Subglacial hydrology at Rink Isbræ, West Greenland inferred from sediment plume appearance

ABSTRACTMarine-terminating outlet glaciers discharge most of the Greenland ice sheet's mass through frontal ablation and meltwater runoff. While calving can be estimated by in situ and remote sensing observations, submarine melting and subglacial meltwater transport are more challenging to quantify. Here we investigate the subglacial hydrology of Rink Isbræ, a fast-flowing West Greenland tidewater glacier, using time-lapse photography, modeled runoff estimates and daily satellite imagery from 2007 to 2011. We find that sediment plumes appear episodically at four distinct locations across the terminus, and last between 2 h and 17 d. This suggests short-term variability in discharge and the existence of persistent pathways. The seasonal onset of sediment plumes occurs before supraglacial lake drainages, shortly after the onset of runoff, and only after the wintertime ice mélange has begun disintegrating. Plumes were also visible after the cessation of runoff (23 ± 5 d), which is indicative of subglacial storage. The lack of either a seasonal velocity change or a correspondence between meltwater availability and plume occurrence suggests that the subglacial system persists in a state of inefficient drainage. Subglacial hydrology at tidewater glaciers is of critical importance in understanding dynamics at the ice front.

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Sediment plumes as a proxy for local ice-sheet runoff in Kangerlussuaq Fjord, West Greenland

Journal of Glaciology ◽

10.3189/002214310794457227 ◽

2010 ◽

Vol 56 (199) ◽

pp. 813-821 ◽

Cited By ~ 32

Author(s):

Daniel McGrath ◽

Konrad Steffen ◽

Irina Overeem ◽

Sebastian H. Mernild ◽

Bent Hasholt ◽

...

Keyword(s):

River Discharge ◽

Water Storage ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

West Greenland ◽

Meltwater Runoff ◽

Moderate Resolution ◽

Resolution Imaging ◽

Moderate Resolution Imaging Spectroradiometer

AbstractMeltwater runoff is an important component of the mass balance of the Greenland ice sheet (GrIS) and contributes to eustatic sea-level rise. In situ measurements of river runoff at the ˜325 outlets are nonexistent due to logistical difficulties. We develop a novel methodology using satellite observations of sediment plumes as a proxy for the onset, duration and volume of meltwater runoff from a basin of the GrIS. Sediment plumes integrate numerous poorly constrained processes, including meltwater refreezing and supra- and englacial water storage, and are formed by meltwater that exits the GrIS and enters the ocean. Plume characteristics are measured in Moderate Resolution Imaging Spectroradiometer (MODIS, band 1, 250 m) satellite imagery during the 2001-08 melt seasons. Plume formation and cessation in Kangerlussuaq Fjord, West Greenland, are positively correlated (r2 = 0.88, n = 5, p < 0.05; r2 = 0.93, n = 5, p < 0.05) with ablation onset and cessation at the Kangerlussuaq Transect automatic weather station S5 (490 ma.s.l., 6 km from the ice margin). Plume length is positively correlated (r2 = 0.52, n = 35, p < 0.05) with observed 4 day mean Watson River discharge throughout the 2007 and 2008 melt seasons. Plume length is used to infer instantaneous and annual cumulative Watson River discharge between 2001 and 2008. Reconstructed cumulative discharge values overestimate observed cumulative discharge values for 2007 and 2008 by 15% and 29%, respectively.

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Feeding rates of abyssal scavenging amphipods (Eurythenes gryllus) determined in situ by time-lapse photography

Deep Sea Research Part A Oceanographic Research Papers ◽

10.1016/0198-0149(85)90090-1 ◽

1985 ◽

Vol 32 (4) ◽

pp. 443-450 ◽

Cited By ~ 33

Author(s):

B.T. Hargrave

Keyword(s):

Time Lapse ◽

Feeding Rates ◽

Time Lapse Photography

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Contribution of calving to frontal ablation quantified from seismic and hydroacoustic observations calibrated with lidar volume measurements

10.5194/tc-2019-75 ◽

2019 ◽

Author(s):

Andreas Köhler ◽

Michał Pętlicki ◽

Pierre-Marie Lefeuvre ◽

Giuseppa Buscaino ◽

Christopher Nuth ◽

...

