Mateusz Moskalik

Underwater acoustic signatures of glacier calving

Climate-driven ice-water interactions in the contact zone between marine-terminating glaciers and the ocean surface show a dynamic and complex nature. Tidewater glaciers lose volume through the poorly understood process of calving. A detailed description of the mechanisms controlling the course of calving is essential for the reliable estimation and prediction of mass loss from glaciers. Here we present the potential of hydroacoustic methods to investigate different modes of ice detachments. High-frequency underwater ambient noise recordings are combined with synchronized, high-resolution, time-lapse photography of the Hans Glacier cliff in Hornsund Fjord, Spitsbergen, to identify three types of calving events: typical subaerial, sliding subaerial, and submarine. A quantitative analysis of the data reveals a robust correlation between ice impact energy and acoustic emission at frequencies below 200 Hz for subaerial calving. We suggest that relatively inexpensive acoustic methods can be successfully used to provide quantitative descriptions of the various calving types.

Variability in transport of terrigenous material on the shelves and the deep Arctic Ocean during the Holocene

Arctic coastal zones serve as a sensitive filter for terrigenous matter input onto the shelves via river discharge and coastal erosion. This material is further distributed across the Arctic by ocean currents and sea ice. The coastal regions are particularly vulnerable to changes related to recent climate change. We compiled a pan-Arctic review that looks into the changing Holocene sources, transport processes and sinks of terrigenous sediment in the Arctic Ocean. Existing palaeoceanographic studies demonstrate how climate warming and the disappearance of ice sheets during the early Holocene initiated eustatic sea-level rise that greatly modified the physiography of the Arctic Ocean. Sedimentation rates over the shelves and slopes were much greater during periods of rapid sea-level rise in the early and middle Holocene, as a result of the relative distance to the terrestrial sediment sources. However, estimates of suspended sediment delivery through major Arctic rivers do not indicate enhanced delivery during this time, which suggests enhanced rates of coastal erosion. The increased supply of terrigenous material to the outer shelves and deep Arctic Ocean in the early and middle Holocene might serve as analogous to forecast changes in the future Arctic.

Directionality of the ambient noise field in an Arctic, glacial bay

The directionality of ambient noise in an Arctic tidewater glacier bay was measured using two horizontally spaced, broadband hydrophones. Segments of noise were divided into two frequency bands and analyzed for arrival angle. These data show that different classes of source radiate noise in distinct spectral bands and are spatially diverse. A previously unidentified source, the interaction of surface gravity waves with underside of ice ledges at the periphery of icebergs, is described. The generation of noise by ice-wave interaction suggests that surface waves should be measured if ambient noise is to be used to monitor ice dynamics in glacial fjords.

Multibeam Bathymetry and Slope Stability of Isvika Bay, Murchisonfjorden, Nordaustlandet

A research expedition to the polar region of Murchisonfjorden (Nordaustlandet, Svalbard) on the research vessel Horyzont II took place in August 2009. This paper presents results from an extensive bathymetric measurement campaign of the Isvika Bay, southern part of Murchisonfjorden. The aim of this campaign was to select optimal sites for sediment sampling. A detailed analysis of the bathymetric features is performed with a special emphasis on the slope stability conditions. A simple method for identifying areas of sediment redeposition is proposed. The results confirm that the Isvika Bay has two distinct basins separated by a ridge. Both basins display flat central regions surrounded by steep slopes with gullies. In addition, results of analysed Quaternary geological data have indicated that the area was affected by ice repeated glacial activity in the past and that there is no morphological form typical for glacier erosion and sedimentation.

The impact of glacier meltwater on the underwater noise field in a glacial bay

Ambient noise oceanography is proving to be an efficient and effective tool for the study of ice-ocean interactions in the bays of marine-terminating glaciers. However, obtaining quantitative estimates of ice melting or calving processes from ambient noise requires an understanding of how sound propagation through the bay attenuates and filters the noise spectrum. Measurements of the vertical structure in sound speed in the vicinity of the Hans Glacier in Hornsund Fjord, Spitsbergen, made with O(130) CTD casts between May and November 2015, reveal high-gradient, upward-refracting sound speed profiles created by cold, fresh meltwater during summer months. Simultaneous recordings of underwater ambient noise made at depths of 1, 10 and 20 meters in combination with propagation model calculations using the model Bellhop illustrate the dominant role these surface ducts play in shaping the underwater soundscape. The surface ducts lead to a higher intensity and greater variability of acoustic energy in the near-surface layer covered by glacially-modified waters relative to deeper waters, indicating deeper zones as most appropriate for inter-seasonal acoustic monitoring of the glacial melt. Surface waveguides in Hornsund are relatively shallow and trap sound above O(1 kHz). Deeper waveguides observed elsewhere will also trap low-frequency sounds, such as those generated by calving events for example. Finally, the ambient noise field in Hornsund is shown to be strongly dependent on the distribution of ice throughout the bay, stressing the importance of performing complementary environmental measurements when interpreting the results of acoustic surveys. This article is protected by copyright. All rights reserved.

