Freshwater variability in the AO and SPNA: a Comparison from the 1990s to Present References

A significant increase in liquid freshwater content has been observed in the Arctic Ocean over the last 20 years, whereas the Arctic sea ice volume shrank significantly. In contrast, the North Atlantic became more saline in recent years. Both regions are of great importance for the global ocean circulation and climate, and salinity changes may have a profound impact on the global climate. We found that for the period between 1992 and 2013, the liquid freshwater content of the subpolar North Atlantic, calculated from objectively mapped in-situ salinity measurements, and the total freshwater content of the Arctic Ocean, i.e. the liquid freshwater content and freshwater stored in sea ice, are significantly negative correlated (r=-0.77). Moreover, the amount of the anomalies are of the same size. Furthermore, the time series hint at multi-decadal oscillations. The highest negative correlation with the total freshwater content of the Arctic Ocean can be found in the Irminger and Labrador Seas, while we observed a positive correlation east of the Mid-Atlantic Ridge at the path of the North Atlantic Current, which is the source of Atlantic Water entering the Arctic Ocean through the Nordic Seas. We suggest a redistribution of freshwater as a response to frequent changes in atmospheric pressure patterns. Under certain conditions the freshwater is re-routed and kept in the Arctic Ocean, while it is released under other conditions. We conclude that decadal scale changes of the freshwater content in the North Atlantic, particularly those in the deep water formation sites like the Labrador Sea, are originating in the Arctic Ocean

Link between multidecadal freshwater anomalies in the Arctic Ocean and subpolar North Atlantic

A significant increase in liquid freshwater content has been observed in the Arctic Ocean over the last 20 years, whereas the Arctic sea ice volume shrank significantly. In contrast, the North Atlantic became more saline in recent years. Both regions are of great importance for the global ocean circulation and climate, and salinity changes may have a profound impact on the global climate. We found that for the period between 1992 and 2013, the liquid freshwater content of the subpolar North Atlantic, calculated from objectively mapped in-situ salinity measurements, and the total freshwater content of the Arctic Ocean, i.e. the liquid freshwater content and freshwater stored in sea ice, are significantly negative correlated (r=-0.77). Moreover, the amount of the anomalies are of the same size. Furthermore, the time series hint at multi-decadal oscillations. The highest negative correlation with the total freshwater content of the Arctic Ocean can be found in the Irminger and Labrador Seas, while we observed a positive correlation east of the Mid-Atlantic Ridge at the path of the North Atlantic Current, which is the source of Atlantic Water entering the Arctic Ocean through the Nordic Seas. We suggest a redistribution of freshwater as a response to frequent changes in atmospheric pressure patterns. Under certain conditions the freshwater is re-routed and kept in the Arctic Ocean, while it is released under other conditions. We conclude that decadal scale changes of the freshwater content in the North Atlantic, particularly those in the deep water formation sites like the Labrador Sea, are originating in the Arctic Ocean

Year-round under-ice research on MOSAiC using a remotely operated vehicle

To provide easy and reliable access to the underside of the sea-ice during the MOSAiC expedition, the Alfred-Wegener-Institute will operate its new remotely operated vehicle during the full duration of the drift directly from an access hole on the ice. The vehicle has proven its capabilities during several Arctic field campaigns and provides a stable sensor platform, as well as inspection and intervention capabilities. It has a maximum range of 300m from the designated access hole(s) and a depth rating of 100m. The ROV operations under sea ice will allow repeat measurements during the entire drift with little impact to the sea ice, the upper ocean, the ecosystem and other objects of interest. In the current setup, the vehicle comprises various video cameras, a still camera, single and multibeam bathymetric sonar, scanning sonar, a CTD, triplet fluorometer as well as sensors for hyperspectral irradiance, radiance, extinction, dissolved oxygen, pH and nitrate. The vehicle position is recorded by acoustic positioning tied into the floe fixed reference frame of all observations on the central observatory floe. Beyond this, the vehicle also provides several additional power outlets and data ports that allow connecting additional systems to the vehicle. Currently, the integration of a current profiler (ADCP), a zooplankton camera, different nets for zooplankton sampling, as well as a water sampling system are under development. All data are recorded, timestamped on site, and will be uploaded to an open data portal, which will be easily accessible for the scientific community. The main task of the vehicle will be repeated mapping of the spatial variability of the various parameters on a weekly basis. In addition, we plan to use it for deployment and retrieval of under-ice sensor packages and perform inspection and manipulation tasks. The ROV operations can easily be conducted by a small on-board sea-ice team due to the reliable and redundant system architecture. Altogether, measurements give a comprehensive picture of the spatio-temporal evolution of the sea-ice and its associated ecosystem. They link upper ocean dynamics with the thermodynamic and dynamic development of the ice cover. In combination with surface measurements, like aerial photography and terrestrial laser scanning, a full 3D characterization of the local ice cover will enable areal upscaling of the obtained results also using remote sensing data. Ideally these high resolution measurements at the MOSAiC central observatory will be extended with regular missions of an autonomous underwater vehicle (AUV), which can travel longer distances in spite of a small logistical footprint, to tie the local observations into the context of the larger spatial scale of the MOSAiC distributed measurement network

