Co-seismic eruption and intermittent turbulence of a subglacial discharge plume revealed by continuous subsurface observations in Greenland

Abstract

In the Arctic, subglacial discharge plumes have been recently recognised as a key driver of fjord-scale circulation. However, owing to the danger that accompanies prolonged observations at plumes, no time-series data are available. Here, we present results showing the chaotic and irregular dynamics of a plume revealed by continuous subsurface monitoring directly on the calving front of a Greenlandic glacier. We found intense fluctuations in the current and scalars (temperature and salinity), recognised shallow and deep tidal modulation and anomalies due to co-seismic drainage of an ice-dammed lake via the plume, and observed rapid and marked changes in stratification. Our analysis uncovers energy cascade intermittency with coherent structures, corresponding to upwelling pulses of warm water. Prior to our research, in situ evidence of time-variable plume dynamics was absent and limited to snapshots, therefore, our study and approach will enable researchers to transition from an episodic view of a plume to a continuously updated image.

Solid-phase Mn speciation in suspended particles along meltwater-influenced fjords of West Greenland

“…Yet additional work is required to fully understand 1) the role and type of Mn(II) oxidizers, if present, in DI fjord and/or 2) the unique conditions favouring the presence of a Mn(IV) plume in DI fjord that are not present in the other investigated transects. One further potential caveat is that inner-fjord environments are dynamic interfaces in which ambient conditions, such as turbidity and water column structure, change markedly on both short-term (hours to days) and long-term (seasonal-interannual) timescales (Svendsen et al, 2002;De Andrés et al, 2020;Podolskiy et al, 2021). It therefore also remains an open question whether the Mn(IV) plume observed in DI fjord is a sustained feature, a seasonally recurring feature, or a sporadic feature appearing intermittently.…”

Strange attractor of a narwhal (Monodon monoceros)

“…To recognize the dominant timescales in diving behavior, we computed continuous 1D wavelet transfer (Fig. S1) using the Morse wavelet (Matlab default) [45, 46] (and references within). Results are shown as a movie together with embedding results (Video S1).…”

“…The state–space reconstruction of the underlying attractor was made via classical time-delay embedding [20]: where τ is time-delay and m is embedding dimension. To find appropriate embedding parameters we computed self-mutual information ( I ), autocorrelation ( R ), and false-negative neighbours ( FNN ) [46–48]. Furthermore, to reveal the time-varying variance of these estimates, we parsed the data into 6 h non-overlapping segments, computed the corresponding statistical features, and presented each result together with global median values (Fig.…”

Effects of the glacial meltwater supply on carbonate chemistry in Bowdoin Fjord, Northwestern Greenland

“…We interpreted this patch to be a plume of turbid water that visibly rises toward the fjord surface near the calving front of the glacier. This highly turbid patch is maintained free of sea ice by the upwelling subglacial discharge (Kanna et al, 2018;Podolskiy et al, 2021). In the summers of 2016 and 2017, sea ice began retreating from the fjord in mid-July and had disappeared by the end of July.…”

“…Therefore, DIC and TA components were added to the fjord water, either as a result of the dissolution of minerals such as calcium carbonate and the decomposition of organic matter occurring within the fjord waters, as described above, or as a result of mineral dissolution and organic matter decomposition occurring in the glacial meltwater before it flowed into the fjord. Podolskiy et al (2021) estimated residence time near the calving front of the glacier to be about several days based on the time series of the surface water temperature. Therefore, we inferred that DIC and TA components were added by the glacial meltwater affected by the dissolution of minerals such as calcium carbonate and the decomposition of organic matter before it flowed into the fjord.…”