Arctic News: latent heat buffer

Showing posts with label latent heat buffer. Show all posts

Wednesday, September 3, 2025

Arctic sea ice September 2025

The image below shows Arctic sea ice concentration on September 9, 2025.

Over the years, the global monthly sea ice concentration has fallen significantly (compared to 1951-1980). The image below shows the global monthly sea ice concentration anomaly through August 2025.

Albedo loss due to very low global sea ice area

The global sea ice area was 2.50 million km² below the 1981-2010 mean on September 10, 2025, a deviation from 1981-2010 of -4.32σ.

The above image shows the situation through September 9, 2025. It is significant that the global sea ice area anomaly has been strongly negative this year, even despite the absence of an El Niño.

Sea ice decline can occur by reduction in the area covered by the sea ice, resulting in albedo loss. Sea ice decline can also occur as the sea ice darkens, which can occur due to melting, cracking and thinning of the ice, due to rain and meltwater forming pools on top of the ice, due to growth of algae and due to settling down of aerosols on the sea ice, all of which will also result in albedo loss.

Loss of sea ice area results in albedo loss, which means that less sunlight gets reflected back into space and more heat instead gets absorbed by the ocean.

[ image from earlier post ]

Arctic sea ice thickness and volume

Sea ice decline also occurs as a result of thinning of the sea ice. The image on the right shows Arctic sea ice thickness on September 11, 2025.

Sea ice thickness can be hard to measure, due to rain and meltwater forming pools on top of the ice, while clouds can also obscure satellite imaging.

On the image below, adapted from dmi.dk, markers are added for September (red) and April (blue) corresponding with the year's minimum- and maximum volume, showing the downward path over the years for both the annual sea ice volume minimum and maximum. Magenta bars are added in years when the melting volume from April to September was large, while green bars are added in years when it was small.

Arctic sea ice volume in April 2025 was about 19,000 km³, which raised fears that virtually all Arctic sea ice could disappear in September 2025, resulting in a Blue Ocean Event.

Meanwhile, sea ice volume has fallen to about 4,000 km³ on September 12, 2025, as illustrated by the image below. Arctic sea ice volume was at a record low for the day on September 15, 2025, as it has been for more than a year.

Why a Blue Ocean Event is so dangerous

PIOMAS estimates that 16,400 km³ of ice is lost every year (1979-2010 average) from April to September, consuming an amount of energy of 5 x 10²¹ Joules (the image on the right shows calculations, click on this link or on the image to enlarge).

Once the latent heat buffer is lost, further heat must go elsewhere. During the phase change from ice to water, the temperature doesn't rise, i.e. all the energy goes into the process of changing ice into water. Once all ice has melted, further heat will raise the temperature of the water. The amount of energy that is consumed in the process of melting the ice is as much as it takes to heat an equivalent mass of water from zero°C to 80°C.

Decline of the snow and ice cover comes with numerous feedbacks, the loss of the latent heat buffer (feedback #14 on the feedbacks page) is only one of them. Further feedbacks include the loss of albedo (feedback #1), increases in emissions (feedback #2), loss of emissivity (feedback #23), while there are also changes to the Jet Stream (feedback #14) and changes to clouds and water vapor (feedback #20), and there are mechanisms and circumstances aggravating the danger, such as the slowdown of AMOC and further changes to ocean currents.

Eruption of methane from the seafloor of the Arctic Ocean (feedback #16) is one of the most dangerous feedbacks. As the seafloor of the Arctic Ocean heats up, heat can penetrate sediments and cause destabilization of hydrates, resulting in eruption of methane. As the seas in the Arctic Ocean can be very shallow, the methane can erupt with force in the form of plumes, with little opportunity for the methane to get decomposed in the water. Furthermore, there is very little hydroxyl in the air over the Arctic, which extends the lifetime of methane over the Arctic.

[ The Buffer is gone, from Accelerating Temperature Rise ]

Sea ice constitutes a buffer that previously consumed much incoming ocean heat (left); as sea ice thins, the buffer disappears while more heat also enters the Arctic Ocean (right). Further heat entering the Arctic Ocean from the Atlantic Ocean and the Pacific Ocean threatens to destabilize sediments that contain methane, causing eruption of huge amounts of methane.

The image below, adapted from an image issued by NOAA on September 16, 2025, shows hourly methane averages recorded at the Barrow Atmospheric Baseline Observatory (BRW), a NOAA facility located near Utqiaġvik (formerly Barrow), Alaska, at 71.32 degrees North.

The image below, adapted from Copernicus, shows a methane forecast for September 6, 2025 12:00, run that day at 00 UTC. High methane levels are visible on the West Coast of Canada, also discussed on facebook.

The image below shows that the NOAA 21 satellite recorded methane levels as high as 2559 parts per billion (ppb) at 399.1 mb on September 6, 2025 AM.

High temperatures and ocean heat

In August 2025, high temperature anomalies (compared to 1951-1980) were recorded at both poles, as illustrated by the image below.

The image below shows the NASA August 2025 temperature anomaly (versus 1951_1980).

Ominously, the global temperature anomaly has gone up again recently, despite the current absence of an El Niño. The anomaly for August 2025 was 1.51°C above 1903-1912 (not pre-industrial), as illustrated by the image below.

The image below shows temperature anomalies from 1951-1980 (NCEP/NCAR data).

