Abstract
Abstract. High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections. Here, we present data from a new, annually dated ice core record from the eastern Ross Sea, named the Roosevelt Island Climate Evolution (RICE) ice core. Comparison of this record with climate reanalysis data for the 1979–2012 interval shows that RICE reliably captures temperature and snow precipitation variability in the region. Trends over the past 2700 years in RICE are shown to be distinct from those in West Antarctica and the western Ross Sea captured by other ice cores. For most of this interval, the eastern Ross Sea was warming (or showing isotopic enrichment for other reasons), with increased snow accumulation and perhaps decreased sea ice concentration. However, West Antarctica cooled and the western Ross Sea showed no significant isotope temperature trend. This pattern here is referred to as the Ross Sea Dipole. Notably, during the Little Ice Age, West Antarctica and the western Ross Sea experienced colder than average temperatures, while the eastern Ross Sea underwent a period of warming or increased isotopic enrichment. From the 17th century onwards, this dipole relationship changed. All three regions show current warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea but increasing in the western Ross Sea. We interpret this pattern as reflecting an increase in sea ice in the eastern Ross Sea with perhaps the establishment of a modern Roosevelt Island polynya as a local moisture source for RICE.
Highlights
The recent change to a strongly negative Southern Annular Mode (SAM) (Marshall Index −3.12) in November 2016 coincided with a significant reduction in Antarctic sea ice extent (SIE), including the Ross Sea, during the 2016/17 summer (Turner et al, 2017)
Longer observations are necessary to assess whether this recent trend continues and forces the reduced SIE, but it fuels questions on the potential acceleration of future environmental change in the Antarctic/Southern Ocean region
The Amundsen Sea Low (ASL) has been shown to deepen during coinciding positive SAM and La Niña events and to weaken during negative SAM and El Niño events
Summary
With carbon dioxide (CO2) and global temperatures predicted to continue to rise, model simulations of the Antarctic/Southern Ocean region show an increase in surface warming for the coming decades resulting in reduced sea ice extent, weakened Antarctic Bottom Water formation, intensified zonal winds that reduce CO2 uptake by the Southern Ocean, a slowing of the southern limb of the meridional overturning circulation (MOC) and associated changes in global heat transport, and a rapid ice sheet grounding line retreat that contributes to global sea level rise (Kusahara and Hasumi, 2013; Spence et al, 2012; Marshall and Speer, 2012; Sen Gupta et al, 2009; Toggweiler and Russell, 2008; Russell et al, 2006; Downes et al, 2010; Anderson et al, 2009; DeConto and Pollard, 2016; Joughin and Alley, 2011; Golledge et al, 2015; DeVries et al, 2017). Observations confirm an ozone-depletion-induced strengthening and poleward contraction of zonal winds (Thompson and Solomon, 2002b; Arblaster et al, 2011), increased upwelling of warm, modified Circumpolar Deep Water (Jacobs et al, 2011), a warmer Southern Ocean (Böning et al, 2008; Gille, 2002; Abraham et al, 2013), meltwater-driven freshening of the Ross Sea (Jacobs et al, 2002), ice shelf and mass loss, grounding line retreat (Rignot et al, 2014; Pollard et al, 2015; Paolo et al, 2015; Joughin et al, 2014), reduced formation of Antarctic Bottom Water (Rintoul, 2007) and Antarctic Intermediate Water (Wong et al, 1999), changes in sea ice (regional decreases and increases in the Amundsen and Ross seas, respectively) (Holland and Kwok, 2012; Sinclair et al, 2014; Stammerjohn et al, 2012), and dynamic changes in Southern Ocean CO2 uptake driven by atmospheric circulation (Landschützer et al, 2015) These observational time series are short (Böning et al, 2008; Gille, 2002; Toggweiler and Russell, 2008) and inter-model variability indicates that physical processes and their consequences are not well captured or understood (Braconnot et al, 2012; Sen Gupta et al, 2009). The Roosevelt Island Climate Evolution (RICE) ice core is compared with existing records in the region to investigate the characteristics and drivers of spatial and temporal climate variability in the Ross Sea region
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