Nearby Glaciers Research Articles

Short-term time-series observations of phytoplankton light-absorption and productivity in Prydz Bay, coastal Antarctica

The optical characteristics of coastal Antarctic waters exhibit complexity due to the dynamic hydrography influenced by meltwater intrusion, which alters nutrient levels, thermohaline structure, and optically active substances (OAS) regimes. Studies on bio-optical variability and its implications on phytoplankton productivity (PP) are scanty in coastal polar regions. On this backdrop, time-series measurements (72 h at 6 h intervals) of bio-optical properties such as phytoplankton biomass (chlorophyll-a), absorption (aph), and total suspended matter (TSM) concurrently with PP were measured to understand their interplay and variability in relation to the ambient physicochemical settings in the under-sampled Prydz Bay, coastal Antarctica. Our findings revealed thermohaline stratification within the bay, likely attributed to the inflow of less saline meltwater from nearby glaciers and minimal wind activity. The consistent presence of sub-surface chlorophyll maximum (SCM) beneath the stratified layer underscored the light-acclimatization response of shade-adapted phytoplankton. Surface waters exhibited higher TSM compared to deeper layers, indicating glacial melt influence, while the depth of the sunlit layer remained relatively stable, suggesting limited water mass movement and/or variability in OAS at the study site. An inverse relation between chlorophyll-a and chlorophyll-a-specific phytoplankton light absorption (a*ph(λ)) manifested ‘pigment package effect’ within the prevailing phytoplankton community, implying reduced light-absorption efficiency and consequent lower PP. Compared to chlorophyll-a, the phytoplankton light absorption (aph(λ)) emerged as a better proxy for explaining PP variability. Nutrient availability was not limiting, which was conducive to micro (large) phytoplankton growth. Classification of phytoplankton size classes (micro, nano, and pico) based on the B/R ratio (aph at Blue (443 nm)/Red (676 nm) region) confirmed the dominance of larger (micro) phytoplankton that are more susceptible to package effect, thus have implications on reduced PP potential of this polar marine ecosystem.

Meteorological drivers of melt at two nearby glaciers in the McMurdo Dry Valleys of Antarctica

Abstract We study the meteorological drivers of melt at two glaciers in Taylor Valley, Antarctica, using 22 years of weather station observations and surface energy fluxes. The glaciers are located only 30 km apart, but have different local climates; Taylor Glacier is generally drier and windier than Commonwealth Glacier, which receives more snowfall due to its proximity to the coast. Commonwealth Glacier shows more inter-annual melt variability, explained by variable albedo due to summer snowfall events. A significant increase in surface melt at Commonwealth Glacier is associated with a decrease in summer minimum albedo. Inter-annual variability in melt at both glaciers is linked to degree-days above freezing during föhn events, occurring more frequently at Taylor Glacier. At Taylor Glacier melt occurs most often with positive air temperatures, but föhn conditions also favour sublimation, which cools the surface and prevents melt for the majority of the positive air temperatures. At Commonwealth Glacier, most of the melt instead occurs with sub-zero air temperatures, driven by strong solar radiative heating. Future melt at Taylor Glacier will likely be more sensitive to changes in föhn events, while Commonwealth Glacier will be impacted more by changes in near coastal weather, where moisture inputs can drive cloud cover, snowfall and change albedo.

The importance of regional sea-ice variability for the coastal climate and near-surface temperature gradients in Northeast Greenland

