scholarly journals Late Pleistocene and early Holocene sea-level history and glacial retreat interpreted from shell-bearing marine deposits of southeastern Alaska, USA

Geosphere ◽  
2021 ◽  
Author(s):  
James F. Baichtal ◽  
Alia J. Lesnek ◽  
Risa J. Carlson ◽  
Nicholas S. Schmuck ◽  
Jane L. Smith ◽  
...  
Keyword(s):  
Sea Level ◽  
Early Holocene ◽  
Paleoenvironmental Reconstruction ◽  
Site Location ◽  
Data Set ◽  
Study Region ◽  
Level Curves ◽  
Ice Caps ◽  
Marine Deposits ◽  
Air Temperatures

We leverage a data set of >720 shell-bearing marine deposits throughout southeastern Alaska (USA) to develop updated relative sea-level curves that span the past ~14,000 yr. This data set includes site location, elevation, description when available, and 436 14C ages, 45 of which are published here for the first time. Our sea-level curves suggest a peripheral forebulge developed west of the retreating Cordilleran Ice Sheet (CIS) margin between ca. 17,000 and 10,800 calibrated yr B.P. By 14,870 ± 630 to 12,820 ± 340 cal. yr B.P., CIS margins had retreated from all of southeastern Alaska’s fjords, channels, and passages. At this time, isolated or stranded ice caps existed on the islands, with alpine or tidewater glaciers in many valleys. Paleoshorelines up to 25 m above sea level mark the maximum elevation of transgression in the southern portion of the study region, which was achieved by 11,000 ± 390 to 10,500 ± 420 cal. yr B.P. The presence of Pacific sardine (Sardinops sagax) and the abundance of charcoal in sediments that date between 11,000 ± 390 and 7630 ± 90 cal. yr B.P. suggest that both ocean and air temperatures in southeastern Alaska were relatively warm in the early Holocene. The sea-level and paleoenvironmental reconstruction presented here can inform future investigations into the glacial, volcanic, and archaeological history of southeastern Alaska.

Late Quaternary glacial and sea-level events, Clements Markham Inlet, northern Ellesmere Island, Arctic Canada

1986 ◽  
Vol 23 (9) ◽  
pp. 1343-1355 ◽  
Author(s):  
Jan Bednarski
Keyword(s):  
Sea Level ◽  
Late Quaternary ◽  
Ellesmere Island ◽  
Glacial Retreat ◽  
Radiocarbon Dates ◽  
Ice Caps ◽  
Marine Deposits ◽  
Ice Retreat ◽  
Level Ice ◽  
Small Valley

Clements Markham Inlet cuts into the Grant Land Mountains of the northernmost coast of Ellesmere Island. The head of the inlet is bounded on three sides by mountain ice caps that surround lowlands mantled by extensive raised marine deposits. Fieldwork and mapping of late Quaternary sediments were used to determine the limits of past glaciations and the nature of ice retreat from the inlet head. Forty-five radiocarbon dates on driftwood and marine shells provide a deglacial chronology and document related sea-level adjustments.High-level ice-marginal meltwater channels and mountain summit erratics indicate that ice once inundated all of Clements Markham Inlet. During at least one of these undated glaciations, ice flowed unconstrained by the local topography. In contrast, the most recent glaciation involved confluent trunk glaciers, which terminated near the head of the inlet. Beyond this terminus, smaller glaciers entering the sides of the inlet debouched into a glacioisostatically depressed sea (full glacial sea). Retreat from the last glaciation is documented by moraines, kame terraces, and ice-contact deltas.Inside the ice limit at the head of the inlet, sections commonly show that a marine transgression occurred immediately after the retreat of the ice. Conversely, sections outside the last ice limit, along the sides of the inlet, show complex intercalations of marine and glacigenic sediments. These indicate proximal ice-front conditions where small valley glaciers locally contacted the sea.The oldest date on the last ice limit is 9845 BP. After this, slow retreat was in progress, and some glaciers were within 6 km of their current positions by ca. 9700 BP. At the head of the inlet, the mouths of the confluent valleys became ice free by 8000 BP. After 8000 BP, glacial retreat accelerated greatly, so that the entire lowland became ice free within 400 years.Relative sea-level curves from the inlet indicate ice-load changes that confirm this pattern of ice retreat. Outside the last ice limit, the full glacial sea reached 124 m asl by at least 10 000 BP. Emergence from this sea occurred slowly between at least 10 000 and 8000 BP (0.72 m 100 year−1). This period was followed by "normal" rapid postglacial emergence, which decelerated to the present.The marine limit of the full glacial sea rises from 92 m asl, at the outer coast, to 124 m asl near the last ice limit at the head of the inlet. Initial emergence from the full glacial sea occurred simultaneously throughout the inlet. On the proximal side of the last ice limit, the marine limit descends in the up-ice direction and becomes progressively younger. Individual strandlines tilt up in a southwesterly direction towards the central Grant Land Mountains, suggesting a former centre of glacio-isostatic loading in that area.

