...
Such regular calvings are just part of the natural seasonal variations and no evidence of any drama in terms of "more ice-climate feedback mechanisms than assumed in any CMIP6 model (including in E3SM1)"
Hefaistos,
I have made well over a thousand posts specifically providing evidence that there is '… drama in terms of "more ice-climate feedback mechanisms than assumed in any CMIP6 model (including in E3SM1)"; however, I acknowledge that the topic of potential abrupt climate change this century is complex & thus potentially confusing to many readers, such as by your posts apparent effort to tie Greenland Surface Mass Balance, SMB, to ice-climate feedback mechanisms; whereas in reality Greenland SMB is more related to sea level rise than to ice-climate feedback mechanism; while ice-climate feedback is more related to surface ice melting together with ice calving.
Therefore, while readers potentially confused by your post could scroll back through this thread (and/or my posts on this topic in other threads) to find evidence of more ice-climate feedback mechanism than those assumed in E3SM1; I will provide a few simple lines of such evidence in this post.
I begin with the first linked Wikipedia article on the North Atlantic Cold Blob (see the first attached image) that indicates that Mann and Rahmstorf were among to the first to suggest that this North Atlantic Cold Blob is likely created by global warming-induced meltwater primarily from Greenland, and that this blob is contributing to the observed slowdown of the AMOC (MOC).
Title: "Cold blob (North Atlantic)"
https://en.wikipedia.org/wiki/Cold_blob_(North_Atlantic)
Extract: "The cold blob in the North Atlantic (also called the North Atlantic warming hole) describes a cold temperature anomaly of ocean surface waters, affecting the Atlantic Meridional Overturning Circulation (AMOC) which is part of the thermohaline circulation, possibly related to global warming-induced melting of the Greenland ice sheet.
…
Climate scientists Michael Mann of Penn State and Stefan Rahmstorf from the Potsdam Institute for Climate Impact Research suggested that the observed cold pattern during years of temperature records is a sign that the Atlantic Ocean's Meridional overturning circulation (AMOC) may be weakening.
Next, I provide the second link to a Wikipedia article on abrupt climate change that indicates that:
"
… a variety of tipping elements could reach their critical point within this century under anthropogenic climate change".
It has been postulated that teleconnections, oceanic and atmospheric processes, on different timescales, connect both hemispheres during abrupt climate change."
Title: "Abrupt climate change"
https://en.wikipedia.org/wiki/Abrupt_climate_changeExtract: "Possible tipping elements in the climate system include regional effects of global warming, some of which had abrupt onset and may therefore be regarded as abrupt climate change. Scientists have stated, "Our synthesis of present knowledge suggests that a variety of tipping elements could reach their critical point within this century under anthropogenic climate change".
It has been postulated that teleconnections, oceanic and atmospheric processes, on different timescales, connect both hemispheres during abrupt climate change."
In this regard, I provide the second attached image that illustrates one of many teleconnection be both hemispheres (related to the bipolar seesaw mechanism), that shows how an acceleration of the Westerly winds over the Southern Ocean (e.g. due to the Antarctic ozone hole and/or to increased atmospheric GHG concentrations) has increased Agulhas Leakage that is also working to cool the North Atlantic; which is also slowing the AMOC (just like the North Atlantic Cold Blob associated with Greenland meltwater).
Next, I provide the third attached image that shows how anthropogenically-induced Antarctic meltwater is currently inhibiting the cooling of Antarctic Circumpolar Deep Water (CDW); which, provides yet another ice-climate feedback mechanism to increase the future temperature of the CDW beneath Antarctic ice shelves and grounding lines for marine glaciers that then lead to a feedback loop for more ice melting and more warming of the CDW. This image projects a significant amount of warming of the CDW between 2040 and 2050 at water depth that could contribute to potential future MICI-types of failures for key West Antarctic marine glaciers like the PIG and the Thwaites Glacier.
Next the following linked reference's finding that part of the E3SM version 1 projected high value of TCR (see the fourth image) is due to a projected slowing of the AMOC; then this may well be because E3SM version 1 did a better job of evaluating the influence of freshwater hosing from glacier meltwater; then this implies that ice-climate feedbacks may likely have a much higher impact on increasing climate sensitivity than consensus climate science is currently acknowledging.