Abstract. The climate in Northeast Greenland is shaped by complex topography and interaction with the cryosphere. Since the regional ecosystem processes are sensitive to atmospheric stability conditions, it is crucial to capture this complexity including adequate cryosphere coupling. This study uses an observational dataset from the Zackenberg region (Northeast Greenland) to investigate the local- and large-scale factors that determine the slope temperature gradient (STG), i.e., the temperature gradient along the mountain slope. A synthesis of automated weather stations, reanalysis, and a regional climate model simulations was used. For all seasons, our results show that snow cover and near-fjord ice conditions are the dominating factors governing the temporal evolution of the STG in the Zackenberg region. Considering large-scale drivers of the STG, we find that temperature inversions are associated with positive 500 hPa geopotential height and surface pressure anomalies over East Greenland. A strong connection between fractional sea-ice cover (SIF) in the Greenland Sea and the terrestrial climate of the Zackenberg region is found. A positive SIF anomaly coincides with a shallow STG, i.e., more positive (inversions) or less negative than the mean STG, since the temperature at the bottom of the valley decreases more than at the top. For example, the mean STG varies by ∼4 ∘C km−1 for a corresponding ∼27 % change in SIF. Reduction in temperature and precipitation (snowfall) during the days with high sea ice also affects the surface mass balance (SMB) of nearby glaciers and ice caps as shown for the A. P. Olsen Ice Cap. During summer, days with high SIF are associated with a positive SMB anomaly in the ablation area (∼16 mm w.e. d−1; indicating less melt) and a negative anomaly in the accumulation area (∼-0.3 mm w.e. d−1; indicating less accumulation). Based on our findings, we speculate that the local conditions in the Zackenberg region associated with anomalously low sea ice (i.e., a decrease in atmospheric stability) will be more prominent in the future with climate warming.

Heterogeneous changes of soil microclimate in high mountains and glacier forelands

Landscapes nearby glaciers are disproportionally affected by climate change, but we lack detailed information on microclimate variations that can modulate the impacts of global warming on proglacial ecosystems and their biodiversity. Here, we use near-subsurface soil temperatures in 175 stations from polar, equatorial and alpine glacier forelands to generate high-resolution temperature reconstructions, assess spatial variability in microclimate change from 2001 to 2020, and estimate whether microclimate heterogeneity might buffer the severity of warming trends. Temporal changes in microclimate are tightly linked to broad-scale conditions, but the rate of local warming shows great spatial heterogeneity, with faster warming nearby glaciers and during the warm season, and an extension of the snow-free season. Still, most of the fine-scale spatial variability of microclimate is one-to-ten times larger than the temporal change experienced during the past 20 years, indicating the potential for microclimate to buffer climate change, possibly allowing organisms to withstand, at least temporarily, the effects of warming.

Evolution of the dynamics of Airdrop Glacier, western Axel Heiberg Island, over a seven-decade-long advance

Various remotely sensed data, including historical aerial photographs, declassified intelligence satellite photographs, optical satellite imagery, and synthetic aperture radar data, were used to undertake the first comprehensive reconstruction of the dynamics of Airdrop Glacier on Axel Heiberg Island, Nunavut. Observations show a continuous terminus advance totalling ∼6 km since 1950 and notably less variability in its surface velocities in comparison to adjacent Iceberg Glacier. This advance is concurrent with relatively high flow rates over its entire surface, resulting in significant thickening near the terminus and thinning at higher elevations. Velocities have more than halved from the mid-2000s to 2021, but without any definitive evidence of previous flow instabilities, we cannot confirm whether Airdrop's behaviour is cyclic in nature and therefore characteristic of a surge. Instead, Airdrop Glacier could be experiencing a delayed response to the positive mass balance conditions of the Little Ice Age, which could also explain the advance of other nearby glaciers. Its recent slowdown could then be indicative of a gradual adjustment to recent climatic conditions. This study highlights the need for comprehensive studies of glacier dynamics in the Canadian Arctic to improve our understanding of the factors triggering dynamic instabilities and causing the observed variety of behaviours.

Reversible ice sheet thinning in the Amundsen Sea Embayment during the Late Holocene

Abstract. Cosmogenic-nuclide concentrations in subglacial bedrock cores show that the West Antarctic Ice Sheet (WAIS) at a site between Thwaites and Pope glaciers was at least 35 m thinner than present in the past several thousand years and then subsequently thickened. This is important because of concern that present thinning and grounding line retreat at these and nearby glaciers in the Amundsen Sea Embayment may irreversibly lead to deglaciation of significant portions of the WAIS, with decimeter- to meter-scale sea level rise within decades to centuries. A past episode of ice sheet thinning that took place in a similar, although not identical, climate was not irreversible. We propose that the past thinning–thickening cycle was due to a glacioisostatic rebound feedback, similar to that invoked as a possible stabilizing mechanism for current grounding line retreat, in which isostatic uplift caused by Early Holocene thinning led to relative sea level fall favoring grounding line advance.

