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Paleoceanography

This category contains 21 posts
A Greenland ice core segment, extracted from the ice sheet. Ice cores trap past climate conditions, allowing researchers to study paleoclimates. Credit: wikicommons.

The Bipolar See-Saw: Dansgaard-Oeschger Events and the Antarctic Climate

Within large timescales of glacial and interglacial periods, mini, rapid climate shifts may occur thanks to oceanic circulation processes and balancing global ocean budgets. The events in question originate in the North Atlantic; but, how do they affect the Antarctic?

photo credit: Anne Hartwell

Glaciers have big league role in silica budget.

Glaciers get a lot of attention because they’re expansive sheets of ice. They’re important to understand because they can impact sea level, circulation, climate, albedo, and they are homes to microbial organisms and large animals. A new reason they are getting attention is their recently realized importance to the global silica budget. Researchers found that melting glaciers deliver enough silica to the surface ocean that their contribution should not be ignored.

Figure 2: Kavachi Eruption: Image courtesy of Submarine Ring of Fire 2002: Explorer Ridge. https://upload.wikimedia.org/wikipedia/commons/0/0a/May_14_Kavachi_eruption.jpg

Sharkcano, a melting pot for biology

No, a Sharkcano is not a volcano that erupts sharks. IT IS WAY COOLER THAN THAT! It is a submarine volcano that hosts a diverse macro community in water that is much warmer and more acidic that the surrounding seawater. Read more to find out about this alien-esc ecosystem in the South Pacific Ocean.

Figure 1(a): Plate tectonic reconstruction of the Tethys realm at 249 Ma. A rift forms off the north coast of South Pangea (Gondwana) and piece of continental shelf (Cimmera) moves north, pushing up the Paleo-Tethys ocean and creating the Neo-Tethys. (b) Plate tectonic reconstruction of the Tethys realm at 100 Ma. The Neo-Tethys is present where the Paleo-Tethys once was, and Gondwana has started to break apart into recognizable continents.

Mediterranean Magnetism shows Ancient Oceanic Crust

Compared to the continents, oceanic crust is relatively young, less than 200 million years. But in a corner of the Mediterranean Sea, a remnant of the ancient Neo-Tethys Ocean lurks from the time of Pangaea.

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Can bumps in the seafloor explain glacial-interglacial cycles?

The best scientific theories bring lots of things together in unexpected ways. This one has ice ages, seafloor volcanoes, sea level changes, wobbles in the earth’s rotation, and much more!

This artist’s impression shows how Mars may have looked about four billion years ago. The young planet Mars would have had enough water to cover its entire surface in a liquid layer about 140 metres deep, but it is more likely that the liquid would have pooled to form an ocean occupying almost half of Mars’s northern hemisphere, and in some regions reaching depths greater than 1.6 kilometres. (M. Kornmesser via Wikipedia)

Paleo-oceanography from satellite data reveal ancient tsunamis…on Mars?!

Extraplanetary tsunamis. Need I say more?

Figure 2. Scanning electron microscope images of left: Fragilariopsis kerguelensis. This diatom species lives in the open ocean waters of the Antarctic Circumpolar Current. (Photo by F. Hinz, http://www.awi.de/en/news/background/species_of_the_month/august/) Right: Fursenkoina fursiformis. This foraminifera species is found at the seafloor beneath waters where there is high primary productivity and export of organic carbon. (www.foraminifera.eu)

Tiny shells tell the history of Antarctic ice

Over the past 10,000 years, the West Antarctic Ice Sheet has gone through long periods of growth and long periods of retreat. Shells from the tiny organisms living in the seawater throughout the millennia can be used to reconstruct the history of times when warmer water from offshore came onto the shelf and weakened the ice shelf and what that means for the future.

Chesapeake Bay. Credit: NASA Landsat.

The Down, Up, and Down Again of Chesapeake Bay

The Chesapeake Bay region is a densely populated area, and also experiences more rapid sea level rise than anywhere else along the North American Atlantic Coast. Why? Scientists look to the lithosphere for answers, finding that the subsidence of an ancient lithospheric bulge may be partially to blame, and will continue for millennia.

Figure 2: Drawing of early European farmers applying a slash and burn practice to make croplands.

CSI Holocene: Who started the fire?

Sediment and ice cores suggest that peaks in fire activity that happened 2,500 years ago in Europe was likely caused by early humans applying the slash and burn technique to clear away forests. This demonstrates that the anthropogenic carbon footprint dates back further than the Industrial Revolution.

