Baffin Bay near Greenland and sea floor features indicative of a large ice shelf in the past.
About 20,000 years ago, when a literal reading of biblical chronology would have us believe that Earth had yet to be created, an enormous floating ice shelf occupied Baffin Bay between Greenland and Canada. Its existence is recorded in physical evidence: the marks it left on the seabed and the sediments that help reconstruct its disappearance. Together, these preserve a history of an Ice Age landscape undergoing profound change, thousands of years before the supposed creation of the world.
The discovery, described in a paper in Nature Geoscience by Shannon A. Klotsko and colleagues, indicates that this ice shelf covered approximately 150,000 square kilometres and was around 1.4–2.1 kilometres thick. Comparable in area to major ice shelves in modern Antarctica, it helped buttress three neighbouring ice sheets: the Laurentide, Innuitian and Greenland ice sheets. This floating mass acted as a restraint on the movement of land-based ice towards the sea.
The researchers identified seafloor features that reveal the former ice shelf’s remarkable extent and thickness. Mapping showed evidence of ice contact deep along the continental slope. The team interpreted these features as the imprint of a vast, basin-spanning ice shelf, whose dimensions could be reconstructed with allowance for past relative sea level.
Sediment cores provide another part of the story. The researchers suggest that the shelf disappeared over approximately 500–1,000 years, although the precise timing remains uncertain. The researchers infer that losing this restraint helped trigger rapid retreat of the surrounding ice sheets. This is a reconstruction from geological evidence, with uncertainties explicitly recognised, rather than a claim that every stage of the process is known.
For young-Earth creationism, the difficulty is considerably greater than explaining away a few layers of mud. Floods can deposit layers, so layering by itself is not the decisive point. What requires explanation is the combination of an ancient glacial setting, ice-contact landforms, sedimentary evidence and a sequence of environmental changes. A single recent global inundation provides no adequate account of that history. Nor does invoking a catastrophe that supposedly remodelled Earth’s surface explain the preservation of evidence from a much older glacial world.
Here, then, is another example of scientists reading Earth’s history from evidence that can be examined and tested. They did not begin with a requirement that Baffin Bay must once have contained an enormous ice shelf; the evidence led them to that conclusion. The result adds detail to our understanding of the last ice age and offers a potentially important comparison with Antarctica today. For biblical literalism, meanwhile, it adds another substantial chapter to a planetary history that supposedly never happened.
How the Seabed Preserves the History of an Ice Age. The seabed is both a landscape shaped by past events and an archive of sediments deposited afterwards. By studying these together, scientists can reconstruct the former extent of ice, changes in marine conditions and the sequence of glacial retreat. The following are general methods used in marine geology; not every technique is necessarily employed in an individual study.Unusually, we have two different news items from two of the Universities involved in this release - a report from the University of North Carolina Wilmington, and another from the University of Florida:
- Ice leaves marks on the seabed
Where moving ice contacts the sea floor, it can scrape grooves, mould sediment into streamlined features and push material into ridges. Sonar surveys map these landforms, allowing researchers to examine their depth, orientation and geographical relationships. Their shapes and distribution help distinguish the effects of ice from those of currents, submarine landslides and other processes.
In Baffin Bay, researchers traced deep ice-contact features around much of the continental slope. They interpret these as evidence of a vast floating ice shelf whose underside contacted the sloping seabed. Reconstructing its thickness requires allowance for past relative sea level, which was affected by both ocean volume and changes in the height of the land under the weight of ice.
- Sediment cores preserve a sequence of changing conditions
A sediment core is a column of material extracted from beneath the seabed. Where the sequence has not been overturned or disturbed, deeper deposits are generally older than those above them. Changes in grain size, mineral composition, fossil content and sediment structure provide clues to the conditions under which successive deposits accumulated.
For example, icebergs can carry stones and sand out to sea and release them as they melt. This ice-rafted debris may become embedded in much finer seabed sediment. Its abundance and composition can help reveal changes in the delivery and source of floating ice. However, it is not a simple measure of temperature: iceberg routes, melting, currents and the position of the ice margin also matter.
Tiny marine fossils provide additional evidence. Different organisms favour different environmental conditions, so changes in their assemblages can help reconstruct changes in the sea. A core is therefore more informative than a stack of visible layers: it contains several kinds of evidence that can be compared.
