Elymus athericus encroachment in Wadden Sea salt marshes is driven by surface‐elevation change

AbstractStrong disciplinary academic fragmentation and sectoral division in policies lead to problems regarding the management of landscapes. As a result, there is a focus on the preservation and development of either cultural or natural landscapes. We argue that framing landscapes as “natural” or “cultural” will not help sustainable management. The goal of this paper is to show that even what is referred to as nature, virtually always features an intricate combination of physical geography, biology, and cultural history. It provides an analytical framework that visualizes the three forces at play in physical landscapes. Therefore, we introduce a diachronic triangular approach to study and manage landscapes from a holistic point of view, allowing an exchange of different perspectives. To test this approach, we have applied our model to a diachronic case study on Wadden Sea salt marshes. That area has been influenced by physical-geographical, biological, and cultural landscape forces, which are still visible in the landscape to a large extent. By placing different landscape zones in the triangular concept for different time periods, we can identify and visualize these driving forces through time for this specific landscape. These all play their specific roles in the appearance of the landscape over time in a close mutual interconnection. More importantly, we show that the diverse and complex interplay between these forces makes the current-day landscape what it is. We therefore conclude that the diachronic triangular approach provides a conceptual tool to define and operationalize landscape management in the Wadden Sea area. We welcome similar approaches in other landscapes to assess the usefulness of the diachronic triangular landscape approach.

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Heterogeneous spatial and temporal pattern of surface elevation change and mass balance of the Patagonian ice fields between 2000 and 2016

The Cryosphere ◽

10.5194/tc-13-2511-2019 ◽

2019 ◽

Vol 13 (9) ◽

pp. 2511-2535 ◽

Cited By ~ 5

Author(s):

Wael Abdel Jaber ◽

Helmut Rott ◽

Dana Floricioiu ◽

Jan Wuite ◽

Nuno Miranda

Keyword(s):

Spatial Pattern ◽

Mass Balance ◽

Temporal Trend ◽

Sar Interferometry ◽

Surface Elevation ◽

Radar Signal ◽

Elevation Change ◽

Mass Losses ◽

Digital Elevation ◽

Surface Elevation Change

Abstract. The northern and southern Patagonian ice fields (NPI and SPI) have been subject to accelerated retreat during the last decades, with considerable variability in magnitude and timing among individual glaciers. We derive spatially detailed maps of surface elevation change (SEC) of NPI and SPI from bistatic synthetic aperture radar (SAR) interferometry data of the Shuttle Radar Topography Mission (SRTM) and TerraSAR-X add-on for Digital Elevation Measurements (TanDEM-X) for two epochs, 2000–2012 and 2012–2016, and provide data on changes in surface elevation and ice volume for the individual glaciers and the ice fields at large. We apply advanced TanDEM-X processing techniques allowing us to cover 90 % and 95 % of the area of NPI and 97 % and 98 % of SPI for the two epochs, respectively. Particular attention is paid to precisely co-registering the digital elevation models (DEMs), accounting for possible effects of radar signal penetration through backscatter analysis and correcting for seasonality biases in case of deviations in repeat DEM coverage from full annual time spans. The results show a different temporal trend between the two ice fields and reveal a heterogeneous spatial pattern of SEC and mass balance caused by different sensitivities with respect to direct climatic forcing and ice flow dynamics of individual glaciers. The estimated volume change rates for NPI are -4.26±0.20 km3 a−1 for epoch 1 and -5.60±0.74 km3 a−1 for epoch 2, while for SPI these are -14.87±0.52 km3 a−1 for epoch 1 and -11.86±1.99 km3 a−1 for epoch 2. This corresponds for both ice fields to an eustatic sea level rise of 0.048±0.002 mm a−1 for epoch 1 and 0.043±0.005 mm a−1 for epoch 2. On SPI the spatial pattern of surface elevation change is more complex than on NPI and the temporal trend is less uniform. On terminus sections of the main calving glaciers of SPI, temporal variations in flow velocities are a main factor for differences in SEC between the two epochs. Striking differences are observed even on adjoining glaciers, such as Upsala Glacier, with decreasing mass losses associated with slowdown of flow velocity, contrasting with acceleration and increase in mass losses on Viedma Glacier.