Keyword(s):

Temporal Resolution ◽

Seismic Station ◽

Time Lapse ◽

High Temporal Resolution ◽

Tidewater Glaciers ◽

Relative Contribution ◽

Glacier Front ◽

Volume Measurements ◽

Seismic Records ◽

Frontal Ablation

Abstract. Frontal ablation contributes significantly to the mass balance of tidewater glaciers in Svalbard and can be recovered with high temporal resolution using continuous seismic records. Determination of the relative contribution of dynamic ice loss through calving to frontal ablation requires precise estimates of calving volumes at the same temporal resolution. We combine seismic and hydroacoustic observations close to the calving front of Kronebreen, a marine terminating glacier in Svalbard, with repeat lidar scanning of the glacier front. Simultaneous time-lapse photography is used to assign volumes measured from lidar scans to seismically detected calving events. Empirical models derived from signal properties such as integrated amplitude are able to replicate volumes of individual calving events and cumulative subaerial ice loss over different lidar scan intervals from seismic and hydroacoustic data alone. This enables quantification of the contribution of calving to frontal ablation, which we estimate for Kronebreen to be about 18–30 %, slightly below the subaerially exposed area of the glacier front. We further develop a model calibrated for the permanent seismic station KBS at about 15 km distance from the glacier front, where 15–60 % of calving events can be detected under variable noise conditions due to reduced signal amplitudes at distance. Between 2007 and 2017, we find a 5–30 % contribution of calving ice blocks to frontal ablation which emphasizes the importance of underwater melting (roughly 150–350 m a−1). This study shows the feasibility to seismically monitor not only frontal ablation rates but also its dynamic ice loss contribution continuously and at high temporal resolution.

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Effects of dead conspecifics, hunger states, and seasons on the foraging behavior of the purple urchin Heliocidaris crassispina

10.1101/2020.03.09.984674 ◽

2020 ◽

Author(s):

Dominic Franco C. Belleza ◽

Yuuki Kawabata ◽

Tatsuki Toda ◽

Gregory N. Nishihara

Keyword(s):

Foraging Behavior ◽

Field Experiments ◽

Prey Species ◽

Sea Urchins ◽

Time Lapse ◽

Aquatic Environments ◽

Feeding Rates ◽

Avoidance Behaviors ◽

Time Lapse Photography

ABSTRACTTrophic cascades exerts a powerful effect between predator and prey relationships in an ecosystem. In aquatic environments, the signals associated with predators and predation are used by prey as a cue to avoid encountering predators when foraging for food. These cues are powerful enough to control prey populations and indirectly protect primary producers. We evaluated the effects of cues associated with predation on the purple urchin, Heliocidaris crassispina and examined effects of hunger state and season using time-lapse photography, we conducted a series of manipulative and in situ behavior experiments to determine foraging behavior patterns which demonstrate behavior modification. The results suggest that starved urchins were less sensitive to predation cues when compared to normally fed urchins. Field experiments indicated that 70% of fed urchins fled when exposed to a predation cue (presence of a dead urchin), whereas all starved urchins remained regardless of the cue, supporting the results from the laboratory using the dead urchin and algae treatment cues. Sea urchin activity and feeding rates were lower in winter-spring than in summer-autumn. We suggest that hunger state has a large influence over the behavioral-response of sea urchins, while also being affected by season due to metabolic control. In general, starvation overrides predator avoidance behaviors and exposes prey species to higher risks of predation.

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Contribution of calving to frontal ablation quantified from seismic and hydroacoustic observations calibrated with lidar volume measurements

The Cryosphere ◽

10.5194/tc-13-3117-2019 ◽

2019 ◽

Vol 13 (11) ◽

pp. 3117-3137 ◽

Cited By ~ 7

Author(s):

Andreas Köhler ◽

Michał Pętlicki ◽

Pierre-Marie Lefeuvre ◽

Giuseppa Buscaino ◽

Christopher Nuth ◽

...