Aixue Hu et al. (17 April 2020), "Role of AMOC in transient climate response to greenhouse gas forcing in two coupled models", Journal of Climate,
https://doi.org/10.1175/JCLI-D-19-1027.1https://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-19-1027.1?af=RAbstract
As the greenhouse gas concentrations increase, a warmer climate is expected. However, numerous internal climate processes can modulate the primary radiative warming response of the climate system to rising greenhouse gas forcing. Here the particular internal climate process that we focus on is the Atlantic Meridional Overturning Circulation (AMOC) – an important global scale feature of ocean circulation that serves to transport heat and other scalars, and we address the question of how the mean strength of AMOC can modulate the transient climate response. While the Community Earth System Model version 2 (CESM2) and the Energy Exascale Earth System Model version 1 (E3SM1) have very similar equilibrium/effective climate sensitivity, our analysis suggests that a weaker AMOC contributes in part to the higher transient climate response to a rising greenhouse gas forcing seen in E3SM1 by permitting a faster warming of the upper ocean and a concomitant slower warming of the subsurface ocean. Likewise the stronger AMOC in CESM2 by permitting a slower warming of the upper ocean leads in part to a smaller transient climate response. Thus, while the mean strength of AMOC does not affect the equilibrium/effective climate sensitivity, it is likely to play an important role in determining the transient climate response on the centennial timescale.
Finally, I note that the following linked reference, and associated linked article, concludes that Antarctic glacial meltwater is a 'climate response function' (CRF) that improves climate model projections (as currently consensus climate models ignore this CRF). Furthermore, readers should be aware that James Hansen has previously identified this CRF as a positive ice-climate feedback mechanism that accelerates climate change:
“Antarctic Glacial Melt as a Driver of Recent Southern Ocean Climate Trends” by Craig D. Rye, John Marshall, Maxwell Kelley, Gary Russell, Larissa S. Nazarenko, Yavor Kostov, Gavin A. Schmidt and James Hansen, 9 April 2020, Geophysical Research Letters; DOI: 10.1029/2019GL086892
https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL086892Abstract
Recent trends in Southern Ocean (SO) climate—of surface cooling, freshening, and sea ice expansion—are not captured in historical climate simulations. Here we demonstrate that the addition of a plausible increase in Antarctic meltwater to a coupled climate model can produce a closer match to a wide range of climate trends. We use an ensemble of simulations of the Goddard Institute for Space Studies Earth system model to compute “climate response functions” (CRFs) for the addition of meltwater. These imply a cooling and freshening of the SO, an expansion of sea ice, and an increase in steric height, all consistent with observations since 1992. The CRF framework allows one to compare the efficacy of Antarctic meltwater as a driver of SO climate trends, relative to greenhouse gas and surface wind forcing. The meltwater CRFs presented here strongly suggest that interactive Antarctic ice melt should be included in climate models.
Plain Language Summary
Climate models do not capture recent Southern Ocean (SO) climate trends of surface cooling, freshening, and sea ice expansion. Here we demonstrate that including a realistic increase in Antarctic meltwater can improve a model's representation of SO trends. We use an ensemble of simulations of the Goddard Institute for Space Studies Earth system model. Model results suggest that Antarctic meltwater drives a cooling and freshening of the SO and an expansion of winter sea ice, all consistent with observations. Results suggest that a better representation of Antarctic ice melt should be included in climate models.
See also:
Title: "Melting Glaciers Cool the Southern Ocean – Might Explain the Recent Antarctic Cooling and Sea Ice Expansion"
https://scitechdaily.com/melting-glaciers-cool-the-southern-ocean-might-explain-the-recent-antarctic-cooling-and-sea-ice-expansion/Extract: "Research suggests glacial melting might explain the recent decadal cooling and sea ice expansion across Antarctica’s Southern Ocean.
Tucked away at the very bottom of the globe surrounding Antarctica, the Southern Ocean has never been easy to study. Its challenging conditions have placed it out of reach to all but the most intrepid explorers. For climate modelers, however, the surface waters of the Southern Ocean provide a different kind of challenge: It doesn’t behave the way they predict it would. “It is colder and fresher than the models expected,” says Craig Rye, a postdoc in the group of Cecil and Ida Green Professor of Oceanography John Marshall within MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS).
In recent decades, as the world warms, the Southern Ocean’s surface temperature has cooled, allowing the amount of ice that crystallizes on the surface each winter to grow. This is not what climate models anticipated, and a recent study published in Geophysical Research Letters attempts to disentangle that discrepancy. “This paper is motivated by a disagreement between what should be happening according to simulations and what we observe,” says Rye, the lead author of the paper who is currently working remotely from NASA’s Goddard Institute for Space Studies, or GISS, in New York City.
…
When this increase in glacial melt was added to the model, it led to sea surface cooling, decreases in salinity, and expansion of sea ice coverage that are consistent with observed trends in the Southern Ocean during the last few decades. Their model results suggest that meltwater may account for the majority of previously misunderstood Southern Ocean cooling.
The model shows that a warming climate may be driving, in a counterintuitive way, more sea ice by increasing the rate of melting of Antarctica’s glaciers. According to Marshall, the paper may solve the disconnect between what was expected and what was observed in the Southern Ocean, and answers the conundrum he and Kostov pointed to in 2016. “The missing process could be glacial melt.”"