- Dates turn a sequence into a chronology
The order of deposits establishes which events came first, but their ages require further evidence. For sediments from the last several tens of thousands of years, radiocarbon dating of suitable preserved material, including marine shells, is an important method. Researchers use dates from different depths to construct an age–depth model, estimating how the age of the sediment changes down the core.
Marine radiocarbon dates require particular care. Ocean water can contain carbon that is already depleted in radiocarbon before an organism incorporates it into its shell. This marine reservoir effect can make the shell appear older than a contemporary terrestrial sample. Calibration and appropriate reservoir corrections are therefore essential, and uncertainties must be included in the resulting chronology.
Researchers must also check for older material that has been eroded and redeposited, mixing by burrowing organisms, and gaps caused by erosion or non-deposition. They do not assume that every visible layer represents one year or that sediment accumulated at a constant rate.
- Independent clues constrain the reconstruction
Seafloor landforms show where ice made contact with the bed. Sediment properties reveal changing depositional conditions. Fossils and dating evidence add environmental and chronological constraints. Agreement between different cores and different kinds of evidence strengthens a reconstruction; disagreement identifies questions that require further investigation.
For Baffin Bay, the researchers combine mapped landforms with evidence from sediment cores to infer the existence and subsequent loss of a large ice shelf. The suggestion that its collapse helped trigger retreat of the surrounding ice sheets is a geological interpretation, and the precise timing remains uncertain. Recognising those limits is part of evaluating the evidence.
- Why “a flood made the layers” is not an explanation
Floods can produce layered deposits, and rapid deposition does occur in the oceans. Layering alone therefore establishes neither great age nor the absence of flooding. The scientific question is whether a proposed explanation accounts for the whole record: sediment contents and structures, fossil assemblages, dates, erosion surfaces and associated landforms.
A single recent global flood does not explain away evidence of an ancient ice shelf, its interaction with the seabed and the subsequent changes recorded in marine sediments. Any alternative must explain those observations and their chronological relationships. Calling them “Flood deposits” supplies a label, not a mechanism or a demonstrated history.
New Discovery Sheds Light on Ancient Baffin Bay Ice Shelf
Associate Professor Shannon Klotsko, Department of Earth and Ocean Sciences, is the lead author of a recent paper published in Nature Geoscience, focusing on her team’s discovery of a new feature on the seafloor that points to an ancient ice shelf that existed in Baffin Bay during the last ice age.
See the Article in Nature Geoscience: The Baffin Bay Ice Shelf stabilized three adjacent ice sheets during the last glacial period Baffin Bay, located between Greenland and Canada, was once home to an expansive ice shelf that researchers estimate covered approximately 150,000 square kilometers. The Baffin Bay Ice Shelf was between 1,400 and 2,100 meters thick, making it thicker than modern Antarctic ice shelves.
Researchers compiled seafloor bathymetric data and studied features along the Baffin Bay continental slope to determine the extent and maximum depth of the ancient ice shelf. Their findings indicate the ice shelf helped stabilize and promote the thickening of the Laurentide, Innuitian and Greenland ice sheets, which came together in Baffin Bay during the last ice age.
We didn’t set out to find an ice shelf this thick when we embarked on the research cruise for our project, the Baffin Bay Deglacial Experiment, so finding these imprints of ice on the seafloor at such great depths was a huge surprise.
Associate Professor Shannon A. Klotsko, first author.
Department of Earth and Ocean Sciences, and Center for Marine Science
University of North Carolina Wilmington
Wilmington, NC, USA.
The team also found evidence that the collapse of the Baffin Bay Ice Shelf triggered rapid retreat of the surrounding ice sheets. The findings show how the loss of an ice shelf can quickly reorganize marine ice sheets and may offer a comparison for how weakening ice shelves could affect future ice sheet retreat in Antarctica.Modern ice shelves help prevent Antarctic ice sheets from rapidly draining into the ocean, which would cause significant global sea level rise, so finding one of a similar size in the past that disappeared in 500–1,000 years is a bit scary when thinking about the future of our coasts.
Associate Professor Shannon A. Klotsko.
From Florida University:
How a massive ice shelf buttressed the last ice age’s glaciers — and what it could mean for Antarctica today
- A massive Baffin Bay ice shelf once buttressed three major ice sheets across Greenland and northern Canada.
- The ice shelf disappeared over hundreds to thousands of years, followed by accelerated retreat of the glaciers it had helped restrain.
- Examples of past large ice shelves like this provide an opportunity to study the mechanisms that can destabilize ice sheets, relevant to the study of Antarctica today.