Keyword(s):

Temporal Resolution ◽

Time Lapse ◽

High Temporal Resolution ◽

Tidewater Glaciers ◽

Relative Contribution ◽

Glacier Front ◽

Volume Measurements ◽

Seismic Records ◽

Frontal Ablation

Abstract. Frontal ablation contributes significantly to the mass balance of tidewater glaciers in Svalbard and can be recovered with high temporal resolution using continuous seismic records. Determination of the relative contribution of dynamic ice loss through calving to frontal ablation requires precise estimates of calving volumes at the same temporal resolution. We combine seismic and hydroacoustic observations close to the calving front of Kronebreen, a marine-terminating glacier in Svalbard, with repeat lidar scanning of the glacier front. Simultaneous time-lapse photography is used to assign volumes measured from lidar scans to seismically detected calving events. Empirical models derived from signal properties such as integrated amplitude are able to replicate volumes of individual calving events and cumulative subaerial ice loss over different lidar scan intervals from seismic and hydroacoustic data alone. This enables quantification of the contribution of calving to frontal ablation, which we estimate for Kronebreen to be about 18 %–30 %, slightly below the subaerially exposed area of the glacier front. We further develop a model calibrated for the permanent seismic Kings Bay station (KBS) at about 15 km distance from the glacier front, where 15 %–60 % of calving events can be detected under variable noise conditions due to reduced signal amplitudes at distance. Between 2007 and 2017, we find a 5 %–30 % contribution of calving ice blocks to frontal ablation, which emphasizes the importance of underwater melting (roughly 4–9 m d−1). This study shows the feasibility to seismically monitor not only frontal ablation rates but also the dynamic ice loss contribution continuously and at high temporal resolution.

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Influence of glacier runoff and near-terminus subglacial hydrology on frontal ablation at a large Greenlandic tidewater glacier

Journal of Glaciology ◽

10.1017/jog.2020.109 ◽

2020 ◽

pp. 1-10

Author(s):

Charlie Bunce ◽

Peter Nienow ◽

Andrew Sole ◽

Tom Cowton ◽

Benjamin Davison

Keyword(s):

High Frequency ◽

Greenland Ice Sheet ◽

Time Lapse ◽

Temporal Variations ◽

Hydraulic Efficiency ◽

Tidewater Glaciers ◽

Total Mass Loss ◽

Glacier Runoff ◽

Iceberg Calving ◽

Frontal Ablation

Abstract Frontal ablation from tidewater glaciers is a major component of the total mass loss from the Greenland ice sheet. It remains unclear, however, how changes in atmospheric and oceanic temperatures translate into changes in frontal ablation, in part due to sparse observations at sufficiently high spatial and temporal resolution. We present high-frequency time-lapse imagery (photos every 30 min) of iceberg calving and meltwater plumes at Kangiata Nunaata Sermia (KNS), southwest Greenland, during June–October 2017, alongside satellite-derived ice velocities and modelled subglacial discharge. Early in the melt season, we infer a subglacial hydrological network with multiple outlets that would theoretically distribute discharge and enhance undercutting by submarine melt, an inference supported by our observations of terminus-wide calving during this period. During the melt season, we infer hydraulic evolution to a relatively more channelised subglacial drainage configuration, based on meltwater plume visibility indicating focused emergence of subglacial water; these observations coincide with a reduction in terminus-wide calving and transition to an incised planform terminus geometry. We suggest that temporal variations in subglacial discharge and near-terminus subglacial hydraulic efficiency exert considerable influence on calving and frontal ablation at KNS.

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Effects of dead conspecifics, hunger states, and seasons on the foraging behavior of the purple urchin Heliocidaris crassispina

Marine Ecology Progress Series ◽

10.3354/meps13653 ◽

2021 ◽

Vol 664 ◽

pp. 133-148

Author(s):

DFC Belleza ◽

Y Kawabata ◽

T Toda ◽

GN Nishihara

Keyword(s):

Foraging Behavior ◽

Field Experiments ◽

Sea Urchins ◽

Time Lapse ◽

Feeding Rates ◽

Predator Prey ◽

Avoidance Behaviors ◽

Behavioral Cues ◽

Time Lapse Photography

Trophic cascades are a powerful result of predator-prey relationships in an ecosystem. In aquatic environments, the signals associated with predators and predation are used by prey as a cue to avoid encountering predators when foraging for food. These behavioral cues can be powerful enough to control prey populations and indirectly protect primary producers. Here, we evaluated the effects of cues associated with predation on the purple urchin Heliocidaris crassispina and examined effects of hunger state and season, using time-lapse photography. A series of laboratory and in situ manipulative experiments were conducted to determine patterns of foraging behavior and behavioral modifications. We showed that starved urchins were less sensitive to predation cues compared to normally fed urchins. Field experiments indicated that 70% of fed urchins fled when exposed to a predation cue (presence of a dead urchin) whereas starved urchins remained regardless of the cue, supporting results from the laboratory using dead urchin and algal cues. Sea urchin activity and feeding rates were lower in winter-spring than in summer-autumn. Results suggest that hunger state has a large influence over the behavioral response of sea urchins, while also being affected by season due to metabolic control. In general, starvation appears to override predator avoidance behaviors, which exposes prey species to higher risks of predation.

