Processes that took place through Earth's history, such as the weathering of rocks, evaporation of ocean water, and the formation of sea ice, have made the ocean salty. Those are still at work today and are counterbalanced by processes that decrease the salt in the ocean, like freshwater input from rivers, precipitation, and the melting of ice. The result is an ocean surface where the salinity - the concentration of salt - changes and these changes, small as they may be, have large-scale effects on Earth's water cycle and ocean circulation.
Looking down on the oceans from high above, this animation depicts the day-by-day time evolution of sea surface salinities simulated by the NOAA GFDL CM2.6 climate model. One can see the interplay of fresh waters as they seek to exit the Arctic, moving southward along both sides of Greenland until they merge and circulate around the rim of the Labrador Sea. At the same time, higher salinity surface waters flow from the Gulf Stream extension, pass between Iceland and the British Isles, and enter the Nordic Seas. Icebergs are made of fresh frozen water, therefore, where icebergs form, sea surface salinity increases causing the water to increase in density. This high resolution model - the model grid cells are all smaller than 5 km (3.1 miles) on a side in the Arctic region - produces a wealth of eddies, which play a role in transport salt and heat in the ocean.
Ocean salinity is measured in PSU (practical salinity unit), grams of salt per 1000 grams of water.
C1 Patterns. Students identify similarities and differences in order to sort and classify natural objects and designed products. They identify patterns related to time, including simple rates of change and cycles, and to use these patterns to make predictions.
C3 Scale Proportion and Quantity. Students recognize natural objects and observable phenomena exist from the very small to the immensely large. They use standard units to measure and describe physical quantities such as weight, time, temperature, and volume.
C1 Patterns. Students recognize that macroscopic patterns are related to the nature of microscopic and atomic-level structure. They identify patterns in rates of change and other numerical relationships that provide information about natural and human designed systems. They use patterns to identify cause and effect relationships, and use graphs and charts to identify patterns in data.
C3 Scale Proportion and Quantity. Students observe time, space, and energy phenomena at various scales using models to study systems that are too large or too small. They understand phenomena observed at one scale may not be observable at another scale, and the function of natural and designed systems may change with scale. They use proportional relationships (e.g., speed as the ratio of distance traveled to time taken) to gather information about the magnitude of properties and processes. They represent scientific relationships through the use of algebraic expressions and equations
C5 Energy and Matter. Students learn matter is conserved because atoms are conserved in physical and chemical processes. They also learn within a natural or designed system, the transfer of energy drives the motion and/or cycling of matter. Energy may take different forms (e.g. energy in fields, thermal energy, energy of motion). The transfer of energy can be tracked as energy flows through a designed or natural system.
C1 Patterns. Students observe patterns in systems at different scales and cite patterns as empirical evidence for causality in supporting their explanations of phenomena. They recognize classifications or explanations used at one scale may not be useful or need revision using a different scale; thus requiring improved investigations and experiments. They use mathematical representations to identify certain patterns and analyze patterns of performance in order to re-engineer and improve a designed system.
C5 Energy and Matter. Students learn that the total amount of energy and matter in closed systems is conserved. They can describe changes of energy and matter in a system in terms of energy and matter flows into, out of, and within that system. They also learn that energy cannot be created or destroyed. It only moves between one place and another place, between objects and/or fields, or between systems. Energy drives the cycling of matter within and between systems. In nuclear processes, atoms are not conserved, but the total number of protons plus neutrons is conserved.
C7 Stability and Change. Students understand much of science deals with constructing explanations of how things change and how they remain stable. They quantify and model changes in systems over very short or very long periods of time. They see some changes are irreversible, and negative feedback can stabilize a system, while positive feedback can destabilize it. They recognize systems can be designed for greater or lesser stability
ESS2.A Earth Materials and Systems. Four major Earth systems interact. Rainfall helps to shape the land and affects the types of living things found in a region. Water, ice, wind, organisms, and gravity break rocks, soils, and sediments into smaller pieces and move them around
ESS2.C The Roles of Water in Earth's Processes. Most of Earth’s water is in the ocean and much of the Earth’s fresh water is in glaciers or underground.
ESS2.D Weather & Climate. Climate describes patterns of typical weather conditions over different scales and variations. Historical weather patterns can be analyzed so that they can make predictions about what kind of weather might happen next.
ESS2.A Earth Materials and Systems. Energy flows and matter cycles within and among Earth’s systems, including the sun and Earth’s interior as primary energy sources. Plate tectonics is one result of these processes.
ESS2.C The Roles of Water in Earth's Processes. Water cycles among land, ocean, and atmosphere, and is propelled by sunlight and gravity. Density variations of sea water drive interconnected ocean currents. Water movement causes weathering and erosion, changing landscape features.
ESS2.D Weather & Climate. Complex interactions determine local weather patterns and influence climate, including the role of the ocean.
ESS3.D Global Climate Change. Human activities affect global warming. Decisions to reduce the impact of global warming depend on understanding climate science, engineering capabilities, and social dynamics.
PS1.A Structure of Matter. The fact that matter is composed of atoms and molecules can be used to explain the properties of substances, diversity of materials, states of matter, phase changes, and conservation of matter.
ESS2.A Earth Materials and Systems. Feedback effects exist within and among Earth’s systems.The geological record shows that changes to global and regional climate can be caused by interactions among changes in the sun’s energy output or Earth’s orbit, tectonic events, ocean circulation, volcanic activity, glaciers, vegetation, and human activities.
ESS2.C The Roles of Water in Earth's Processes. The planet’s dynamics are greatly influenced by water’s unique chemical and physical properties.
ESS2.D Weather & Climate. The role of radiation from the sun and its interactions with the atmosphere, ocean, and land are the foundation for the global climate system. Global climate models are used to predict future changes, including changes influenced by human behavior and natural factors
ESS3.D Global Climate Change. Global climate models used to predict changes continue to be improved, although discoveries about the global climate system are ongoing and continually needed.
PS1.B Chemical Reactions. Chemical processes are understood in terms of collisions of molecules, rearrangement of atoms, and changes in energy as determined by properties of elements involved.