NSF Award
2423761
Non-technical abstract<br/><br/>Earth’s climatic changes have been recorded in the ice core collected from the Antarctic ice sheet. While these records provide a high resolution view of how polar temperatures changed through time, it is not always clear what Earth process influence Antarctic climate. One likely contributor to Antarctic temperature changes is the cyclic changes in Earth’s orientation as it orbits the sun. These so-called Milankovitch cycles control the amount and pattern of sunlight reaching the polar regions, that in turn result in periods of climatic warming or cooling. While the orbital variations and control on incoming solar energy remain well understood, how they influence Antarctic climate remains unresolved. It is the goal of this project to determine how variations in Earth’s orbit may be locally influencing Antarctic temperatures. The researchers on this project are pursing this goal by identifying periods of past ice melting on the surface of Antarctica using minerals that precipitate from the meltwaters that resulted from past warm periods. The timing of this past melting will be determined by radioisotopic dating of the minerals using the natural radioactive decay of uranium to thorium. By dating numerous samples, collected in past scientific expeditions throughout the Antarctic continent, these researchers aim to reconstruct the frequency and spatial pattern of past warming and in doing so, determine what aspect of Earth’s orbital variations influences Antarctic ice loss.<br/><br/>Technical abstract<br/><br/>Antarctic ice cores provide high resolution records of Pleistocene Southern Hemisphere temperatures that show an overall coherence with Northern Hemisphere temperature variations. One explanation for this bi-hemispheric temperature covariance relies on changes in atmospheric CO2 that result from varying northern hemisphere insolation. An alternative posits that the apparent coherence of polar temperatures is due to the misleading covariance between northern hemisphere summer insolation and, the southern hemisphere summer duration. At present there is an insufficient understanding of the role that local insolation plays in Antarctic climate. The goal of this research project is to identify the temporal spatial patterns of solar forcing in Antarctica. To reach this goal, the project team will: 1) develop a way to identify periods of past surface melt production in Antarctica using U-Th dating of pedogenic carbonates; and 2) utilize the evidence of past surface melting to calibrate energy balance models and interrogate past Antarctic surface temperatures and; 3) compare the timing of Antarctic warm periods to potential solar forcing mechanisms such as peak summer insolation or summer duration. A means of identifying the spatial and temporal pattern at which local insolation influences Antarctic temperature would provide a transformative solution to the contradiction in current climate records.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