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Experimental study of the formation of the bulboventricular loop in the chick

Development ◽

10.1242/dev.27.3.623 ◽

1972 ◽

Vol 27 (3) ◽

pp. 623-637

Author(s):

Alfredo Castro-Quezada ◽

Bernardo Nadal-Ginard ◽

María V. de la Cruz

Keyword(s):

Electron Microscope ◽

Time Lapse ◽

Mirror Image ◽

Heart Tube ◽

Removal Experiments ◽

Atrioventricular Groove ◽

The Right ◽

Time Lapse Photography ◽

Made In

The formation of the normal bulboventricular loop (convex to the right) and the inverted loop (convex to the left) produced by the Lepori technique in chick embryos was studied. The development of the loops was recorded by means of diagrams, photographs and microscopic time-lapse photography. Electron-microscope studies were also made. The normal loop was studied by means of labelling and removal experiments on the heart tube. The results demonstrated that the fusion of both cardiac primordia is made in stage 9 — in the mid-line of the embryo and that the first asymmetry of the heart tube appears in stage 10. The truncus region developed in situ directed towards the right after the fusion of both cardiac primordia, and in this region the electron-microscope study demonstrated a gradient of caudo-cephalic differentiation. In stage 10 the left caudal groove is the prospective interventricular groove, but the right caudal groove is not the right atrioventricular groove as had been stated by others. The asymmetric incorporation of both primordia begins in stage 11 —, when the curvature of the loop is already developing. In the removal experiments it was evident that the different portions of the cardiac tube in situ are orientated in space independently of the whole of the loop. The formation of the experimentally inverted loop is a mirror-image of the normal loop and appears to be originated through mechanic traction of the cardiac tube by the left splachnopleure and not by a faster displacement of the right cardiac primordia.

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Homing behaviour by destructive crown-of-thorns starfish is triggered by local availability of coral prey

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2020.1341 ◽

2020 ◽

Vol 287 (1938) ◽

pp. 20201341

Author(s):

S. D. Ling ◽

Z.-L. Cowan ◽

J. Boada ◽

E. B. Flukes ◽

M. S. Pratchett

Keyword(s):

Time Lapse ◽

Directional Movement ◽

The Pacific ◽

Population Outbreaks ◽

Population Outbreak ◽

And Diffusion ◽

Daily Displacement ◽

Logistic Modelling ◽

Time Lapse Photography

Corallivorous crown-of-thorns starfishes ( Acanthaster spp.) can decimate coral assemblages on Indo-Pacific coral reefs during population outbreaks. While initial drivers of population irruptions leading to outbreaks remain largely unknown, subsequent dispersal of outbreaks appears coincident with depletion of coral prey. Here, we used in situ time-lapse photography to characterize movement of the Pacific crown-of-thorns starfish ( Acanthaster cf. solaris ) in the northern and southern Great Barrier Reef in 2015, during the fourth recorded population outbreak of the starfish, but prior to widespread coral bleaching. Daily tracking of 58 individuals over a total of 1117 h revealed all starfish to move a minimum of 0.52 m, with around half of all tracked starfish showing negligible daily displacement (less than 1 m day −1 ), ranging up to a maximum of 19 m day −1 . Movement was primarily nocturnal and daily displacement varied spatially with variation in local availability of Acropora spp., which is the preferred coral prey. Two distinct behavioural modes emerged: (i) homing movement, whereby tracked paths (as tested against a random-walk-model) involved short displacement distances following distinct ‘outward' movement to Acropora prey (typically displaying ‘feeding scars') and ‘homebound' movement to nearby shelter; versus (ii) roaming movement, whereby individuals showed directional movement beyond initial tracking positions without return. Logistic modelling revealed more than half of all tracked starfish demonstrated homing when local abundance (percentage cover) of preferred Acropora coral prey was greater than 33%. Our results reveal facultative homing by Acanthaster with the prey-dependent behavioural switch to roaming forays providing a mechanism explaining localized aggregations and diffusion of these population irruptions as prey is locally depleted.

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