scholarly journals A high-resolution bedrock map for the Antarctic Peninsula

2014 ◽  
Vol 8 (4) ◽  
pp. 1261-1273 ◽  
Author(s):  
M. Huss ◽  
D. Farinotti
Keyword(s):  
High Resolution ◽  
Sea Level ◽  
Antarctic Peninsula ◽  
Dynamic Modelling ◽  
Ice Thickness ◽  
Data Set ◽  
Ice Flow ◽  
Study Region ◽  
Entire Study ◽  
The Antarctic

Abstract. Assessing and projecting the dynamic response of glaciers on the Antarctic Peninsula to changed atmospheric and oceanic forcing requires high-resolution ice thickness data as an essential geometric constraint for ice flow models. Here, we derive a complete bedrock data set for the Antarctic Peninsula north of 70° S on a 100 m grid. We calculate distributed ice thickness based on surface topography and simple ice dynamic modelling. Our approach is constrained with all available thickness measurements from Operation IceBridge and gridded ice flow speeds for the entire study region. The new data set resolves the rugged subglacial topography in great detail, indicates deeply incised troughs, and shows that 34% of the ice volume is grounded below sea level. The Antarctic Peninsula has the potential to raise global sea level by 69 ± 5 mm. In comparison to Bedmap2, covering all Antarctica on a 1 km grid, a significantly higher mean ice thickness (+48%) is found.

scholarly journals Early Holocene sea-level changes in Øresund, southern Scandinavia

1969 ◽  
Vol 26 ◽  
pp. 29-32
Author(s):  
Ole Bennike ◽  
Martin Skov Andreasen ◽  
Jørn Bo Jensen ◽  
Matthias Moros ◽  
Nanna Noe-Nygaard
Keyword(s):  
Sea Level ◽  
Sediment Cores ◽  
Early Holocene ◽  
Sea Level Changes ◽  
Relative Sea Level ◽  
Data Set ◽  
The North ◽  
Global Sea Level ◽  
The Baltic ◽  
Water Depths

The Baltic Sea and Kattegat are connected via three straits: Storebælt, Lillebælt and Øresund (Fig. 1). Øresund is the shallowest with a threshold around 7 m deep and increasing water depths to the north (Fig. 2). In the early Holocene, global sea-level rise led to reflooding of Øresund. It started in northern Øresund which was transformed into a fjord. However, so far the timing of the transgression has not been well determined, but sediment cores collected north of the threshold, at water depths of 12 to 20 m, and a new series of radiocarbon ages help to constrain this. As the relative sea level continued to rise, the threshold in Øresund was also flooded, and Øresund became a strait. In mid-Holocene time, the relative sea level rose until it was 4–5 m higher than at present, and low-lying areas around Øresund became small fjords. During the late Holocene, the relative sea level fell again. Part of the data set discussed here was presented by Andreasen (2005).

scholarly journals A high-resolution bedrock map for the Antarctic Peninsula

2014 ◽  
Vol 8 (1) ◽  
pp. 1191-1225
Author(s):  
M. Huss ◽  
D. Farinotti
Keyword(s):  
High Resolution ◽  
Sea Level ◽  
Antarctic Peninsula ◽  
Dynamic Modelling ◽  
Ice Thickness ◽  
Data Set ◽  
Ice Flow ◽  
Study Region ◽  
Entire Study ◽  
The Antarctic

Abstract. Assessing and projecting the dynamic response of glaciers on the Antarctic Peninsula to changed atmospheric and oceanic forcing requires high-resolution ice thickness data as an essential geometric constraint for ice flow models. Here, we derive a complete bedrock data set for the Antarctic Peninsula north of 70° S on a 100 m grid. We calculate distributed ice thickness based on surface topography and simple ice dynamic modelling. Our approach is constrained with all available thickness measurements from Operation IceBridge and gridded ice flow speeds for the entire study region. The new data set resolves the rugged subglacial topography in great detail, indicates deeply incised troughs, and shows that 34% of the ice volume is grounded below sea level. The Antarctic Peninsula has the potential to raise global sea level by 71 ± 5 mm. In comparison to Bedmap2, covering all Antarctica on a 1 km grid, a significantly higher mean ice thickness (+48%) is found.

