show a dry period around 11.6 ka, steadily becoming wetter through the early Holocene. The mid-late Holocene was punctuated by millennial-scale variability, associated with the El Niño-Southern Oscillation; this is evident in the marine, coral, speleothem and pollen records of the region.
Abstract. The Southern Annular Mode (SAM) is the leading mode of climate
variability in the extratropical Southern Hemisphere, with major regional
climate impacts. Observations, reconstructions, and historical climate
simulations all show positive trends in the SAM since the 1960s; however,
earlier trends in palaeoclimate SAM reconstructions cannot be reconciled
with last millennium simulations. There are also large differences in the
magnitude of solar irradiance change between various solar reconstructions,
although most last millennium climate simulations have relied on a
low-amplitude solar-forcing scenario. Here we investigate the sensitivity of
the SAM to solar irradiance variations using simulations with a range of
constant solar-forcing values and last millennium transient simulations
with varying amplitude solar-forcing scenarios. We find the mean SAM state
can be significantly altered by solar irradiance changes and that transient
last millennium simulations using a high-amplitude solar scenario have an
improved and significant agreement with proxy-based SAM reconstructions. Our
findings suggest that the effects of solar forcing on high-latitude climate
may not be adequately incorporated in most last millennium simulations due
to solar irradiance changes that are too small and/or the absence of
interactive atmospheric chemistry in the global climate models used for
these palaeoclimate simulations.
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