al. 2020, Williams et al. 2016). The NZESM model differs from the UK Earth System Model (UKESM) in that it includes a high-resolution regional ocean model for the seas around New Zealand, and it includes a representation of the variability of solar radiation in atmospheric chemistry, as solar input is an important driver of climate variability at southern high latitudes. In the NZESM the nested high-resolution ocean model domain spans from 132.7°E to 143.7°W and 60.17°S to 10.75°S with a nominal resolution of 1/5°, which translates into grid sizes of 12 to 20 km. The horizontal grid has 75 vertical levels with a thickness of 1 m at surface and increasing with depth to about 250 m. Environmental parameters were obtained from the NZESM for the midpoint of every 1x1 km cell within the New Zealand region. The interpolation of all 2-D fields for each grid point of the 1 km target grid was done through bilinear interpolation of all surrounding model grid cells, after extrapolating ocean values onto land. For the interpolation of 3-D seafloor variables, a similar approach was applied, but with consideration of vertical model grid and model bathymetry.

This NZESM can produce projections out to 200 years into the future (Williams et al. 2016). Here, we extracted predicted environmental conditions for an historical reference period (2002-2019) to represent present conditions, and two future reference periods (2040-2059, 2080–2099) to represent future conditions at different points in the current century. The predicted future conditions were based on the SSP3 (7.0 W/m2) pathway (RCP 7.0), which describes a medium-high reference scenario within the “regional rivalry” socio-economic family (O’Neill et al. 2017). Models were trained on current conditions, then fitted to these and future conditions under the future emissions pathways (SSP3-7.0). Each cell of the historical reference layer is subtracted from the corresponding cell in the future layer to create the layers shown indicating where the projected changes are greatest.

Source: National Institute of Water and Atmospheric Research Limited. (NIWA)

Behrens, E., J. Williams, O. Morgenstern, P. Sutton, G. Rickard, and M. J. M. Williams. 2020. Local Grid Refinement in New Zealand's Earth System Model: Tasman Sea Ocean Circulation Improvements and Super-Gyre Circulation Implications. Journal of Advances in Modeling Earth Systems 12:e2019MS001996. https://doi.org/10.1029/2019MS001996

Williams, J., Morgenstern, O., Varma, V., Behrens, E., Hayek, W., Oliver, H., Dean, S., Mullan, B., Frame, D. (2016) Development of the New Zealand Earth System Model: NZESM. Weather and Climate, 36: 25-44. https://doi.org/10.2307/26779386

O’Neill, B. C., E. Kriegler, K. L. Ebi, E. Kemp-Benedict, K. Riahi, D. S. Rothman, B. J. van Ruijven, D. P. van Vuuren, J. Birkmann, K. Kok, M. Levy, and W. Solecki. 2017. The roads ahead: Narratives for shared socioeconomic pathways describing world futures in the 21st century. Global Environmental Change 42:169-180. https://doi.org/10.1016/j.gloenvcha.2015.01.004

Changes in Sea Surface Temperature (SST) can affect primary production rates, species composition and the spread of invasive species and disease as well as exacerbate sea level rise through thermal expansion. This map uses The New Zealand Earth System Model (NZESM) to compare the historical reference (2002-2019) and future (2040-2059 and 2080–2099) predictions of SST in degrees C. The future predictions show the difference between the future layer and the present layer to indicate areas with the most change in SST. Each cell of the present layer is subtracted from the corresponding cell in the future layer to show projected future change.

The recently developed New Zealand Earth System Model (NZESM) incorporates component models of ocean biogeochemistry and other aspects of biology and chemistry that provide a highly complex model of the climate system (Behrens et al. 2020, Williams et al. 2016). The NZESM model differs from the UK Earth System Model (UKESM) in that it includes a high-resolution regional ocean model for the seas around New Zealand, and it includes a representation of the variability of solar radiation in atmospheric chemistry, as solar input is an important driver of climate variability at southern high latitudes. In the NZESM the nested high-resolution ocean model domain spans from 132.7°E to 143.7°W and 60.17°S to 10.75°S with a nominal resolution of 1/5°, which translates into grid sizes of 12 to 20 km. The horizontal grid has 75 vertical levels with a thickness of 1 m at surface and increasing with depth to about 250 m. Environmental parameters were obtained from the NZESM for the midpoint of every 1x1 km cell within the New Zealand region. The interpolation of all 2-D fields for each grid point of the 1 km target grid was done through bilinear interpolation of all surrounding model grid cells, after extrapolating ocean values onto land. For the interpolation of 3-D seafloor variables, a similar approach was applied, but with consideration of vertical model grid and model bathymetry.

This NZESM can produce projections out to 200 years into the future (Williams et al. 2016). Here, we extracted predicted environmental conditions for an historical reference period (2002-2019) to represent present conditions, and two future reference periods (2040-2059, 2080–2099) to represent future conditions at different points in the current century. The predicted future conditions were based on the SSP3 (7.0 W/m2) pathway (RCP 7.0), which describes a medium-high reference scenario within the “regional rivalry” socio-economic family (O’Neill et al. 2017). Models were trained on current conditions, then fitted to these and future conditions under the future emissions pathways (SSP3-7.0). Each cell of the historical reference layer is subtracted from the corresponding cell in the future layer to create the layers shown indicating where the projected changes are greatest.

Source: National Institute of Water and Atmospheric Research Limited. (NIWA)

Behrens, E., J. Williams, O. Morgenstern, P. Sutton, G. Rickard, and M. J. M. Williams. 2020. Local Grid Refinement in New Zealand's Earth System Model: Tasman Sea Ocean Circulation Improvements and Super-Gyre Circulation Implications. Journal of Advances in Modeling Earth Systems 12:e2019MS001996. https://doi.org/10.1029/2019MS001996

Williams, J., Morgenstern, O., Varma, V., Behrens, E., Hayek, W., Oliver, H., Dean, S., Mullan, B., Frame, D. (2016) Development of the New Zealand Earth System Model: NZESM. Weather and Climate, 36: 25-44. https://doi.org/10.2307/26779386

O’Neill, B. C., E. Kriegler, K. L. Ebi, E. Kemp-Benedict, K. Riahi, D. S. Rothman, B. J. van Ruijven, D. P. van Vuuren, J. Birkmann, K. Kok, M. Levy, and W. Solecki. 2017. The roads ahead: Narratives for shared socioeconomic pathways describing world futures in the 21st century. Global Environmental Change 42:169-180. https://doi.org/10.1016/j.gloenvcha.2015.01.004