60 million years of glaciation in the Transantarctic Mountains

The Antarctic continent reached its current polar location ~83 Ma and became shrouded by ice sheets ~34 Ma, coincident with dramatic global cooling at the Eocene-Oligocene boundary. However, it is not known whether the first Antarctic glaciers formed immediately prior to this or were present significantly earlier. Here we show that mountain glaciers were likely present in the Transantarctic Mountains during the Late Palaeocene (~60–56 Ma) and middle Eocene (~48–40 Ma). Temperate (warm-based) glaciers were prevalent during the Late Eocene (~40–34 Ma) and, in reduced numbers, during the Oligocene (~34–23 Ma), before larger, likely cold-based, ice masses (including ice sheets) dominated. Some temperate mountain glaciers were present during the Miocene Climatic Optimum (~15 Ma), before a widespread switch to cold-based glaciation. Our findings highlight the longevity of glaciation in Antarctica and suggest that glaciers were present even during the Early-Cenozoic greenhouse world

Mass Loss of Glaciers and Ice Caps Across Greenland Since the Little Ice Age

Abstract Glaciers and ice caps (GICs) are important contributors of meltwater runoff and to global sea level rise. However, knowledge of GIC mass changes is largely restricted to the last few decades. Here we show the extent of 5327 Greenland GICs during Little Ice Age (LIA) termination (1900) and reveal that they have fragmented into 5467 glaciers in 2001, losing at least 587 km3 from their ablation areas, equating to 499 Gt at a rate of 4.34 Gt yr−1. We estimate that the long-term mean mass balance in glacier ablation areas has been at least −0.18 to −0.22 m w.e. yr−1 and note the rate between 2000 and 2019 has been three times that. Glaciers with ice-marginal lakes formed since the LIA termination have had the fastest changing mass balance. Considerable spatial variability in glacier changes suggest compounding regional and local factors present challenges for understanding glacier evolution. Key Points Total volume loss of at least 587 km3 since the Little Ice Age (LIA) termination, equating to 499 Gt and to 1.38 mm sea level equivalent Glacier mass balance from 2000 to 2019 is three times more negative than since the LIA but five times more negative in the North region Lake-terminating glaciers have experienced the greatest change in rate of mass loss Plain Language Summary Glaciers and ice caps of Greenland peripheral to the ice sheet are important contributors of meltwater to the oceans and to global sea-level rise. In this study we map the extent of 5467 glaciers during the Little Ice Age (LIA) termination c. 1900 and calculate that they have lost at least 587 km3. The rate of mass change of these glaciers between 2000 and 2019 was three times more negative than the long-term average (of 4.34 Gt yr−1) since the LIA. Lake-terminating glaciers now lose mass the fastest compared with land- or marine-terminating glaciers. Considerable spatial variability in glacier responses suggests local factors are important and makes glacier evolution complex