A detection of the sea level fingerprint of Greenland Ice Sheet melt.

Rapid melting of ice sheets and glaciers drives a unique geometry, or fingerprint, of sea level change. However, the detection of individual fingerprints has been challenging because of sparse observations at high latitudes and the difficulty of disentangling ocean dynamic variability from the signal. We predict the fingerprint of Greenland Ice Sheet (GrIS) melt using recent ice mass loss estimates from radar altimetry data and model reconstructions of nearby glaciers and compare this prediction to an independent, altimetry-derived sea surface height trend corrected for ocean dynamic variability in the region adjacent to the ice sheet. A statistically significant correlation between the two fields (P < 0.001) provides an unambiguous observational detection of the near-field sea level fingerprint of recent GrIS melting in our warming world.

Anthropogenic influence on surface changes at the Olivares glaciers; Central Chile

We have investigated the source and role of light-absorbing impurities (LAIs) deposited on the glaciers of the Olivares catchment, in Central Chile. LAIs can considerably darken (lowered albedo) the glacier surface, enhancing their melt. We combined chemical and mineralogical laboratory analyses of surface and ice core samples with field-based spectral reflectance measurements to investigate the nature and properties of such LAIs. Using remote sensing-based albedo maps, we upscaled local information to glacier-wide coverage. We then used a model to evaluate the sensitivity of surface mass balance to a change in ice and snow albedo. The across-scale surface observations in combination with ice core analysis revealed a history of over half a century of LAIs deposition. We found traces of mining residuals in glacier surface samples. The glaciers with highest mass loss in the catchment present enhanced concentrations of surface dust particles with low reflectance properties. Our results indicate that dust particles with strong light-absorbing capacity have been mobilized from mine tailings and deposited on the nearby glacier surfaces. Large-scale assessment from satellite-based observations revealed darkening (ice albedo lowering) at most investigated glacier tongues from 1989 to 2018. Glacier melt is sensitive to ice albedo. We believe that an accelerated winter and spring snow albedo decrease, partially triggered by surface impurities, might be responsible for the above-average mass loss encountered in this catchment.

Evidence of glacial activity during MIS 4 in the Rocky Mountains, Colorado, USA

ABSTRACT The Ziegler Reservoir fossil site near Snowmass Village, Colorado, provides a rare opportunity to examine environmental conditions in the Rocky Mountains during marine isotope stage (MIS) 4 (71–57 ka). Although recognized as a global-scale cold event, MIS 4 is typically absent from Rocky Mountain glacial chronologies because the geologic evidence was covered or destroyed during the subsequent, and more extensive, MIS 2 (Pinedale; 29–14 ka) glaciation. Ziegler Reservoir lies beyond the Pinedale glacial extent, which allowed for the preservation of a long-lived sequence of eolian sediments deposited in a lacustrine environment that spans from late MIS 6 (ca. 140 ka) through early MIS 3 (ca. 55 ka). Sediments dating to MIS 4 exhibit a significant increase in clay-sized particles, suggesting that the source areas, most likely nearby glacio-fluvial deposits, were enriched with fine-grained material at that time. We hypothesize that the elevated clay content was the result of rock flour production by nearby valley glaciers that were active in the Rocky Mountains during MIS 4. The results of our study illustrate how recognizing indirect evidence of glacial activity can result in a more complete record of past climate conditions than what could be achieved by the study of moraines alone.

Coastal Bacterial Community Response to Glacier Melting in the Western Antarctic Peninsula.