Statistical Analysis of Topography of Isvika Bay, Murchisonfjorden, Svalbard

We present a systematic study of the topography of Isvika Bay located in Murchisonfjorden, Svalbard. The very detailed statistical analysis based on the acoustic measurements is performed. Cell maps of the mean elevation, variance, skewness, and kurtosis are presented. The analyzed data suggest that the Isvika surface represents the Gaussian as well as non-Gaussian random fields. Similarity between the slope-gradient map and the map of the second statistical moment of elevations, which is presented in the logarithmic scale, is also considered. The characteristic landforms and their connection to values of skewness and kurtosis coefficients for the exemplary profile are also shown.

Contemporary sedimentation in the forefield of Hornbreen,Hornsund

Abstract The paper presents a model of contemporary sedimentation in the forefield of Hornbreen, tidewater glacier in Brepollen. The model is based on the results of grain-size analyses of bottom sediments and the information about dominant sedimentary processes in glaciated fjords. It is concluded that apart from the tidewater glacier which is the main source of sediment in this area, the material is transported also from the shores. Subsequently, the material is redeposited by iceberg-caused reworking, slides and gravity flows. Strong decreasing trend of particles’ diameters with increasing distance from the ice cliff is observed.

Submarine geomorphology at the front of the retreating Hansbreen tidewater glacier, Hornsund fjord, southwest Spitsbergen

ABSTRACT A 1:10,000 scale bathymetric map as well as 1:20,000 scale backscattering and geomorphological maps of two bays Isbjørnhamna and Hansbukta in the Hornsund fjord (Spitsbergen) present the submarine relief that was primarily formed during and after the retreat of the Hansbreen tidewater glacier. Geomorphological mapping was performed using multibeam bathymetric data and seismoacoustic profiling. The identified landforms include two types of transverse ridges interpreted as terminal and annual moraines, flat areas that are depressions filled with glaciomarine sediments, iceberg-generated pits and ploughmarks, pockmarks and fields of megaripples. Most of the identified landforms are genetically related to the retreat of Hansbreen since the termination of the Little Ice Age at the beginning of the twentieth century. Although Hansbreen has been speculated to be a surge-type glacier, no evidence of surging was identified in the submarine landform assemblage, which is in accordance with the absence of historically documented surges for that period.

Application of Passive Hydroacoustics in the Studies of Sea-Ice, Icebergs and Glaciers: Issues, Approaches and Future Needs

Arctic and Southern Oceans are extremely noisy places. Various geophysical and biological processes generate underwater sounds at different frequencies. Using spectral, wavelet and statistical analysis, it becomes possible to distinguish almost all individual phenomena. This allows the assessment of, among other things, the rainfall intensity, various characteristics of wind-generated waves, abundance of marine organisms and shipping traffic. These issues are now relatively well-understood. What is more, for such studies hydroacoustic methods have been widely used for many years and provided satisfactory results. In the last decades, however, more and more attention is paid to sea-ice processes and properties, calving events and drifting icebergs. Melting ice and retreating tidewater glaciers are also sources of underwater ambient noise. This becomes more and more noticeable due to the observed climate shifts. Dynamic nature of these phenomena and harsh conditions encountered during field measurements still limit the progress in this area of research. In spite of all, recent preliminary studies show the possibility of using passive acoustic methods for both analyzing calving events in the Arctic fjords and investigating the behavior of icebergs. It became possible, for instance, to identify and describe various stages of calving processes: large rumbles, ice fractures, impacts on the water and iceberg oscillations. On the other hand, ambient noise related with freshwater outflows and sound propagation in the vicinity of glaciers are still unstudied. Moreover, underwater sounds associated with sea-ice processes occurring in small basins are also poorly understood, as well as their directivity and relationships with meteorological and oceanographic conditions. These topics require further investigation, which will enable the development of appropriate classification algorithms. For this purpose, new field experiments and methods of data analysis as well as state-of-the-art measuring devices are needed. A review of existing research articles concerning underwater cryogenic sounds is presented here, supplemented by a summary of the main gaps and suggested future needs. All papers are sorted thematically and chronologically, showing the historical development of hydroacoustic methods and approaches in this area.

Studying melting icebergs with ambient noise oceanography

Marine-terminating glaciers are retreating at an unprecedented pace, largely as a result of enhanced submarine melting. However, studying ice-ocean interactions is complicated due to both harsh conditions prevailing in glacial bays and lack of scientific methods enabling continuous measurements. Recent studies have shown that high underwater noise levels measured in the Arctic are related to glacier melt, but quantitative research requires proper separation of individual noise sources, including icebergs and glacier fronts. Therefore, we show results of field experiments carried out in 2013, 2015, and 2016 in Hornsund fjord, Svalbard, to present directionality and statistics of the noise produced by melting icebergs. Measurements of noise directionality were conducted with 3-hydrophone acoustic array. Calculated angles of arrivals for the noise at the frequency range of 1–10 kHz correspond well to locations of individual, grounded icebergs. The amplitude of sound emitted by these sources has a symmetric α...