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Sea Ice

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Sea Ice Definition

“Sea ice is frozen seawater. It forms, melts, and grows in the ocean” - National Snow & Ice Data Center

Sea ice is typically found on our Earth’s polar regions (Arctic and Antarctica)

Sea ice plays an important role in our Earth’s climate

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Sea Ice and MOSAiC

There are many people who hold knowledge about sea ice. Indigenous peoples who live in the Arctic have a deep connection and knowledge of the ice for over a millennia and the sea ice is a central part of their lives.

Animals and plants have uniquely adapted to polar climates using sea ice as a foundation for their way of life. Scientists, like the MOSAiC Expedition team, have used many methods to study sea ice from above, within, and below its surface. This slide shows just some of the ways scientists on the MOSAiC Expedition studied the sea ice throughout the year.

Ask what your students are observing about the ways scientists are measuring the sea ice.

Bring up themes about how many different ways they are looking at the surface of the ice, cylindrical columns to look through the ice, and below the ice.

Bring up themes that there are different kinds of ice/water features being measured (like melt ponds, those little pools of water at the ice surface.)

Bring up themes about the many different instruments (some look very simple like a stake in the ice or complicated like the Remote Operated vehicle (middle row, first picture on right-hand side)

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Question: What are some ways to describe sea ice?

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Some ways to describe sea ice

Freezing Point	The temperature point where saltwater freezes into ice. The average freezing point for saltwater is -1.8 ℃ or 28.8℉
Formation	As sea ice forms, needle-like ice crystals begin to form, bond, and grow together
Salinity	Concentration of dissolved salts in water. Arctic sea ice averages 30-34 practical salinity units (psu).
Density	The compactness of a substance. Sea ice as a range of density as liquid, solids, and gas are within sea ice.
Buoyancy	The ability to float in water, air or other fluid.
Color	Variation of colors depending on sea ice formation, brine channels, bubbles, and density.

While defining these, it is optional to have students fill out the graph in their worksheet. Below are additional pieces of information for sea ice descriptors

Freezing Point: freshwater freezes at 0℃ or 32℉. This means that the ocean water must be cooler in order to form sea ice.

Formation: As needle-like ice crystals form of the ice surface, they create frazil ice, which is the foundation to certain ice types you can find in the Arctic

Salinity: the salinity in the Arctic seawater is actually fresher than other oceans, which are usually at 32-37 psu

Density: Throughout the year and depending on the formation of sea ice, the density of sea ice can vary. Saltwater has a higher density than freshwater because salt adds more mass to freshwater.

Sea ice is buoyant and will float on the ocean surface. When sea ice melts, the freshwater and saltwater that make up sea ice will disperse into layers based on its buoyancy.

Color: MOSAiC scientists saw an array of colors while out on the ice. Typically the ice ranged from transparent, white, and blue. Sometimes the ice had a greenish color because of algae or organisms present in the ice.

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Sea Ice Growth

Sea ice formation depends on many factors such as oceans, winds and salinity.

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Let’s look at some cool sea ice the MOSAiC Team observed throughout the year!

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First Year Ice vs. Multiyear Ice

Sea ice is often characterized by its age. First year ice is new ice that forms during a season. It is typically flat.

Multiyear ice is sea ice that has been continuously growing amelting for many years. Multiyear ice can be identified with ridges

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Nilas Ice

Starts as a very thin and dark sheet of ice, they thicken over time by rafting, or slide on top of each other.

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Platelet Ice

Platelet ice occurs in low-salinity seawater beneath the sea ice shelf

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Ice sounds

When ocean and wind currents move, ice expands, shifts, and moves with it. As pieces of ice move closer and farther together, Newly formed platelet ice crashes against each other.

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Pancake Ice

Forms in rough seas, they eventually consolidate as ocean currents bump them together.

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Frost Flowers

Frost flowers occur when water vapor becomes solid (bypassing liquid phase) and deposits itself on the sea ice surface. They often can be seen on new sea ice.

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Melt Ponds

During melt season, ice and snow on the sea ice surface begin to melt. As it pools together, it creates

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Leads

Leads are large narrow cracks causing sea ice to move parallel to each other

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Ridges

When ice pressure from ocean and wind currents increase, sheets of sea ice pushed against each other. This causes sea ice to pile up on each other, creating little mountains on the sea ice.

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Sea Ice Extent

Sea ice extent is a measurement of the area of ocean where there is at least some sea ice. -National Snow and Ice Data Center

Image by NOAA Arctic Program

When sea ice accumulates together in the Arctic, it moves, grows and melts with the ocean and atmosphere. In the winter when there is no light, sea ice grows and in the summer sea ice melts. The spatial variability (difference of density of amount of sea ice) in the Arctic changes during the melt and growth seasons.

“Sea ice extent is a measurement of the area of ocean where there is at least some sea ice.

Usually, scientists define a threshold of minimum concentration to mark the ice edge; the most common cutoff is at 15 percent

Scientists use sea ice extent, sea ice minimum and maximum to more accurately measure where there is ice cover and where there is not in the Arctic.” (National Snow and Ice Data Center)

Sea ice extent is important to all of us because sea ice helps keep our planet cool (takes us to the ice-albedo feedback loop)

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Albedo Effect

Albedo is the solar reflectivity of a surface.

Lighter surfaces like ice reflect the sun’s energy bouncing it back to space

Darker surfaces absorb more of the sun’s energy

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Question: Who depends on sea ice?

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Why are brine channels important?

Many microorganisms and plants depend on sea ice.

Some live in the ice in brine channels, pockets of saltwater in the sea ice.

Others live below the ocean on the ice surface

Illustration of microorganisms living in brine channels

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Why are brine channels important?

Animals from plankton to polar bears depend on sea ice. Sea ice is the foundation to the Arctic food web.

These animals include: crustaceans, whales, porpoises, narwhals, polar bears, seals, fish, sea birds, sharks, and many more.

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Why are brine channels important?

Locally: Indigenous and local communities in the Arctic depend on healthy sea ice to sustain their way of life.

Sea ice is used as a way of transport, to travel from one place to another

People harvest the lands and ice (hunting)

Globally: regulates our climate system

Image from PMEL Arctic Zone

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Understanding Sea Ice

With science-based reasoning, understanding the attributes of sea ice allows us to monitor sea ice throughout the years

Scientists use instruments to measure changes in sea ice on different spatial (distance) and temporal (time) scales

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LAB WORK!

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Ice Cores in the Field

Scientists on MOSAiC collected hundreds if not thousands of ice cores in the field to understand the properties of sea ice and how they connect to the Arctic climate and ecosystem.

In the field immediately after coring they would measure, describe attributes, drill for temperature, then slice them for scientists to analyze in their labs.

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Brine Channels, Biology, and the Atmosphere

Take a look at MOSAiC atmospheric scientist Jessie Creamean who studies the relationships between marine animals and the atmosphere. Here is her summary of her talk you will watch an excerpt of.

“Join Jessie Creamean from Colorado State University, fresh off leg one of the MOSAiC Arctic Expedition as they share their incredible Arctic Journey! How do you collect samples over a year of being trapped in the Arctic ice? What is the MOSAiC team sampling? Once you have a sample of ice or air or phytoplankton, how do you store it and then transport it? Sara and Jessie are part of the science team and will have answers to all these questions and much more! We'll also dive in with the animals Jessie was able to see from the ship to highlight a little Arctic BackyardBio!” - Exploring by the Seat of Your Pants

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End