Current warming in the Western Antarctic Peninsula (WAP) has multiple effects on the marine ecosystem, modifying the trophic web and the nutrient regime. In this study, the effect of decreased surface salinity on the marine microbial community as a consequence of freshening from nearby glaciers was investigated in Chile Bay, Greenwich Island, WAP. In the summer of 2016, samples were collected from glacier ice and transects along the bay for 16S rRNA gene sequencing, while in situ dilution experiments were conducted and analyzed using 16S rRNA gene sequencing and metatranscriptomic analysis. The results reveal that certain common seawater genera, such as Polaribacter, Pseudoalteromonas and HTCC2207, responded positively to decreased salinity in both the bay transect and experiments. The relative abundance of these bacteria slightly decreased, but their functional activity was maintained and increased the over time in the dilution experiments. However, while ice bacteria, such as Flavobacterium and Polaromonas, tolerated the increased salinity after mixing with seawater, their gene expression decreased considerably. We suggest that these bacterial taxa could be defined as sentinels of freshening events in the Antarctic coastal system. Furthermore, these results suggest that a significant portion of the microbial community is resilient and can adapt to disturbances, such as freshening due to the warming effect of climate change in Antarctica.

Land deformation monitoring using optical remote sensing and PS-InSAR technique nearby Gangotri glacier in higher Himalayas

In the present study, we have introduced a strategic technique for interrelating between slow land surface movement (SLSM) and land susceptibility (LS) map of a higher Himalayan region nearby Gangotri, India by integrating geospatial techniques based on modified frequency ratio technique acquired by optical remote sensing for LS mapping. On the other hand, PS-InSAR technique acquired by microwave remote sensing has been used for monitoring the SLSM. As SLSM is one of the major geological hazard susceptible for highly undulating terrain like Gangotri glacier basin in higher Himalaya which is also a most attractive tourist region in Uttarakhand, India. With the integration of this technology, it would be possible for monitoring SLSM and mapping LS of any hazardous area. PS-InSAR technique allows efficient planning by providing meticulous data about SLSM. PS-InSAR technique is used for monitoring SLSM in scale small within approximately millimetre range. Further, we have used SAR imageries of C band of ENVISAT satellite for the duration of March 2004–May 2007 for nearby Gangotri region. This work also comprises using satellite imageries of Landsat 7, Sentinel 2 and SRTM data for LS mapping purpose. The result shows that in the vicinity of the Gangotri region, the land surface movement was observed around 2 to 18 mm. Also, the study showed that the SLSM affected regions come under the High-risk zone of LS and vice versa.

A 36-Year Record of Rock Avalanches in the Saint Elias Mountains of Alaska, With Implications for Future Hazards

Glacial retreat and mountain-permafrost degradation resulting from rising global temperatures have the potential to impact the frequency and magnitude of landslides in glaciated environments. Several recent events, including the 2015 Taan Fiord rock avalanche, which triggered a tsunami with one of the highest wave runups ever recorded, have called attention to the hazards posed by landslides in regions like southern Alaska. In the Saint Elias Mountains, the presence of weak sedimentary and metamorphic rocks and active uplift resulting from the collision of the Yakutat and North American tectonic plates create landslide-prone conditions. To differentiate between the typical frequency of landsliding resulting from the geologic and tectonic setting of this region, and landslide processes that may be accelerated due to changes in climate, we used Landsat imagery to create an inventory of rock avalanches in a 3700 km2 area of the Saint Elias Mountains. During the period from 1984-2019, we identified 220 rock avalanches with a mean recurrence interval of 60 days. We compared our landslide inventory with a catalog of M ≥ 4 earthquakes to identify potential coseismic events, but only found three possible earthquake-triggered rock avalanches. We observed a distinct temporal cluster of 41 rock avalanches from 2013 through 2016 that correlated with above average air temperatures (including the three warmest years on record in Alaska, 2014-2016); this cluster was similar to a temporal cluster of recent rock avalanches in nearby Glacier Bay National Park and Preserve. The majority of rock avalanches initiated from bedrock ridges in probable permafrost zones, suggesting that ice loss due to permafrost degradation, as opposed to glacial thinning, could be a dominant factor contributing to rock-slope failures in the high elevation areas of the Saint Elias Mountains. Although earthquake-triggered landslides have episodically occurred in southern Alaska, evidence from our study suggests that area-normalized rates of non-coseismic rock avalanches were greater during the period from 1964 to 2019, and that the frequency of these events will continue to increase as the climate continues to warm. These findings highlight the need for hazard assessments in Alaska that address changes in landslide patterns related to climate change.