The image below shows sea surface temperature anomalies through August 2025 (ERA5 Data).

The image below shows NASA land-only anomalies from 1880-1920 (not pre-industrial) through August 2025, when the anomaly was 1.82°C. The red line is a 3-year Lowess Smoothing trend. If this trend continued unchanged (dashed red), the anomaly could cross 3°C in 2029, causing mass extinction.

Note that when using a genuinely pre-industrial base, anomalies can be much higher than depicted in the above images. A 3°C anomaly constitutes an important threshold, since humans will likely go extinct with such a rise. As illustrated by the image below, the rise may already be more well over 2°C, while we may face a potentially huge temperature rise over the next few years.

[ from the post When will humans go extinct? ]

[ from: When Will We Die? ]

Recent research led by David Fastivich finds that, historically, vegetation responded at timescales from hundreds to tens of thousands of years, but not at timescales shorter than about 150 years. It takes centuries for tree populations to adapt - far too slow to keep pace with today’s rapidly warming world.

Note that healthy vegetation relies not only on temperature, but also on the presence of good soil, microbes, rain, soil nutrients, pollinators, habitat, groundwater and an absence of toxic waste, pests and diseases.

A 2018 study by Strona & Bradshaw indicates that most life on Earth will disappear with a 5°C rise (see box on the right). Humans, who depend on a lot of other species, will likely go extinct with a 3°C, as discussed in the earlier post When Will We Die?

The image below shows Arctic air temperature through September 5, 2025, with the inset highlighting the Arctic and the global temperature anomaly that day. The temperature in the Arctic reached a daily record high of 2.4°C on September 5, 2025, an anomaly of +2.46°C compared to 1979-2000.

The image below shows sea surface temperatures in the Gulf through September 7, 2025, when the sea surface reached a record daily high temperature of an average of 30.84°C, an anomaly of +1.53°C compared to 1982-2010, with the inset highlighting the Gulf and the global sea surface temperature anomaly that day.

The image below shows high Ocean Heat Content in the Gulf through September 7, 2025.

Equivalent Ocean Heat Content on September 8, 2025, is illustrated in the image below.

The temperature of the ocean is very high in many areas, as illustrated by the image below. The image below shows sea surface temperatures around North America as high as 33°C on September 1, 2025.

In conclusion, a lot of ocean heat is still on its way toward the Arctic Ocean along the path of the Gulf Stream.

The Jet Stream is getting increasingly distorted, which threatens to - at times - speed up the flow of large amounts of heat into the Arctic Ocean. The image below shows the situation on September 10, 2025.

The image on the left shows the Jet Stream following the path of the Gulf Stream over the North Atlantic, with one branch going south and moving backward, while another branch is moving North over the Arctic Ocean, with both branches displaying circular patterns.

The image on the right shows the Jet Stream reaching speeds over the Arctic Ocean as high as 253 km/h with wind power density as high as 67.9 kW/m² (at the green circle).

Land Evaporation Tipping Point

Higher temperatures come with stronger feedbacks, such as stronger evaporation resulting in both a lot more water vapor and a lot more heat getting transferred from the surface to the atmosphere. Much of this will return to the surface with precipitation such as rain and snow, but 7% more water vapor will end up in the atmosphere for every degree Celsius rise in temperature. Moreover, water vapor is a potent greenhouse gas that will increase temperatures and it is a self-amplifying feedback that can strongly contribute to further acceleration of the temperature rise.

Precipitable water can be expressed in kg/m² or in millimeters (mm), with the latter representing the depth of the water if all the atmospheric vapor were condensed into liquid form and spread across the surface, while kilograms per square meter (kg/m²) represents the mass of that water per unit area (1 kg/m² = 1 mm). As illustrated by the image below, the monthly precipitable water anomaly (in kg/m², versus 1951-1980) has increased over time, in line with rising temperatures.

At the same time, the monthly total precipitation anomaly (versus 1951-1980) has decreased over time, as illustrated by the image below.

This decrease in precipitation indicates that over time, less and less evaporation is taking place over land, in turn indicating that the Land Evaporation Tipping Point is getting crossed in areas where water is no longer available locally for further evapotranspiration, i.e. from all processes by which water moves from the land surface to the atmosphere via evaporation and transpiration, including transpiration from vegetation, evaporation from the soil surface, from the capillary fringe of the groundwater table, and from water bodies on land, as also discussed at this page and at this article on the Water Vapor-Pressure Deficit (VPD).

Once this tipping point gets crossed, the land and atmosphere will heat up strongly. Additionally, more water vapor in the atmosphere accelerates the temperature rise, since water vapor is a potent greenhouse gas and this also contributes to speeding up the temperature rise of the atmosphere (as also discussed on facebook here, here and here).

The image below, adapted from Copernicus, shows the global fall in relative humidity over land over time.

[ image from Moistening Atmosphere ]

Climate Emergency Declaration

The temperature rise is accelerating and the rise could accelerate even more due to decreases in buffers (as described in earlier posts such as this one), due to strengthening feedbacks, especially during an El Niño, and due to further reduction of the aerosol masking effect, which are all developments that could rapidly speed up existing feedbacks and trigger new feedbacks.

The situation is dire and the precautionary principle calls for rapid, comprehensive and effective action to reduce the damage and to improve the situation, as described in this 2022 post, where needed in combination with a Climate Emergency Declaration, as discussed at this group.