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CryoSat-2 delivers monthly and inter-annual surface elevation change for Arctic ice caps

The Cryosphere Discussions ◽

10.5194/tcd-9-2821-2015 ◽

2015 ◽

Vol 9 (3) ◽

pp. 2821-2865 ◽

Cited By ~ 2

Author(s):

L. Gray ◽

D. Burgess ◽

L. Copland ◽

M. N. Demuth ◽

T. Dunse ◽

...

Keyword(s):

Snow Accumulation ◽

Surface Elevation ◽

Radar Altimeter ◽

Elevation Change ◽

Ice Caps ◽

Ice Cap ◽

Winter Snow ◽

Surface Elevation Change ◽

Devon Ice Cap ◽

Arctic Ice

Abstract. We show that the CryoSat-2 radar altimeter can provide useful estimates of surface elevation change on a variety of Arctic ice caps, on both monthly and yearly time scales. Changing conditions, however, can lead to a varying bias between the elevation estimated from the radar altimeter and the physical surface due to changes in the contribution of subsurface to surface backscatter. Under melting conditions the radar returns are predominantly from the surface so that if surface melt is extensive across the ice cap estimates of summer elevation loss can be made with the frequent coverage provided by CryoSat-2. For example, the average summer elevation decreases on the Barnes Ice Cap, Baffin Island, Canada were 2.05 ± 0.36 m (2011), 2.55 ± 0.32 m (2012), 1.38 ± 0.40 m (2013) and 1.44 ± 0.37 m (2014), losses which were not balanced by the winter snow accumulation. As winter-to-winter conditions were similar, the net elevation losses were 1.0 ± 0.2 m (winter 2010/2011 to winter 2011/2012), 1.39 ± 0.2 m (2011/2012 to 2012/2013) and 0.36 ± 0.2 m (2012/2013 to 2013/2014); for a total surface elevation loss of 2.75 ± 0.2 m over this 3 year period. In contrast, the uncertainty in height change results from Devon Ice Cap, Canada, and Austfonna, Svalbard, can be up to twice as large because of the presence of firn and the possibility of a varying bias between the true surface and the detected elevation due to changing year-to-year conditions. Nevertheless, the surface elevation change estimates from CryoSat for both ice caps are consistent with field and meteorological measurements. For example, the average 3 year elevation difference for footprints within 100 m of a repeated surface GPS track on Austfonna differed from the GPS change by 0.18 m.

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Surface elevation change and mass balance of Icelandic ice caps derived from swath mode CryoSat-2 altimetry

Geophysical Research Letters ◽

10.1002/2016gl071485 ◽

2016 ◽

Vol 43 (23) ◽

pp. 12,138-12,145 ◽

Cited By ~ 32

Author(s):

L. Foresta ◽

N. Gourmelen ◽

F. Pálsson ◽

P. Nienow ◽

H. Björnsson ◽

...

Keyword(s):

Mass Balance ◽

Surface Elevation ◽

Elevation Change ◽

Ice Caps ◽

Surface Elevation Change

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Glacier mass-balance determination by remote sensing and high-resolution modelling

Journal of Glaciology ◽

10.3189/172756500781833016 ◽

2000 ◽

Vol 46 (154) ◽

pp. 491-498 ◽

Cited By ~ 28

Author(s):

Alun Hubbard ◽

Ian Willis ◽

Martin Sharp ◽

Douglas Mair ◽

Peter Nienow ◽

...

Keyword(s):