Distribution and sources of polycyclic aromatic hydrocarbons in the water column of Kongsfjorden, Arctic

Kongsfjorden is known for its characteristic multi-layer water mass formed by the convergence of freshwaters from nearby glaciers and rivers and saline water from the Atlantic and Arctic. The distribution of polycyclic aromatic hydrocarbons (PAHs) in the water column of Kongsfjorden was investigated and their potential sources were analyzed. The total concentrations of 16 PAHs in the surface seawater and river water were in the range of 33.4−79.8 ng/L (mean 48.5 ng/L) and 2.3−201.4 ng/L (mean 126.1 ng/L), respectively. Horizontally, PAHs were mainly concentrated around river estuaries and the glacier front in the dissolved phase. Vertically, the PAHs in the particulate phase followed surface-enrichment and depth-depletion patterns in most stations, with the maximum concentration found at 50 m depth in the central area of Kongsfjorden. The compositions of PAHs in seawater and rivers were similar, with two-ring and tricyclic PAHs comprising the majority of the dissolved and particulate phases. PAHs found in Kongsfjorden waters appeared to be derived from multiple sources such as petroleum and coal combustion. PAHs in the bay mouth of Kongsfjorden were mainly introduced by the West Spitsbergen Current and the Arctic waters, while in the inner bay, atmospheric deposition and local sources were the major contributors. The distribution of PAHs was mainly attributed to the suspended particulate distribution.

Holocene glacier behavior around the northern Antarctic Peninsula and possible causes

We obtained 49 new 10Be ages that document the activity of the former Northern Antarctic Peninsula Ice Sheet, and subsequently the James Ross Island Ice Cap and nearby glaciers, from the end of the last glacial period until the last ∼100 years. The data indicate that from >11 to ∼8 ka marked recession of glacier systems occurred around James Ross Island, including tidewater and local land-terminating glaciers. Glaciers reached heads of bays and fjords by 8-7 ka. Subsequently, local glaciers were larger than present around (at least) 7.5-7 ka and ∼5-4 ka, at times between 3.9 and 3.6 ka and just after 3 ka, between ∼2.4 and ∼1 ka, and from ∼300 to ∼100 years ago. After deglaciation, the largest local glacier extents occurred between ∼7 ka and ∼4 ka.Comparison with other paleoclimate records, including of sea ice extent, reveals coherent climate changes over ∼15° of latitude. In the early Holocene, most of the time a swath of warmth spanned from southern South America to the Antarctic Peninsula sector. We infer such intervals are times of weakening and/or poleward expansion of the band of stronger westerlies, associated with contraction of the polar vortex. Conversely, increased sea ice and equatorward expansion of the westerlies and the polar vortex favor larger glaciers from Patagonia to the Antarctic Peninsula, which typically occurred after ∼8 ka, although warm stretches did take place. For example, on the Antarctic Peninsula and in Patagonia the interval from 4 to ∼3 ka was typically warm, but conditions were not uniform in either region. We also infer that reduced and expanded glacier extents in Patagonia and the eastern Antarctic Peninsula tend to occur when conditions resemble a persistent positive and negative southern annular mode, respectively.

High particulate carbon deposition in Lhasa—a typical city in the Himalayan–Tibetan Plateau due to local contributions

The Himalayan–Tibetan Plateau is a typical remote region with sparse air pollution. However, air pollution in cites of the inner Himalayan–Tibetan Plateau is relatively serious due to emissions from local residents. Carbonaceous aerosols are not only an important component of air pollutants that affect the health of local residents but also an important trigger of climate change. In this study, the annual wet and dry deposition rates of carbonaceous particles were investigated in Lhasa—a typical city in the Himalayan–Tibetan Plateau, by collecting precipitation and dry deposition samples and analyzing with a thermal-optical measurement protocol. The results showed that the in-situ annual wet deposition rates of water-insoluble organic carbon (WIOC) and black carbon (BC) were 169.6 and 19.4 mg m−2 yr−1, respectively, with the highest and lowest values occurring in the monsoon and non-monsoon periods, respectively. Both precipitation amounts and concentrations of WIOC and BC contributed to wet deposition rates. The dry deposition rates of WIOC and BC in Lhasa had an opposite seasonal variation to that of wet deposition, with annual average deposition rates of 2563.9 and 165.7 mg m−2 yr−1, respectively, which were much higher than those of the nearby glacier region and remote area. These values were also much higher than the results from modeling and empirical calculations, indicating that Lhasa is a high pollution point that cannot capture by models. The results in this study have significant implications for the transport of local emissions in Lhasa to the nearby remote and glacier regions.