Arctic sea ice thickness variability and change

Arctic sea ice thickness variability and change and their dependence on the atmospheric and oceanic forcing are at the core of research in Subtopic 2.1, Theme: Ongoing and Future Arctic and Antarctic Climate Change. Our research is particularly focused on a better process understanding and representation in models, and observations during MOSAiC play a strong role. The poster gives examples of such process studies focused on Arctic sea ice thickness variability and change. We outline observations of the long-term and regional variability and change of sea ice thickness using satellite remote sensing, airborne surveying, and ice mass balance buoys. Thermodynamic growth and its interaction with the atmosphere over leads and level ice serves as an example for our joint research interests. The poster also gives examples of causes of sea ice thinning, like increased ocean heat flux to the ice due to Atlantification, and consequences, e.g., for reduced sea ice volume transport through Fram Strait

An autonomous, multi-disciplinary sea ice - atmosphere - ocean observatory in the central Arctic

Although the polar oceans have been studied extensively during recent decades, year-round direct observations of sea ice, atmosphere and ocean are still relatively sparse. Hence, significant knowledge gaps exist in their complex interactions, and how they impact the evolution of the polar marine ecosystems. An important tool to fill these gaps has been developed and enhanced in recent years: autonomous, ice-based observation platforms. These buoys are capable of obtaining data on basin scales and year-round, including the largely undersampled winter periods. A key advantage over other observatory systems is that they send data in near-real time via satellite, contributing for example to numerical weather predictions through the Global Telecommunication Network (GTS). Here we present a concept for the implementation of a long-term strategy to monitor essential physical and biogeochemical parameters in the central Arctic Ocean year round and synchronously. We propose a combination of several new and innovative types of ice-based buoys, such as weather stations, ice mass balance buoys, ice-tethered bio-optical buoys and upper ocean profilers, with a scientific payload optimized to enable interdisciplinary research. Over the next 4 years, including the observational periods of the Year of Polar Prediction (YOPP, 2017-2019) and the Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC, 2020), a network of these platforms will be (re-)deployed in the central Arctic Ocean each year, benefitting from international logistical efforts. The ultimate aim is to achieve a quasi-synoptic, basin-wide coverage of key parameters, such as air temperature, barometric pressure, wind speed and –direction, ice and snow thickness, incoming, reflected and transmitted irradiance, seawater temperature and salinity, chl-a and CDOM fluorescence, turbidity, oxygen and nitrate. Initial results from similar deployments since 2015 suggest that this approach has great potential to advance our understanding of many physical and biogeochemical processes and interactions in the polar oceans

A distributed atmosphere - sea ice - ocean observatory in the central Arctic

To understand the current evolution of the Arctic Ocean towards a less extensive, thinner and younger sea ice cover is one of the biggest challenges in climate research. Especially the lack of simultaneous in-situ observations of sea ice, ocean and atmospheric properties leads to significant knowledge gaps in their complex interactions, and how the associated processes impact the polar marine ecosystem. Here we present a concept for the implementation of a long-term strategy to monitor the most essential climate- and ecosystem parameters in the central Arctic Ocean, year round and synchronously. The basis of this strategy is the development and enhancement of a number of innovative autonomous observational platforms, such as rugged weather stations, ice mass balance buoys, ice-tethered bio-optical buoys and upper ocean profilers. The deployment of those complementing platforms in a distributed network enables the simultaneous collection of physical and biogeochemical in-situ data on basin scales and year round, including the largely undersampled winter periods. A key advantage over other observatory systems is that the data is sent via satellite in near-real time, contributing to numerical weather predictions through the Global Telecommunication Network (GTS) and to the International Arctic Buoy Programme (IABP). The first instruments were installed on ice floes in the Eurasian Basin in spring 2015 and 2016, yielding exceptional records of essential climate- and ecosystem-relevant parameters in one of the most inaccessible regions of this planet. Over the next 4 years, and including the observational periods of the Year of Polar Prediction (YOPP, 2017-2019) and the Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC, 2020), the distributed observatory will be maintained by deployment of additional instruments in the central Arctic each year, benefitting from international logistical efforts

A distributed atmosphere - sea ice - ocean observatory in the central Arctic Ocean: concept and first results

To understand the current evolution of the Arctic Ocean towards a less extensive, thinner and younger sea ice cover is one of the biggest challenges in climate research. Especially the lack of simultaneous in-situ observations of sea ice, ocean and atmospheric properties leads to significant knowledge gaps in their complex interactions, and how the associated processes impact the polar marine ecosystem. Here we present a concept for the implementation of a long-term strategy to monitor the most essential climate- and ecosystem parameters in the central Arctic Ocean, year round and synchronously. The basis of this strategy is the development and enhancement of a number of innovative autonomous observational platforms, such as rugged weather stations, ice mass balance buoys, ice-tethered bio-optical buoys and upper ocean profilers. The deployment of those complementing platforms in a distributed network enables the simultaneous collection of physical and biogeochemical in-situ data on basin scales and year round, including the largely undersampled winter periods. A key advantage over other observatory systems is that the data is sent via satellite in near-real time, contributing to numerical weather predictions through the Global Telecommunication Network (GTS) and to the International Arctic Buoy Programme (IABP). The first instruments were installed on ice floes in the Eurasian Basin in spring 2015 and 2016, yielding exceptional records of essential climate- and ecosystem-relevant parameters in one of the most inaccessible regions of this planet. Over the next 4 years, and including the observational periods of the Year of Polar Prediction (YOPP, 2017-2019) and the Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC, 2020), the distributed observatory will be continued and extended by deployments of additional instruments in the central Arctic each year, benefitting from international logistical efforts. The continuous data generated by this new autonomous drifting system is expected to provide new insights into the complex Arctic climate- and ecosystem on multiple scales. It is especially valuable in the context of the MOSAiC experiment, extending its coverage both in space and time