Emperor penguins on Antarctica forced into refugia during last glacial maximum

Research of biologists published in Global Change Biology indicates that emperor penguins on Antarctica were forced into refugia by extreme cold during the last glacial maximum (~ 19.5 – 16 thousand years ago). By comparing the DNA of fossil emperor penguins with the DNA of living individuals and colonies, the scientists were able to reconstruct the population dynamics of emperor penguins on Antarctica through time. Their results show three mitochondrial clades within emperor penguins at the time of the last glacial maximum, which suggests that these birds were isolated in three small, separate populations and may have survived in refugia such as the Ross Sea. The population sizes of emperor penguins are related to the balance between sea ice available for breeding and open water available for foraging. Sea ice extent around Antarctica was much greater during the last glacial maximum than at present and therefore, reduced food availability resulted in severe losses among populations of emperor penguins.

Journal reference: Younger, J. L., Clucas, G. V., Kooyman, G., Wienecke, B., Rogers, A. D., Trathan, P. N., … & Miller, K. J. (2015). Too much of a good thing: sea ice extent may have forced emperor penguins into refugia during the last glacial maximum. Global change biology21(6), 2215-2226.

Image: Emperor penguin colony foraging along the Weddell Sea, Antarctica. Source: Christopher Michel, Wikimedia Commons.

Sahara desert may be older than previously thought

New findings of climatologists published in Nature reveal that the formation of the Sahara desert may have started up to 7 million years ago, more than twice as long ago as previously thought. Following the discovery of aeolian dune deposits that challenged the widely accepted age of approximately 2 – 3 million years for the Sahara desert, the scientists have used climate models to simulate the mechanisms behind the onset of aridification in northern Africa. Their results show that the origination of the Sahara desert may be related to shrinking of the Tethys Sea and the uplift of the Arabian Peninsula, associated with the northward movement of the African tectonic plate towards the Eurasian tectonic plate during the late Miocene. This reorganization of landmasses is thought to have significantly weakened the African summer monsoon, resulting in a reduced flow of moisture from the Atlantic Ocean and increasingly arid conditions in northern Africa. Until now, it was long believed that the desertification of northern Africa was related to the onset of glaciation on the Northern Hemisphere during the Pliocene and Pleistocene.

Journal reference: Zhang, Z., Ramstein, G., Schuster, M., Li, C., Contoux, C., & Yan, Q. (2014). Aridification of the Sahara desert caused by Tethys Sea shrinkage during the Late Miocene. Nature, 513(7518), 401-404.

Image: Sand dunes of the Sahara desert at sunset in Fezzan, Libya. Source: Luca Galuzzi, Wikimedia Commons.

Antarctic sea level rising faster than global sea level

Climatologists at the University of Southampton have discovered that over the past 19 years, sea level around the coast of Antarctica has risen 2 cm more than the global average rise of 6 cm. They have detected this rapid sea level rise by studying detailed satellite images of an area spanning over a million square kilometers and have attributed it to the melting of fresh water from the Antarctic glaciers and ice shelves, which is further supported by a decrease in the salinity of the surrounding ocean waters. In order to explain these observations, the scientists estimate that a total discharge of approximately 430 Gt of fresh water to the surrounding ocean is required. Furthermore, global ocean circulation model simulations of the effects of melting ice on the Antarctic Ocean closely match their findings.

Journal reference: Rye, C. D., Garabato, A. C. N., Holland, P. R., Meredith, M. P., Nurser, A. G., Hughes, C. W., … & Webb, D. J. (2014). Rapid sea-level rise along the Antarctic margins in response to increased glacial discharge. Nature Geoscience7(10), 732-735.

Image: Melting icebergs along the Antarctic Peninsula, Antarctica. Source: Christopher Michel, Wikimedia Commons.