Ecostratigraphical interpretation of lower Middle Ordovician East Baltic sections based on brachiopods

2009 ◽  
Vol 146 (5) ◽  
pp. 717-731 ◽  
Author(s):  
CHRISTIAN M. Ø. RASMUSSEN ◽  
ARNE T. NIELSEN ◽  
DAVID A. T. HARPER
Keyword(s):  
Shallow Water ◽  
Sea Level ◽  
Fourth Order ◽  
Water Depth ◽  
Soft Substrate ◽  
Middle Ordovician ◽  
Systematic Assessment ◽  
Level Curves ◽  
Ice Caps ◽  
Baltic Area

AbstractA detailed ecostratigraphical framework is established for the lower Middle Ordovician Kundan regional stage of the East Baltic area corresponding to the Asaphus expansus, A. raniceps and A. eichwaldi trilobite zones (lower Darriwilian). The study is based on approximately 6200 brachiopods collected bed by bed from limestone sections in northern Estonia (Harku Trench and Saka) and western Russia (Putilovo Quarry, Lava River canyon and Lynna River valley) with, in addition, the first detailed systematic assessment of the Kundan brachiopods of the East Baltic. These sections represent an oblique depth transect some 400 kilometres long, deepening eastwards. Five biofacies associations have been recognized using detrended correspondence and cluster analyses: a shallow-water Lycophoria association, a transitional Gonambonites association and two deeper-water associations, the soft-substrate Orthis callactis and the hard-substrate Orthambonites associations. A separate, fifth soft-substrate association is present in the marl beds at the main locality of Putilovo Quarry. The associations reflect a combination of palaeo-water depth and substrate. The biofacies facilitate an ecostratigraphical correlation along the transect, and third and fourth order sea-level curves are reconstructed, reflecting mainly eustasy. The sea-level was relatively low, early in the Kundan, but then rose significantly into the A. raniceps Biozone. This corroborates the recent discovery of possible small early Darriwilian ice caps on Gondwana.

Increased winter warm events in Iceland drive enhanced glacier velocity and melting

2021 ◽  
Author(s):  
Jane Hart ◽  
Kirk Martinez ◽  
Nathaniel Baurley ◽  
Benjamin Robson
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Water Pressure ◽  
Surface Velocity ◽  
Unconsolidated Sediments ◽  
Glacier Surface ◽  
Data Set ◽  
West Antarctic ◽  
Air Temperatures ◽  
Glacier Velocity

<p>A key element in the comprehension of the response of glaciers to climate change is an understanding of the bed conditions, and these are a vital component of ice sheet models. The West Antarctic ice streams are potentially highly unstable, with implications for rapid sea level rise. These are underlain by unconsolidated sediments (soft-bed), which have a distinct but rarely studied subglacial hydrology. We present a detailed data set from Skálafellsjökull, a soft-bedded glacier in Iceland, as an analogue for other soft-bedded glaciers. These data include wireless in situ till water pressure, meteorological, surface melt, discharge and glacier surface velocity from GPS as well as remote sensing imagery. We show how short-term warm events during winter can effect annual velocity, and how the number of warm events has increased over the last 10 years. We argue this was because water was stored in a soft-bed subglacial reservoir where it could be rapidly released during winter, with the resultant storage levels effecting the following summer dynamics.  To test whether warm winter events are unique to Iceland, we analyzed the daily air temperatures record of 18 World Glacier Monitoring Service ‘reference’ glaciers (1979-2018). We were able to show that periods of warm temperatures during winter were present in maritime locations, and the number of these events had increased in locations where winter temperatures had also increased. We propose that winter events are an important component of glacier retreat and sea level rise that have hitherto not been examined in detail.</p>

Could climate engineering save the Greenland Ice Sheet?

2016 ◽  
Author(s):  
Patrick J. Applegate ◽  
K. Keller
Keyword(s):  
Sea Level Rise ◽  
Greenhouse Gas Emissions ◽  
Greenhouse Gas ◽  
Sea Level ◽  
Computer Model ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Upper Atmosphere ◽  
Climate Engineering ◽  
Air Temperatures

Engineering the climate through albedo modification (AM) could slow, but probably would not stop, melting of the Greenland Ice Sheet. Albedo modification is a technology that could reduce surface air temperatures through putting reflective particles into the upper atmosphere. AM has never been tested, but it might reduce surface air temperatures faster and more cheaply than reducing greenhouse gas emissions. Some scientists claim that AM would also prevent or reverse sea-level rise. But, are these claims true? The Greenland Ice Sheet will melt faster at higher temperatures, adding to sea-level rise. However, it's not clear that reducing temperatures through AM will stop or reverse sea-level rise due to Greenland Ice Sheet melting. We used a computer model of the Greenland Ice Sheet to examine its contributions to future sea level rise, with and without AM. Our results show that AM would probably reduce the rate of sea-level rise from the Greenland Ice Sheet. However, sea-level rise would likely continue even with AM, and the ice sheet would not regrow quickly. Albedo modification might buy time to prepare for sea-level rise, but problems could arise if policymakers assume that AM will stop sea-level rise completely.

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