About 20,000 years ago, an enormous, floating ice shelf more than a mile thick helped lock in three of the largest ice sheets in northern Canada and Greenland. When that ice shelf disappeared, it helped unlock part of these ice sheets, which contributed to hundreds of feet of sea level rise, establishing modern coastlines as we know them.
Those are the findings of a new study that uncovered evidence of an ancient ice shelf in Baffin Bay, west of Greenland. The size and scale of such a floating fortress of ice was not previously known, and it provides clues to the future of today’s massive ice sheets in Antarctica and the sea-level rise that could follow if they melt.
These ice sheets are like a gothic cathedral. You have this big, tall cathedral of ice and these flying buttresses of floating ice shelves that support them. They help stop the ice on land from flowing into the ocean and contributing to sea level rise. One of the biggest concerns in Antarctica right now is how fast will that ice that’s on land flow into the ocean when we lose that buttressing effect.
Associate Professor Robert Hatfield, Ph.D., co-author
Department of Geological Sciences
University of Florida
Gainesville, FL, USA.
Hatfield and his collaborators at the University of North Carolina Wilmington, Columbia University and four other institutions published their findings Oct. 21 in Nature Geoscience.
The scientists did not set out to discover a mile-thick ice shelf. Instead, they embarked on a five-week-long research cruise in Baffin Bay intent on collecting sediment cores to reconstruct what destabilized the Greenland Ice Sheet at the end of the last ice age.
Yet with sonar mapping the seafloor, they uncovered clear evidence of a large ice shelf occupying the entire bay and holding back not only the margin of the Greenland Ice Sheet to the east but the Innuitian Ice Sheet to the north and the Laurentide Ice Sheet to the west.
The thing that really surprised us was this evidence was over a mile deep into the ocean. That’s at least half a mile thicker than any previously known ice shelf in the Northern Hemisphere. Ice doesn’t want to flow down underwater, it wants to be afloat. It just speaks to how thick that ice shelf became.
Associate Professor Robert Hatfield, Ph.D.
Sediment cores from across the bay suggest that this floating ice shelf — which was roughly the size of some of the key ice shelves in Antarctica today — disappeared over about 500-1000 years, allowing the large glaciers on land to flow faster into the sea, melt and raise the ocean levels.
That’s one of the scary takeaways we didn’t expect, that an ice shelf the scale of the ones in Antarctica could completely disappear in a matter of centuries.
Associate Professor Robert Hatfield, Ph.D.
With these new findings in hand about the end of the last ice age, scientists who model past and present ice shelves and glaciers have new data to work with, Hatfield said. That could lead to more accurate predictions about how quickly Antarctic glaciers might melt and raise sea levels.
And the study reveals how following unexpected evidence can reveal entirely new pictures of the planet’s past.We didn’t go out to look for an ice shelf this big. That’s science, right? You go out to look for one thing and all sorts of other questions fall into your lap.
Associate Professor Robert Hatfield, Ph.D.
Publication:
The Baffin Bay discovery adds another substantial piece to a history that young-Earth creationism cannot accommodate. Here was an enormous ice shelf restraining three neighbouring ice sheets, leaving its imprint on the seabed and subsequently disappearing as the glacial world changed. The wider sedimentary record, summarised in the earlier research, preserves thousands of years of environmental change entirely before the date assigned to Creation in the familiar Ussher chronology. This is a detailed physical history of a world that, according to that chronology, did not yet exist.
Invoking Noah’s Flood does nothing to resolve the difficulty. Floodwater can deposit sediment in layers, but that observation does not explain the ages, contents and relationships of these deposits, or the glacial landforms alongside them. A proposed global catastrophe must account for the evidence as a whole, including the preservation of a much older landscape and its sedimentary history. Simply calling everything a product of the Flood leaves the actual geological questions unanswered.
The research also illustrates how scientific understanding develops. Researchers combine new seabed surveys with sediment records, test interpretations and acknowledge uncertainty about the timing and consequences of ice-shelf collapse. Further evidence may refine that reconstruction. Such revisions are a strength of a method that allows observations to change conclusions; they provide no justification for replacing the evidence with a predetermined biblical narrative.
Understanding this ancient ice shelf also has practical value. Its apparent role in stabilising surrounding ice sheets offers a comparison with Antarctica and the consequences of losing similar restraints today. Reading Earth’s history accurately helps us investigate its future. Insisting that the history never happened contributes nothing to either task.
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