Changes in Temperature and CO2 over the past 422,000 years. Data obtained from Vostok ice cores in Antarctica. Credit: NOAA.

Balancing Act: Marine Sediments Reveal Past Carbon Cycle Fluxes

Researchers conducted a study that looks at marine sediment records to investigate sediment weathering patterns over long-term climate cycles. Somewhat surprisingly, it appears the Earth may have a mechanism for balancing variations in weathering during these glacial-interglacial cycles and mediating carbon cycle fluxes.

Source: Monterey Bay National Marine Sanctuary

Path of Corrosion: How Scientists Modeled Ancient Sea-Floor Acidity

Today, we see a rapid release of CO2 to the atmosphere associated with climate change. The same was true 55 million years ago during the PETM, a time when – sediment records show – there was pervasive carbonate dissolution along the sea floor. But it was not the same pattern everywhere. Scientists attempt to model these spatial varieties and explain what occurred.

http://walkingwith.wikia.com/wiki/Precambrian_Era

A 2.5 billion year old story about iron in the ocean, told by a rock

New light has been shed on the possibility of an alternative iron sink than previous thought prior to the oxygenation of the oceans 2.45 billion years ago. The findings could affect our interpretations of the early seawater chemistry, nutrient cycling, and trace metal distribution in the Precambrian.

BEM 2015

Best of Benthics

The Top 5: Highlights and notes from an eventful Benthic Ecology Meeting!

Figure 1.  Mean annual modern-day sea surface temperature reconstruction.  Sediment core site locations labeled.  Centered on ODP 806, the western equatorial warm pool contains some of the warmest surface waters on Earth.  The eastern equatorial Pacific, often referred to as the cold tongue, is the narrow band of regionally cool surface waters centered on ODP 850.  The gradient between the warm pool and the cold tongue has major implications for global climate.

Just How Permanent was El Niño in the Past?

New data refutes the hypothesis that permanent El Niño conditions existed in the tropical Pacific more than 3 million years before present, favoring climate variability more similar to modern-day.

Argentina_AMO_2010024_lrg

Ironing Out the Details of the Last Ice Age

“Give me a half tanker of iron and I will give you an ice age!”, as was once said by Dr. John Martin, simplistically describes the iron hypothesis. This concept suggests that additions of iron to the ocean can ramp up biological productivity and account for some of the decreasing atmospheric carbon dioxide concentrations during the last ice age.

Fig 2. Locations of core sites.

Rapid Reductions in North Atlantic Deep Water during the Peak of the Last Interglacial Period

North Atlantic deep water forms primarily in more extreme northern latitudes due to the colder, saltier water with a higher density. When this flow of water goes south it mixes with the cold Antarctic water and then redistributes into other parts of the world. As high latitude warming and ocean refreshing reduce water density, North Atlantic Deep Water (NADW) formation can be prohibited.

Figure 3.  Conceptual model showing a northern to southern hemisphere transect at three time instances: Pliocene (>3.3 Ma), Pleistocene transition (2.7 - 2.5 Ma) and Modern (2 - 0 Ma).

Hello Glaciers, Goodbye Winds!

With the intensification of glaciation in the northern hemisphere approximately 2.7 million years ago, the prominent westerly wind belts responded by shifting towards the equator based on evidence from sediment cores. But how exactly are scientists able to determine the position of the winds millions of years ago? The answer lies in proxies!

Figure 1: Present day vegetation map of the study area. Colors indicate the modern day % of grasses were the darker green represents the lowest abundance of C4 grasses. The red dot (MD03-2607) is the location of the sediment core used in this study. The blue lines represent the River Murray. Black lines are summer/winter rainfall boundaries.

We didn’t start the fire!… that changed the southeast Australian landscape 44 thousand years ago

A sediment core suggests that the large ecosystem changes that occurred in southeastern Australia were caused by the extinction of large grazers, not human-controlled fire use, which caused fire-prone forest vegetation to overtake the grassy landscape.

Adriatic

Reconstructing climate history from sediments in the Gulf of Taranto, Italy

What was the climate like in Southern Italy 10,000 years ago? This question and many more can be answered by collecting sediment from the seafloor. Understanding the types of sediment and where it all came from, and determining the age of deposition make it possible to reconstruct the history of regional climate.

Pohl_Dec_OB

Why lions can thank wildfires for the African Savanna

Sediment records show that wildfires caused the initial expansion of grasslands in Africa during the Miocene (8 million years ago) allowing the African Savanna to evolve into the spectacular ecosystem we know today.

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