Modelling the late Holocene and future evolution of Monacobreen, northern Spitsbergen

Abstract. Monacobreen is a 40 km long surge-type tidewater glacier in northern Spitsbergen. During 1991–1997 Monacobreen surged and advanced by about 2 km, but the front did not reach the maximum Little Ice Age (LIA) stand. Since 1997 the glacier front is retreating at a fast rate (∼125 m a−1). The questions addressed in this study are as follows: (1) Can the late Holocene behaviour of Monacobreen be understood in terms of climatic forcing?, and (2) What will be the likely evolution of this glacier for different scenarios of future climate change? Monacobreen is modelled with a minimal glacier model, including a parameterization of the calving process as well as the effect of surges. The model is driven by an equilibrium-line altitude (ELA) history derived from lake sediments of a nearby glacier catchment in combination with meteorological data from 1899 onwards. The simulated glacier length is in good agreement with the observations: the maximum LIA stand, the front position at the end of the surge, and the 2.5 km retreat after the surge (1997–2016) are well reproduced (the mean difference between observed and simulated glacier length being 6 % when scaled with the total retreat during 1900–2016). The effect of surging is limited. Directly after a surge the initiated mass balance perturbation due to a lower mean surface elevation is about -0.13mw.e.a-1, which only has a small effect on the long-term evolution of the glacier. The simulation suggests that the major growth of Monacobreen after the Holocene climatic optimum started around 1500 BCE. Monacobreen became a tidewater glacier around 500 BCE and reached a size comparable to the present state around 500 CE. For the mid-B2 scenario (IPCC, 2013), which corresponds to a ∼2ma-1 rise of the ELA, the model predicts a volume loss of 20 % to 30 % by the year 2100 (relative to the 2017 volume). For a ∼4ma-1 rise in the ELA this is 30 % to 40 %. However, much of the response to 21st century warming will still come after 2100.

Radar-Observed Characteristics of Precipitation in the Tropical High Andes of Southern Peru and Bolivia

AbstractThis study used the first detailed radar measurements of the vertical structure of precipitation obtained in the central Andes of southern Peru and Bolivia to investigate the diurnal cycle and vertical structure of precipitation and melting-layer heights in the tropical Andes. Vertically pointing 24.1-GHz Micro Rain Radars in Cusco, Peru (3350 m MSL, August 2014–February 2015), and La Paz, Bolivia (3440 m MSL, October 2015–February 2017), provided continuous 1-min profiles of reflectivity and Doppler velocity. The time–height data enabled the determination of precipitation timing, melting-layer heights, and the identification of convective and stratiform precipitation features. Rawinsonde data, hourly observations of meteorological variables, and satellite and reanalysis data provided additional insight into the characteristics of these precipitation events. The radar data revealed a diurnal cycle with frequent precipitation and higher rain rates in the afternoon and overnight. Short periods with strong convective cells occurred in several storms. Longer-duration events with stratiform precipitation structures were more common at night than in the afternoon. Backward air trajectories confirmed previous work indicating an Amazon basin origin of storm moisture. For the entire dataset, median melting-layer heights were above the altitude of nearby glacier termini approximately 17% of the time in Cusco and 30% of the time in La Paz, indicating that some precipitation was falling as rain rather than snow on nearby glacier surfaces. During the 2015–16 El Niño, almost half of storms in La Paz had melting layers above 5000 m MSL.

