Knowing how much heat is stored in the ocean, how fast the sea levels are rising and sea ice is melting, is essential to understanding the current state and changes in the ocean and climate. This information is critical for assessing and confronting oceanic and atmospheric changes associated with global warming and they can be used by scientists, decision-makers, environmental agencies, the general public, and in measuring our responses to environmental directives. The OMIs expand the Copernicus Marine Service portfolio to provide not only ocean data products but also key reference information on the state of the ocean.
The Ocean Monitoring Indicators are free and available on the Copernicus Marine Service website as digital files (click here). They include observations starting in 1993, hindcast and forecast data of global and regional ocean heat content, the global mean and regional sea level, and the Antarctic and Arctic sea ice extent (the Arctic time series is from 1979 onwards). These three variables are extracted from the Copernicus Marine Service Ocean State Report because they represent the oceanic symptoms of a heated planet. These trends were found to be of particular importance in the Copernicus Marine Service Ocean State Report, an annual peer-reviewed publication that provides scientific context and a thorough analysis on the state of the ocean, trends, and severe/notable events (the 2018 report will be published in the coming months). The OMI products were developed through a long process of scientific analysis and validation, with the consensus of around 100 Copernicus Marine Service scientific experts after their review. The OMIs were created through a strong collaboration with other Copernicus services such as the Copernicus Climate Change Service (C3S).
Following various Earth observation initiatives like those of NASA and NOAA in the USA, the Copernicus Marine Service independently produced the OMIs, as a part of the European Union’s Copernicus Programme, the world’s single largest Earth observation programme. The data is based on historical satellite and in situ observations of the ocean and sea ice as well as numerical ocean models.
The key findings of the Copernicus Marine Service OMIs and Ocean State Report:
Global mean sea level rise amounts to 3.4 millimeters per year from 1993 to 2016 (with an uncertainty of ±0.5mm/year). About 30% of global sea level rise can be attributed to ocean thermal expansion due to the ocean warming.
What does this mean for us? Sea level rise is caused primarily by two factors related to global warming: the added water from melting ice sheets and glaciers and the expansion of sea water as it warms. When water is heated it expands, this is called thermal expansion, a phenomena that we are seeing more of as the ocean consistently warms over the past decades. Sea level rise can seriously effect human populations in coastal and island regions and natural environments like marine ecosystems. The impacts can be wide-ranging and can include: increased coastal erosion, higher storm-surge flooding, inhibition of primary production processes, more extensive coastal inundation, changes in surface water quality and groundwater characteristics, increased loss of property and coastal habitats, increased flood risk and potential loss of life, loss of non-monetary resources and value, impact on agriculture and aquaculture through decline in soil and water quality, loss of tourism, recreation, and transportation functions.
The upper global ocean has continuously warmed since 1993 at a rate of 0.8 ±0.1 Watts per meters squared (with an uncertainty of ±0.1 watts/m2). More than 40% of this subsurface warming can be attributed to heat storage in the 700-2000m depth layer.
What does this mean for us? Variations in the ocean heat content can induce changes in ocean stratification, currents, sea ice and ice shelfs. A warming ocean causes thermal expansion (increasing sea level rise) and thermal stress that, for example, contributes to coral bleaching and infectious disease. A warming ocean can also cause altered ocean currents leading to changes in atmosphere and sea connectivity and temperature exchange. It is important to monitor the ocean’s ability to store and exchange heat with the atmosphere, as it in turn influences the Earth’s climate and atmospheric patterns from a local to global scale. One such example is the naturally occurring heat exchanges during El Nino Southern Oscillations (ENSO) events.
Following a prominent sea ice decrease in the Antarctic Ocean in 2016, both the Antarctic and the Arctic oceans are currently at record lows in terms of sea ice extent. Since 1993 in the Arctic Ocean, the sea ice extent has decreased significantly at an annual rate of -0.78*106 km2 per decade. Ten of the lowest Arctic summer sea ice extent values took place in the last ten years. Since 1993 in the Antarctic Ocean, the annual sea ice extent has slightly increased at a rate of 0.21*106 km2 per decade. However, in the last quarter of 2016, there was a record-setting rapid loss of Antarctic ice starting in early September.
What does this mean for us? Variations in sea ice cover can induce changes in ocean stratification, in global and regional sea level rates, and modify the key role played by the cold poles in the Earth engine. This can include effects on thermal convections and the climate sea interactions. There can be many consequences to melting Arctic ice caps, from shifts in the ecosystem to changing human behaviors, such as a likely increase in boat traffic through the Arctic Ocean. During warm years when there is early sea ice retreat, there can be an impact on the annual net oceanic primary production through phytoplankton blooms. It can also impact wildlife. Polar bears, for instance, have to find alternative food sources because of scarcities caused by the Arctic sea ice that melts earlier and freezes later each year.