Northeast Greenland glaciers


In northeastern Greenland there is a huge ice flow that transports ice far from inside the ice sheet to the coast. Over 10% of the entire mainland ice of Greenland drains here mainly via two large glaciers: Zachariæ Isstrøm and Nioghalvfjerdsbræ. The latter is also known as the 79° N Glacier and protrudes far out over the ocean: its floating glacier tongue is 80 km long and the ocean water circulates under it. The Zachariæ Isstrøm glacier tongue, on the other hand, has fallen victim to climate change in recent years - it is retreating strongly and huge icebergs break off on its calving front ...

Figure 1: Grounding lines and calving fronts of the Zachariæ Isstrøm (ZI) and the 79°N Glacier according to Mouginot et al. (2015). Image A: Scheme with the flight courses of Operation Ice Bridge and other NASA missions (gray lines) as well as touchdown lines (black) and calving front positions (green lines). Image C: Differential interferogram showing the retreat of the touchdown line of the Zachariæ Isstrøm from 1996 to 2015.

Regional differences

So far, ice loss has mainly been observed on Greenland's southeastern and western outlet glaciers and the peripheral glaciers [22,23,32,33,34], in which fjords warm Atlantic water from the subpolar North Atlantic circulates. The retreat of the glaciers there began at the same time as the accumulation and warming of Atlantic water [35]. But in recent years, the warming of the North Atlantic has also penetrated into the European Arctic Ocean and the Arctic [36,37]. This raises the question of the extent to which this warming has also reached the marine terminating glaciers on the northeast coast of Greenland, which were considered stable until a few years ago. There is the only large ice stream in Greenland, the "Northeast Greenland Icestream" (NEGIS), which drains over three glaciers: Zachariæ Isstrøm, Nioghalvfjerdsbræ (also called 79°N Glacier) and Storstrømmen Glacier.

The 79°N Glacier and Zachariæ Isstrøm

The largest glacier in Northeast Greenland, currently still at the beginning of the retreat, is the 79°N Glacier (Figure 1a). For some years now, this glacier has also been losing mass due to acceleration [38]. On the other hand, its immediate neighbor, the Zachariæ Isstrøm, has lost its entire ice tongue in recent years and as a result has accelerated and experienced a retreat of the grounding line and is now a so-called tidewater glacier (Figure 1). Both glaciers together drain over 10% of the entire Greenland ice sheet, so an increase in mass loss causes a significant change in Greenland's total contribution to sea level rise. The outflow of ice for both glaciers has increased due to the warming of the ocean and atmosphere [38]  In our research project GROCE, we are examining this interplay between atmosphere - ocean - glacier - ice sheet in detail - in order to gain a better understanding of the governing processes.