Category: Spring 2023

Hydrographic properties of the upper ocean on the South Orkney Plateau, Antarctica, from austral summer 2011-2020 are processed using data collected alongside krill trawlings. This shows good applicability of this method and contributes to improved hydrographic monitoring. The results show clear salinity driven stratification. The fresh and warm surface water displays a positive northward temperature gradient. Below the upper pycnocline the colder and more saline Winter Water was found. In some years indications of the Upper Circumpolar Deep Water was also found, which indicates the southern boundary of the Antarctic Circumpolar Current. On an inter-annual scale, the surface waters exhibit large variability. Years with more sea ice free days prior to sampling have warmer and more saline surface properties and vice versa. No direct link between the hydrographic properties and the Antarctic krill (Euphasia Superba) abundance and distribution was found. This is likely due to correlations with additional factors and is subject to further work.

The ocean around Antarctica – the Southern Ocean, is a major player for biological production and global ocean circulation. The currents around Antarctica connect and mix the water masses of the Pacific, the Atlantic and the Indian Ocean. This is the Antarctic Circumpolar Current (ACC), a wind driven current and the strongest current in the world. The strong flow also isolate Antarctica from warm waters to the north, keeping it cool. This is an important feature for sea-ice production. The same winds that drive the ACC also drive Ekman-upwelling both a lower and an upper cell. This is critical for the overturning of deep and bottom water. Since the deeper upwelling water is nutrient rich, the Southern Ocean mixed layer is a favourable place for biology. One famous example is the Southern Ocean trap. This is a feature that traps dissolved silicon in the region, making it the habitat for many silicifiers, for example diatoms and radiolaria. Going in the opposite direction as the ACC is the slope current. This current is generated by dense sinking water masses that are deflected by the Coriolis force.

The Greenland Ice Sheet (GrIS) has rapidly been loosing mass since the 1990s. It is attributed to increased surface melting and accelerated ice flow, driven in equal parts by the atmosphere and the ocean. However, the ocean forcing has received growing attention in past studies as more evidence of warm water entering deep glacial fjords around Greenland became available. Many such fjords host marine-terminating glaciers, which undergo melting if warm waters encounter the ice front at depth. The primary source of oceanic heat along the coastal margins of Greenland is the Atlantic Water (AW). Typically, in the range of 0 to 4°C, this water mass can bring enough heat to drive a substantial submarine melt. However, given the vastness of the Greenlandic continent, its oceanographic setting varies geographically, and the AW has different properties and vertical distribution along the coasts of Greenland. Combined with varying topography, sea ice, and atmospheric conditions, the ocean forcing to GrIS is thus spatially non-uniform. This poster will outline the regional differences in AW properties along the Greenland continental shelf. We will discuss examples of well-studied glacial fjords along West and East Greenland, outlining the processes associated with the presence of AW.

Sea ice albedo feedback (SIAF) is a strong positive feedback process in Earth’s climate system. Melting of highly reflective sea ice results in higher absorption of solar energy, leading to warmer temperatures that again amplify sea ice melt and lead to ocean warming. In the Arctic, SIAF is an intricate process with a prominent seasonal lag in the melting of sea ice and heat absorption associated with the high amount of solar radiation during spring and summer in the northern hemisphere. Studies have shown that a 50% increase in the accumulated heat absorption observed at the end of August is due to SIAF. For annual values estimates reach up to a 4% increase in absorbed solar radiation of the Pacific region of the Arctic, as a result of sea ice reduction the last two decades. Some extreme ice-free scenarios predict an annual global mean radiative heat increase comparable to a trillion tons of CO2 emissions that would accelerate global warming by 25 years. Despite all this evidence, there is a lot to uncover regarding the complex interplay of SIAF with several other physical factors. Such factors are cloud cover variability, meltpond distribution, atmospheric and oceanic circulation patterns, longwave radiative forcing due to anthropogenic CO2 emissions. All these can potentially contribute to drastic sea ice reductions and consequently accelerate warming of the global climate.

Sea ice plays a crucial role in polar marine ecosystems, serving as a nutrient reservoir and supporting microbial life that contributes to nutrient cycling. This poster explores the relationship between sea ice and nutrient dynamics. Processes such as ice melt, brine drainage, and wind-driven mixing affect nutrient surface concentrations and impact ocean stratification and nutrient distribution in the water column. The essential role of sea ice microbial communities, particularly algae, in nutrient cycling and marine food webs is highlighted. Furthermore, the poster examines the contrasting effects of sea ice on nutrient availability, revealing that nutrient-rich meltwater enhances primary production at the ice edge, while the presence of sea ice can simultaneously limit nutrient exchange between the atmosphere and the ocean. By deepening our understanding of these processes, we can better grasp the implications of climate change on the polar oceans and develop effective strategies to protect and conserve these ecosystems in a rapidly changing world.