The MIS 3 maximum of the Torres del Paine and Última Esperanza ice lobes in Patagonia and the pacing of southern mountain glaciation

The timing, structure and termination of the last southern mountain glaciation and its forcing remains unclear. Most studies have focused on the global Last Glacial Maximum (LGM; 26.5–19 ka) time period, which is just part of the extensive time-frame within the last glacial period, including Marine Isotope Stages 3 and 4. Understanding the glacial fluctuations throughout the glacial period is a prerequisite for uncovering the cause and climate mechanism driving southern glaciation and the interhemispheric linkages of climate change. Here, we present an extensive (n = 65) cosmogenic 10Be glacier chronology derived from moraine belts marking the pre-global LGM extent of the former Patagonian Ice Sheet in southernmost South America. Our results show the mountain ice sheet reached its maximum extent at 48.0 ± 1.8 ka during the local LGM, but attained just half this extent at 21.5 ± 1.8 ka during the global LGM. This finding, supported by nearby glacier chronologies, indicates that at orbital time scales, the southern mid-latitude glaciers fluctuated out-of-phase with northern hemisphere ice sheets. At millennial time-scales, our data suggest that Patagonian and New Zealand glaciers advanced in unison with cold Antarctic stadials and reductions in Southern Ocean sea surface temperatures. This implies a southern middle latitudes-wide millennial rhythm of climate change throughout the last glacial period linked to the north Atlantic by the bipolar seesaw. We suggest that winter insolation, acting alongside other drivers such as the strength and/or position of the southern westerlies, controlled the extents of major southern mountain glaciers such as those in southernmost South America.

Una Breve Descripción de los Servicios Ecosistémicos, Hídricos y Culturales de la Cordillera Blanca y Su Entorno

Este artículo pretende ser una primera aproximación descriptiva a los servicios ecosistémicos, hídricos y culturales ofrecidos por la puna y la criósfera de la Cordillera Blanca del Perú. La Cordillera Blanca es la cadena de montañas tropicales con mayor número y extensión de glaciares del mundo. Igualmente, existen más de 800 lagunas, muchas de reciente formación a causa del retroceso glaciar y de la acelerada fusión de los glaciares cercanos. La criósfera y la puna son dos ecosistemas que destacan dentro de la Cordillera Blanca. La criósfera es el componente del sistema terrestre que contiene agua en estado sólido, y que se encuentra en regiones cubiertas por nieve o hielo. Más abajo, aparece la puna que en Perú se emplaza encima de los 3500 msnm, con un bioma principalmente de herbazal. Ambos ecosistemas tienen amplia distribución y elevada diversidad y hacen una contribución esencial a escala local, regional, nacional y continental. Además, ofrecen hábitats únicos para la biodiversidad, que proveen al ser humano una serie de servicios ecosistémicos de aprovisionamiento, regulación, culturales y esenciales o de apoyo, según la Evaluación de los Ecosistemas del Milenio (MEA), presentada en 2005. Entre estos servicios destaca por su importancia el aprovisionamiento de agua dulce para las actividades humanas.

Rapid sediment mapping and in situ geotechnical characterization in challenging aquatic areas

AbstractYakutat Bay, Southeast Alaska, is characterized by significant spatial variations in sediment type and dynamics. The northwestern side is supplied by sediments from the nearby glaciers, and is affected by longshore sediment transport processes, while the southeastern side has no direct sediment input, and is affected by human activities. In situ seabed investigations can be difficult, and expensive, due to logistical challenges in such remote locations. A portable free fall penetrometer (PFFP) was deployed 149 times along 16 transects in water depths of 2–48 m. The deceleration and pore pressure records during the probe's penetration into the seabed were used to characterize the surficial sediments. Equivalents of quasi‐static bearing capacity were determined using the deceleration‐depth signatures, and yielded strong variabilities ranging from 5 to 107 kPa at sediment depths of 10.3–41.9 cm. Correlating the PFFP results to visual field observations and literature, a regional classification scheme, and an updated sediment distribution map were derived. The pore pressure response was correlated to the different sediment types, and was used to assess the sediment's consolidation state. At the northwestern side, an increasing pore pressure trend indicated underconsolidated cohesive sediments. At the southeastern side, clayey sediments appeared to be more consolidated except of sediments of high organic content near the populated areas. The use of the pore pressure measurements represents a novel way for rapid sediment characterization using PFFP. The presented approach to create rapidly a regional sediment classification scheme offers a time‐ and cost‐effective method to derive seabed sediment maps in areas of difficult access and logistics.