Remote Sensing ◽

Mass Balance ◽

Mass Flux ◽

Surface Elevation ◽

Surface Velocity ◽

Elevation Change ◽

Flux Divergence ◽

Flow Modelling ◽

Surface Elevation Change ◽

Divergence Field

AbstractAn indirect methodology for determining the distribution of mass balance at high spatial resolution using remote sensing and ice-flow modelling is presented. The method, based on the mass-continuity equation, requires two datasets collected over the desired monitoring interval: (i) the spatial pattern of glacier surface-elevation change, and (ii) the mass-flux divergence field. At Haut Glacier d’Arolla, Valais, Switzerland, the mass-balance distribution between September 1992 and September 1993 is calculated at 20 m resolution from the difference between the pattern of surface-elevation change derived from analytical photogrammetry and the mass-flux divergence field determined from three-dimensional, numerical flow modelling constrained by surface-velocity measurements. The resultant pattern of mass balance is almost totally negative, showing a strong dependence on elevation, but with large localized departures. The computed distribution of mass balance compares well (R2 = 0.91) with mass-balance measurements made at stakes installed along the glacier centre line over the same period. Despite the highly optimized nature of the flow-modelling effort employed in this study, the good agreement indicates the potential this method has as a strategy for deriving high spatial and temporal-resolution estimates of mass balance.

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Net Budget and Flow of South Cascade Glacier, Washington

Journal of Glaciology ◽

10.1017/s0022143000018608 ◽

1965 ◽

Vol 5 (41) ◽

pp. 547-566 ◽

Cited By ~ 78

Author(s):

Mark F. Meier ◽

W. V. Tangborn

Keyword(s):

Steady State ◽

Surface Elevation ◽

Elevation Change ◽

Glacier Surface ◽

Surface Elevation Change ◽

Long Valley ◽

Valley Glacier ◽

Ice Velocity ◽

The Mean ◽

Velocity Averages

AbstractIce velocity, net mass budget and surface elevation change data were collected over the length and width of a small (3.4 km. long) valley glacier from 1957 to 1964. Ice velocities range up to about 20 m./yr.; three prominent velocity maxima along the length of the glacier correspond to maxima in surface slope. Net mass budgets averaged over the glacier surface range between − 3.3 m. of water equivalent (1957–58) and +1.2 m. (1963–64). Except for the year 1960–61, curves of net budget versus altitude are parallel. During the period 1958–61 the glacier became thinner at a rate averaging 0.93 m./yr. The net budget and thinning data are internally consistent. Relations between emergence velocity, net budget and surface elevation change are examined at four specific points on the glacier surface and as functions of distance along the length of the glacier. Emergence velocity averages about −0.5 m. in the upper part of the glacier and about +1.0 m. in the lower part. Ice discharge and ice thickness are also calculated as functions of distance. The discharge reaches a peak of 8.8 × 105m.3of ice per year 2.2 km. from the head of the glacier. The mean thickness of the glacier is about 83 m. A steady-state distribution of net budget is used to calculate a steady-state discharge, which is 2.2 times larger than the present discharge.

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Antarctic firn compaction rates from repeat-track airborne radar data: I. Methods

Annals of Glaciology ◽

10.3189/2015aog70a203 ◽

2015 ◽

Vol 56 (70) ◽

pp. 155-166 ◽

Cited By ~ 16

Author(s):

B. Medley ◽

S.R.M. Ligtenberg ◽

I. Joughin ◽

M.R. Van den Broeke ◽

S. Gogineni ◽

...

Keyword(s):

Accumulation Rate ◽

Radar Data ◽

Temporal Variations ◽

Mass Change ◽

Surface Elevation ◽

Elevation Change ◽

Compaction Rate ◽

Thickness Change ◽

Surface Elevation Change ◽

Spatio Temporal

AbstractWhile measurements of ice-sheet surface elevation change are increasingly used to assess mass change, the processes that control the elevation fluctuations not related to ice-flow dynamics (e.g. firn compaction and accumulation) remain difficult to measure. Here we use radar data from the Thwaites Glacier (West Antarctica) catchment to measure the rate of thickness change between horizons of constant age over different time intervals: 2009–10, 2010–11 and 2009–11. The average compaction rate to ~25 m depth is 0.33 m a−1, with largest compaction rates near the surface. Our measurements indicate that the accumulation rate controls much of the spatio-temporal variations in the compaction rate while the role of temperature is unclear due to a lack of measurements. Based on a semi-empirical, steady-state densification model, we find that surveying older firn horizons minimizes the potential bias resulting from the variable depth of the constant age horizon. Our results suggest that the spatio-temporal variations in the firn compaction rate are an important consideration when converting surface elevation change to ice mass change. Compaction rates varied by up to 0.12 m a−1 over distances <6 km and were on average >20% larger during the 2010–11 interval than during 2009–10.

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