Poleward shifts of oceanic boundary currents. From: Hydro International

by Bethany Woo

Every species has specific habitat preferences or requirements that it needs to survive and thrive. For marine and oceanic species, these requirements may include certain water-column depths, dissolved oxygen levels, salinity, water temperatures, water pH, and wave exposure. The geographic area in which all these environmental preferences are met is the species’ range. 

However, oceanic conditions are shifting away from historic conditions due to the effects of climate change. The greatest or most noticeable effects have been increases in the ocean surface water temperatures and water acidity (pH). One result of changing ocean conditions is that species’ ranges are also moving. Based on a species’ preferences and ability to tolerate different environmental conditions, their range can shift, expand, or contract. For species that prefer or can tolerate warmer water temperatures, they may experience range expansion, or an increase in potential habitat area compared to the historic range. Species that require more specific conditions or cannot tolerate change may experience range reduction. A common range shift for these species is toward the North or South poles, where water temperatures are cooler, and away from the equator, where water temperatures are warmer.

Due to the migratory nature of many marine species and the vastness of the ocean, it is difficult to study and confirm the degree of range shifts and the rate at which they occur. Range shifts in marine species only recently began to gain greater traction in scientific research in the 21st century. However, as range shifts may have cascading effects on the stability of marine environments, global fishing industries, and global ecotourism, researching range shifts is essential to understand the consequences of climate change.

Sources

https://www.researchgate.net/publication/378091294_Species_range_shifts_biological_invasions_and_ocean_warming

https://www.redmap.org.au/article/marine-species-are-on-the-move--but-what-exactly-is-a-range-shift/

https://www.annualreviews.org/content/journals/10.1146/annurev-marine-010419-010916

https://www.hydro-international.com/content/news/intensification-and-poleward-shift-of-oceanic-boundary-currents

The Cod Icefish. From: Wikipedia

by Madeline McCormick

The first snow of the season has fallen, and as temperatures drop we begin to prepare ourselves by stoking the fire, bundling up in wool blankets, and clutching a mug of whatever hot beverage we’re craving. But do you ever wonder how marine species living in the most extreme environments stave off the cold with nothing but their own biology as a defense? This month we are going to be talking about the Icefish, a species that calls the Southern Antarctic Ocean home. As a clarifying statement, this article will focus on the family of cod icefishes Nototheniidae, rather than the south oceanic Crocodile Icefish (Channichthyidae), or the Noodlefish (Salangidae), an Eastern Asian transparent family of fishes. Cod Icefishes have a few unique evolutionary specializations that permit them to live in waters that would freeze most other species. The mean water temperature of the Antarctic is around 28-32 degrees Fahrenheit—capable of freezing a human within minutes—and highly oxygenated. An evolutionary trade-off was made around 47 million years ago when the presence of hemoglobin, a common protein that facilitates oxygen intake in blood cells, was sacrificed and replaced with Antifreeze Glycoprotein (AFGP), which restricts the formation of ice crystals and protects cells and tissues. There are several other notable selected traits, such as larger hearts to pump less-oxygenated blood quicker, fatty tissues to insulate and regulate body density in the absence of a swim bladder, etc.

https://academic.oup.com/mbe/article/40/3/msad029/7035026?login=false

https://www.igb.illinois.edu/article/cold-specialized-icefish-species-underwent-major-genetic-changes-it-migrated-temperate

https://en.wikipedia.org/wiki/Nototheniidae 

https://academic.oup.com/mbe/article/40/11/msad236/7329987#:~:text=Antarctic%20fish%20of%20the%20suborder,;%20DeVries%20and%20Cheng%202005)

by Trevor Regan

Perhaps the most defining feature of our polar regions, glaciers are a pivotal component of our oceans and waterways. Fresh glacier water feeds rivers and lakes—water that we drink, and water that freshwater fish thrive in. The nutrients they disperse into the ocean feed coastal phytoplankton, the foundation of many marine ecosystems, while whales, polar bears, seals, sharks, and salmon call the hundreds-of-feet-high cliff faces home.

These colossal landforms begin with a single snowflake, and then countless more. Enough snowfall has to survive summertime melting to allow a buildup in a mountain range (ice field and cirque glaciers), valley (valley glacier), or along a coastline (piedmont and tidewater glaciers). As new snow falls, the lower layers will be weighed down and packed first into coarse-grained snow and then into firn, both of which resemble starfish. While a typical snowflake is 90% air, coarse-grained snow and firn are 50% and 30% air, respectively. Decades and often centuries of further compression turn what were once snowflakes into dense particles of bright blue glacier ice.   

The tremendous weight of glaciers, especially those in mountain ranges, means that gravity is always pulling them downward. In overhead pictures, they even look like a frozen river or a flowing current of snow. And as with rivers, the places where glaciers meet the sea are hubs of activity. Calving, shown here with the Grey Glacier in Chile, occurs most frequently on tidewater glaciers. These seismic events are caused by glacier movement, tides, and warm waters. Blocks and entire sections of ice separate from the glacier, crashing, collapsing, and capsizing, generating tidal waves and earthquakes. Dry calving, which occurs among inland glaciers, causes avalanches. In 2008, Adam LeWinter and Jeff Orlowski filmed the largest calving event ever recorded at Illusissat Glacier in Greenland for the documentary Chasing Ice (2012). A three-mile-wide face standing 300 to 400 feet above water retreated a mile. The event lasted over an hour. 

Calving events are occurring more frequently than ever before. As James Balog explained in Chasing Ice, the Illusissat Glacier retreated nine miles between 2001 and 2010. Between 1902 and 2001, it had retreated eight miles. Glacial decline is not only a consequence of climate change but also a cause, as they help regulate the Earth’s temperature by reflecting sunlight off their snow-white surfaces. With fewer glaciers, the planet absorbs more heat, ocean temperatures increase, and more glaciers melt. Alongside the dramatic decline of ice sheets, glacier loss is a main contributor to the threat of rising sea levels. 


Sources

https://www.antarcticglaciers.org/glacier-processes/mass-balance/firn-and-firn-aquifers/

https://www.earthdata.nasa.gov/topics/cryosphere/glaciers/glacier-power/how-do-glaciers-form

https://www.earthdata.nasa.gov/topics/cryosphere/glaciers/glacier-power/what-is-glacial-calving

https://www.youtube.com/watch?v=hC3VTgIPoGU

https://www.youtube.com/watch?v=RVwLHX6lgzQ

https://www.antarcticglaciers.org/glacier-processes/glacial-lakes/calving-of-freshwater-glaciers/